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freebsd-skq/sys/kern/kern_umtx.c

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- Add an api for doing smp safe locks in userland. - umtx_lock() is defined as an inline in umtx.h. It tries to do an uncontested acquire of a lock which falls back to the _umtx_lock() system-call if that fails. - umtx_unlock() is also an inline which falls back to _umtx_unlock() if the uncontested unlock fails. - Locks are keyed off of the thr_id_t of the currently running thread which is currently just the pointer to the 'struct thread' in kernel. - _umtx_lock() uses the proc pointer to synchronize access to blocked thread queues which are stored in the first blocked thread.
2003-04-01 01:10:42 +00:00
/*
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
* Copyright (c) 2004, David Xu <davidxu@freebsd.org>
- Add an api for doing smp safe locks in userland. - umtx_lock() is defined as an inline in umtx.h. It tries to do an uncontested acquire of a lock which falls back to the _umtx_lock() system-call if that fails. - umtx_unlock() is also an inline which falls back to _umtx_unlock() if the uncontested unlock fails. - Locks are keyed off of the thr_id_t of the currently running thread which is currently just the pointer to the 'struct thread' in kernel. - _umtx_lock() uses the proc pointer to synchronize access to blocked thread queues which are stored in the first blocked thread.
2003-04-01 01:10:42 +00:00
* Copyright (c) 2002, Jeffrey Roberson <jeff@freebsd.org>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice unmodified, this list of conditions, and the following
* disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
Use __FBSDID().
2003-06-11 00:56:59 +00:00
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
- Add an api for doing smp safe locks in userland. - umtx_lock() is defined as an inline in umtx.h. It tries to do an uncontested acquire of a lock which falls back to the _umtx_lock() system-call if that fails. - umtx_unlock() is also an inline which falls back to _umtx_unlock() if the uncontested unlock fails. - Locks are keyed off of the thr_id_t of the currently running thread which is currently just the pointer to the 'struct thread' in kernel. - _umtx_lock() uses the proc pointer to synchronize access to blocked thread queues which are stored in the first blocked thread.
2003-04-01 01:10:42 +00:00
#include <sys/param.h>
#include <sys/kernel.h>
Change the thread ID (thr_id_t) used for 1:1 threading from being a pointer to the corresponding struct thread to the thread ID (lwpid_t) assigned to that thread. The primary reason for this change is that libthr now internally uses the same ID as the debugger and the kernel when referencing to a kernel thread. This allows us to implement the support for debugging without additional translations and/or mappings. To preserve the ABI, the 1:1 threading syscalls, including the umtx locking API have not been changed to work on a lwpid_t. Instead the 1:1 threading syscalls operate on long and the umtx locking API has not been changed except for the contested bit. Previously this was the least significant bit. Now it's the most significant bit. Since the contested bit should not be tested by userland, this change is not expected to be visible. Just to be sure, UMTX_CONTESTED has been removed from <sys/umtx.h>. Reviewed by: mtm@ ABI preservation tested on: i386, ia64
2004-07-02 00:40:07 +00:00
#include <sys/limits.h>
- Add an api for doing smp safe locks in userland. - umtx_lock() is defined as an inline in umtx.h. It tries to do an uncontested acquire of a lock which falls back to the _umtx_lock() system-call if that fails. - umtx_unlock() is also an inline which falls back to _umtx_unlock() if the uncontested unlock fails. - Locks are keyed off of the thr_id_t of the currently running thread which is currently just the pointer to the 'struct thread' in kernel. - _umtx_lock() uses the proc pointer to synchronize access to blocked thread queues which are stored in the first blocked thread.
2003-04-01 01:10:42 +00:00
#include <sys/lock.h>
- Remove the blocked pointer from the umtx structure. - Use a hash of umtx queues to queue blocked threads. We hash on pid and the virtual address of the umtx structure. This eliminates cases where we previously held a lock across a casuptr call. Reviwed by: jhb (quickly)
2003-06-03 05:24:46 +00:00
#include <sys/malloc.h>
- Add an api for doing smp safe locks in userland. - umtx_lock() is defined as an inline in umtx.h. It tries to do an uncontested acquire of a lock which falls back to the _umtx_lock() system-call if that fails. - umtx_unlock() is also an inline which falls back to _umtx_unlock() if the uncontested unlock fails. - Locks are keyed off of the thr_id_t of the currently running thread which is currently just the pointer to the 'struct thread' in kernel. - _umtx_lock() uses the proc pointer to synchronize access to blocked thread queues which are stored in the first blocked thread.
2003-04-01 01:10:42 +00:00
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/sysent.h>
#include <sys/systm.h>
#include <sys/sysproto.h>
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
#include <sys/eventhandler.h>
- Add an api for doing smp safe locks in userland. - umtx_lock() is defined as an inline in umtx.h. It tries to do an uncontested acquire of a lock which falls back to the _umtx_lock() system-call if that fails. - umtx_unlock() is also an inline which falls back to _umtx_unlock() if the uncontested unlock fails. - Locks are keyed off of the thr_id_t of the currently running thread which is currently just the pointer to the 'struct thread' in kernel. - _umtx_lock() uses the proc pointer to synchronize access to blocked thread queues which are stored in the first blocked thread.
2003-04-01 01:10:42 +00:00
#include <sys/thr.h>
#include <sys/umtx.h>
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
#include <vm/vm.h>
#include <vm/vm_param.h>
#include <vm/pmap.h>
#include <vm/vm_map.h>
#include <vm/vm_object.h>
#define UMTX_PRIVATE 0
#define UMTX_SHARED 1
#define UMTX_STATIC_SHARED
struct umtx_key {
int type;
union {
struct {
vm_object_t object;
long offset;
} shared;
struct {
struct umtx *umtx;
long pid;
} private;
struct {
void *ptr;
long word;
} both;
} info;
};
- Remove the blocked pointer from the umtx structure. - Use a hash of umtx queues to queue blocked threads. We hash on pid and the virtual address of the umtx structure. This eliminates cases where we previously held a lock across a casuptr call. Reviwed by: jhb (quickly)
2003-06-03 05:24:46 +00:00
struct umtx_q {
LIST_ENTRY(umtx_q) uq_next; /* Linked list for the hash. */
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
struct umtx_key uq_key; /* Umtx key. */
1. Fix race condition between umtx lock and unlock, heavy testing on SMP can explore the bug. 2. Let umtx_wake returns number of threads have been woken.
2004-12-24 11:30:55 +00:00
struct thread *uq_thread; /* The thread waits on. */
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
LIST_ENTRY(umtx_q) uq_rqnext; /* Linked list for requeuing. */
vm_offset_t uq_addr; /* Umtx's virtual address. */
- Remove the blocked pointer from the umtx structure. - Use a hash of umtx queues to queue blocked threads. We hash on pid and the virtual address of the umtx structure. This eliminates cases where we previously held a lock across a casuptr call. Reviwed by: jhb (quickly)
2003-06-03 05:24:46 +00:00
};
LIST_HEAD(umtx_head, umtx_q);
1. use per-chain mutex instead of global mutex to reduce lock collision. 2. Fix two race conditions. One is between _umtx_unlock and signal, also a thread was marked TDF_UMTXWAKEUP by _umtx_unlock, it is possible a signal delivered to the thread will cause msleep returns EINTR, and the thread breaks out of loop, this causes umtx ownership is not transfered to the thread. Another is in _umtx_unlock itself, when the function sets the umtx to UMTX_UNOWNED state, a new thread can come in and lock the umtx, also the function tries to set contested bit flag, but it will fail. Although the function will wake a blocked thread, if that thread breaks out of loop by signal, no contested bit will be set.
2004-11-30 12:02:53 +00:00
struct umtxq_chain {
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
struct mtx uc_lock; /* Lock for this chain. */
struct umtx_head uc_queue; /* List of sleep queues. */
1. Fix race condition between umtx lock and unlock, heavy testing on SMP can explore the bug. 2. Let umtx_wake returns number of threads have been woken.
2004-12-24 11:30:55 +00:00
#define UCF_BUSY 0x01
#define UCF_WANT 0x02
int uc_flags;
1. use per-chain mutex instead of global mutex to reduce lock collision. 2. Fix two race conditions. One is between _umtx_unlock and signal, also a thread was marked TDF_UMTXWAKEUP by _umtx_unlock, it is possible a signal delivered to the thread will cause msleep returns EINTR, and the thread breaks out of loop, this causes umtx ownership is not transfered to the thread. Another is in _umtx_unlock itself, when the function sets the umtx to UMTX_UNOWNED state, a new thread can come in and lock the umtx, also the function tries to set contested bit flag, but it will fail. Although the function will wake a blocked thread, if that thread breaks out of loop by signal, no contested bit will be set.
2004-11-30 12:02:53 +00:00
};
- Remove the blocked pointer from the umtx structure. - Use a hash of umtx queues to queue blocked threads. We hash on pid and the virtual address of the umtx structure. This eliminates cases where we previously held a lock across a casuptr call. Reviwed by: jhb (quickly)
2003-06-03 05:24:46 +00:00
1. use per-chain mutex instead of global mutex to reduce lock collision. 2. Fix two race conditions. One is between _umtx_unlock and signal, also a thread was marked TDF_UMTXWAKEUP by _umtx_unlock, it is possible a signal delivered to the thread will cause msleep returns EINTR, and the thread breaks out of loop, this causes umtx ownership is not transfered to the thread. Another is in _umtx_unlock itself, when the function sets the umtx to UMTX_UNOWNED state, a new thread can come in and lock the umtx, also the function tries to set contested bit flag, but it will fail. Although the function will wake a blocked thread, if that thread breaks out of loop by signal, no contested bit will be set.
2004-11-30 12:02:53 +00:00
#define GOLDEN_RATIO_PRIME 2654404609U
#define UMTX_CHAINS 128
#define UMTX_SHIFTS (__WORD_BIT - 7)
- Remove the blocked pointer from the umtx structure. - Use a hash of umtx queues to queue blocked threads. We hash on pid and the virtual address of the umtx structure. This eliminates cases where we previously held a lock across a casuptr call. Reviwed by: jhb (quickly)
2003-06-03 05:24:46 +00:00
1. use per-chain mutex instead of global mutex to reduce lock collision. 2. Fix two race conditions. One is between _umtx_unlock and signal, also a thread was marked TDF_UMTXWAKEUP by _umtx_unlock, it is possible a signal delivered to the thread will cause msleep returns EINTR, and the thread breaks out of loop, this causes umtx ownership is not transfered to the thread. Another is in _umtx_unlock itself, when the function sets the umtx to UMTX_UNOWNED state, a new thread can come in and lock the umtx, also the function tries to set contested bit flag, but it will fail. Although the function will wake a blocked thread, if that thread breaks out of loop by signal, no contested bit will be set.
2004-11-30 12:02:53 +00:00
static struct umtxq_chain umtxq_chains[UMTX_CHAINS];
static MALLOC_DEFINE(M_UMTX, "umtx", "UMTX queue memory");
- Create a new lock, umtx_lock, for use instead of the proc lock for protecting the umtx queues. We can't use the proc lock because we need to hold the lock across calls to casuptr, which can fault. Approved by: re
2003-05-25 18:18:32 +00:00
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
static void umtxq_init_chains(void *);
static int umtxq_hash(struct umtx_key *key);
static struct mtx *umtxq_mtx(int chain);
static void umtxq_lock(struct umtx_key *key);
static void umtxq_unlock(struct umtx_key *key);
1. Fix race condition between umtx lock and unlock, heavy testing on SMP can explore the bug. 2. Let umtx_wake returns number of threads have been woken.
2004-12-24 11:30:55 +00:00
static void umtxq_busy(struct umtx_key *key);
static void umtxq_unbusy(struct umtx_key *key);
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
static void umtxq_insert(struct umtx_q *uq);
static void umtxq_remove(struct umtx_q *uq);
static int umtxq_sleep(struct thread *td, struct umtx_key *key,
int prio, const char *wmesg, int timo);
1. Fix race condition between umtx lock and unlock, heavy testing on SMP can explore the bug. 2. Let umtx_wake returns number of threads have been woken.
2004-12-24 11:30:55 +00:00
static int umtxq_count(struct umtx_key *key);
static int umtxq_signal(struct umtx_key *key, int nr_wakeup);
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
#ifdef UMTX_DYNAMIC_SHARED
static void fork_handler(void *arg, struct proc *p1, struct proc *p2,
int flags);
#endif
static int umtx_key_match(const struct umtx_key *k1, const struct umtx_key *k2);
static int umtx_key_get(struct thread *td, struct umtx *umtx,
struct umtx_key *key);
static void umtx_key_release(struct umtx_key *key);
SYSINIT(umtx, SI_SUB_EVENTHANDLER+1, SI_ORDER_MIDDLE, umtxq_init_chains, NULL);
1. use per-chain mutex instead of global mutex to reduce lock collision. 2. Fix two race conditions. One is between _umtx_unlock and signal, also a thread was marked TDF_UMTXWAKEUP by _umtx_unlock, it is possible a signal delivered to the thread will cause msleep returns EINTR, and the thread breaks out of loop, this causes umtx ownership is not transfered to the thread. Another is in _umtx_unlock itself, when the function sets the umtx to UMTX_UNOWNED state, a new thread can come in and lock the umtx, also the function tries to set contested bit flag, but it will fail. Although the function will wake a blocked thread, if that thread breaks out of loop by signal, no contested bit will be set.
2004-11-30 12:02:53 +00:00
static void
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
umtxq_init_chains(void *arg __unused)
1. use per-chain mutex instead of global mutex to reduce lock collision. 2. Fix two race conditions. One is between _umtx_unlock and signal, also a thread was marked TDF_UMTXWAKEUP by _umtx_unlock, it is possible a signal delivered to the thread will cause msleep returns EINTR, and the thread breaks out of loop, this causes umtx ownership is not transfered to the thread. Another is in _umtx_unlock itself, when the function sets the umtx to UMTX_UNOWNED state, a new thread can come in and lock the umtx, also the function tries to set contested bit flag, but it will fail. Although the function will wake a blocked thread, if that thread breaks out of loop by signal, no contested bit will be set.
2004-11-30 12:02:53 +00:00
{
int i;
for (i = 0; i < UMTX_CHAINS; ++i) {
mtx_init(&umtxq_chains[i].uc_lock, "umtxq_lock", NULL,
MTX_DEF | MTX_DUPOK);
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
LIST_INIT(&umtxq_chains[i].uc_queue);
1. Fix race condition between umtx lock and unlock, heavy testing on SMP can explore the bug. 2. Let umtx_wake returns number of threads have been woken.
2004-12-24 11:30:55 +00:00
umtxq_chains[i].uc_flags = 0;
1. use per-chain mutex instead of global mutex to reduce lock collision. 2. Fix two race conditions. One is between _umtx_unlock and signal, also a thread was marked TDF_UMTXWAKEUP by _umtx_unlock, it is possible a signal delivered to the thread will cause msleep returns EINTR, and the thread breaks out of loop, this causes umtx ownership is not transfered to the thread. Another is in _umtx_unlock itself, when the function sets the umtx to UMTX_UNOWNED state, a new thread can come in and lock the umtx, also the function tries to set contested bit flag, but it will fail. Although the function will wake a blocked thread, if that thread breaks out of loop by signal, no contested bit will be set.
2004-11-30 12:02:53 +00:00
}
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
#ifdef UMTX_DYNAMIC_SHARED
EVENTHANDLER_REGISTER(process_fork, fork_handler, 0, 10000);
#endif
1. use per-chain mutex instead of global mutex to reduce lock collision. 2. Fix two race conditions. One is between _umtx_unlock and signal, also a thread was marked TDF_UMTXWAKEUP by _umtx_unlock, it is possible a signal delivered to the thread will cause msleep returns EINTR, and the thread breaks out of loop, this causes umtx ownership is not transfered to the thread. Another is in _umtx_unlock itself, when the function sets the umtx to UMTX_UNOWNED state, a new thread can come in and lock the umtx, also the function tries to set contested bit flag, but it will fail. Although the function will wake a blocked thread, if that thread breaks out of loop by signal, no contested bit will be set.
2004-11-30 12:02:53 +00:00
}
static inline int
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
umtxq_hash(struct umtx_key *key)
1. use per-chain mutex instead of global mutex to reduce lock collision. 2. Fix two race conditions. One is between _umtx_unlock and signal, also a thread was marked TDF_UMTXWAKEUP by _umtx_unlock, it is possible a signal delivered to the thread will cause msleep returns EINTR, and the thread breaks out of loop, this causes umtx ownership is not transfered to the thread. Another is in _umtx_unlock itself, when the function sets the umtx to UMTX_UNOWNED state, a new thread can come in and lock the umtx, also the function tries to set contested bit flag, but it will fail. Although the function will wake a blocked thread, if that thread breaks out of loop by signal, no contested bit will be set.
2004-11-30 12:02:53 +00:00
{
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
unsigned n = (uintptr_t)key->info.both.ptr + key->info.both.word;
1. use per-chain mutex instead of global mutex to reduce lock collision. 2. Fix two race conditions. One is between _umtx_unlock and signal, also a thread was marked TDF_UMTXWAKEUP by _umtx_unlock, it is possible a signal delivered to the thread will cause msleep returns EINTR, and the thread breaks out of loop, this causes umtx ownership is not transfered to the thread. Another is in _umtx_unlock itself, when the function sets the umtx to UMTX_UNOWNED state, a new thread can come in and lock the umtx, also the function tries to set contested bit flag, but it will fail. Although the function will wake a blocked thread, if that thread breaks out of loop by signal, no contested bit will be set.
2004-11-30 12:02:53 +00:00
return (((n * GOLDEN_RATIO_PRIME) >> UMTX_SHIFTS) % UMTX_CHAINS);
}
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
static inline int
umtx_key_match(const struct umtx_key *k1, const struct umtx_key *k2)
{
return (k1->type == k2->type &&
k1->info.both.ptr == k2->info.both.ptr &&
k1->info.both.word == k2->info.both.word);
}
static inline struct mtx *
umtxq_mtx(int chain)
{
return (&umtxq_chains[chain].uc_lock);
}
1. Fix race condition between umtx lock and unlock, heavy testing on SMP can explore the bug. 2. Let umtx_wake returns number of threads have been woken.
2004-12-24 11:30:55 +00:00
static inline void
umtxq_busy(struct umtx_key *key)
{
int chain = umtxq_hash(key);
mtx_assert(umtxq_mtx(chain), MA_OWNED);
while (umtxq_chains[chain].uc_flags & UCF_BUSY) {
umtxq_chains[chain].uc_flags |= UCF_WANT;
msleep(&umtxq_chains[chain], umtxq_mtx(chain),
curthread->td_priority, "umtxq_busy", 0);
}
umtxq_chains[chain].uc_flags |= UCF_BUSY;
}
static inline void
umtxq_unbusy(struct umtx_key *key)
{
int chain = umtxq_hash(key);
mtx_assert(umtxq_mtx(chain), MA_OWNED);
Add umtxq_lock/unlock around umtx_signal, fix debug kernel compiling, let umtx_lock returns EINTR when it returns ERESTART, this lets userland have chance to back off mtx lock code when needed.
2004-12-24 11:59:20 +00:00
KASSERT(umtxq_chains[chain].uc_flags & UCF_BUSY, ("not busy"));
1. Fix race condition between umtx lock and unlock, heavy testing on SMP can explore the bug. 2. Let umtx_wake returns number of threads have been woken.
2004-12-24 11:30:55 +00:00
umtxq_chains[chain].uc_flags &= ~UCF_BUSY;
if (umtxq_chains[chain].uc_flags & UCF_WANT) {
umtxq_chains[chain].uc_flags &= ~UCF_WANT;
wakeup(&umtxq_chains[chain]);
}
}
1. use per-chain mutex instead of global mutex to reduce lock collision. 2. Fix two race conditions. One is between _umtx_unlock and signal, also a thread was marked TDF_UMTXWAKEUP by _umtx_unlock, it is possible a signal delivered to the thread will cause msleep returns EINTR, and the thread breaks out of loop, this causes umtx ownership is not transfered to the thread. Another is in _umtx_unlock itself, when the function sets the umtx to UMTX_UNOWNED state, a new thread can come in and lock the umtx, also the function tries to set contested bit flag, but it will fail. Although the function will wake a blocked thread, if that thread breaks out of loop by signal, no contested bit will be set.
2004-11-30 12:02:53 +00:00
static inline void
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
umtxq_lock(struct umtx_key *key)
1. use per-chain mutex instead of global mutex to reduce lock collision. 2. Fix two race conditions. One is between _umtx_unlock and signal, also a thread was marked TDF_UMTXWAKEUP by _umtx_unlock, it is possible a signal delivered to the thread will cause msleep returns EINTR, and the thread breaks out of loop, this causes umtx ownership is not transfered to the thread. Another is in _umtx_unlock itself, when the function sets the umtx to UMTX_UNOWNED state, a new thread can come in and lock the umtx, also the function tries to set contested bit flag, but it will fail. Although the function will wake a blocked thread, if that thread breaks out of loop by signal, no contested bit will be set.
2004-11-30 12:02:53 +00:00
{
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
int chain = umtxq_hash(key);
mtx_lock(umtxq_mtx(chain));
1. use per-chain mutex instead of global mutex to reduce lock collision. 2. Fix two race conditions. One is between _umtx_unlock and signal, also a thread was marked TDF_UMTXWAKEUP by _umtx_unlock, it is possible a signal delivered to the thread will cause msleep returns EINTR, and the thread breaks out of loop, this causes umtx ownership is not transfered to the thread. Another is in _umtx_unlock itself, when the function sets the umtx to UMTX_UNOWNED state, a new thread can come in and lock the umtx, also the function tries to set contested bit flag, but it will fail. Although the function will wake a blocked thread, if that thread breaks out of loop by signal, no contested bit will be set.
2004-11-30 12:02:53 +00:00
}
Forgot to inline umtxq_unlock.
2004-11-30 12:18:53 +00:00
static inline void
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
umtxq_unlock(struct umtx_key *key)
1. use per-chain mutex instead of global mutex to reduce lock collision. 2. Fix two race conditions. One is between _umtx_unlock and signal, also a thread was marked TDF_UMTXWAKEUP by _umtx_unlock, it is possible a signal delivered to the thread will cause msleep returns EINTR, and the thread breaks out of loop, this causes umtx ownership is not transfered to the thread. Another is in _umtx_unlock itself, when the function sets the umtx to UMTX_UNOWNED state, a new thread can come in and lock the umtx, also the function tries to set contested bit flag, but it will fail. Although the function will wake a blocked thread, if that thread breaks out of loop by signal, no contested bit will be set.
2004-11-30 12:02:53 +00:00
{
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
int chain = umtxq_hash(key);
mtx_unlock(umtxq_mtx(chain));
1. use per-chain mutex instead of global mutex to reduce lock collision. 2. Fix two race conditions. One is between _umtx_unlock and signal, also a thread was marked TDF_UMTXWAKEUP by _umtx_unlock, it is possible a signal delivered to the thread will cause msleep returns EINTR, and the thread breaks out of loop, this causes umtx ownership is not transfered to the thread. Another is in _umtx_unlock itself, when the function sets the umtx to UMTX_UNOWNED state, a new thread can come in and lock the umtx, also the function tries to set contested bit flag, but it will fail. Although the function will wake a blocked thread, if that thread breaks out of loop by signal, no contested bit will be set.
2004-11-30 12:02:53 +00:00
}
- Remove the blocked pointer from the umtx structure. - Use a hash of umtx queues to queue blocked threads. We hash on pid and the virtual address of the umtx structure. This eliminates cases where we previously held a lock across a casuptr call. Reviwed by: jhb (quickly)
2003-06-03 05:24:46 +00:00
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
/*
* Insert a thread onto the umtx queue.
*/
static inline void
umtxq_insert(struct umtx_q *uq)
- Remove the blocked pointer from the umtx structure. - Use a hash of umtx queues to queue blocked threads. We hash on pid and the virtual address of the umtx structure. This eliminates cases where we previously held a lock across a casuptr call. Reviwed by: jhb (quickly)
2003-06-03 05:24:46 +00:00
{
struct umtx_head *head;
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
int chain = umtxq_hash(&uq->uq_key);
1. Fix race condition between umtx lock and unlock, heavy testing on SMP can explore the bug. 2. Let umtx_wake returns number of threads have been woken.
2004-12-24 11:30:55 +00:00
mtx_assert(umtxq_mtx(chain), MA_OWNED);
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
head = &umtxq_chains[chain].uc_queue;
LIST_INSERT_HEAD(head, uq, uq_next);
uq->uq_thread->td_umtxq = uq;
mtx_lock_spin(&sched_lock);
uq->uq_thread->td_flags |= TDF_UMTXQ;
mtx_unlock_spin(&sched_lock);
}
/*
* Remove thread from the umtx queue.
*/
static inline void
umtxq_remove(struct umtx_q *uq)
{
1. Fix race condition between umtx lock and unlock, heavy testing on SMP can explore the bug. 2. Let umtx_wake returns number of threads have been woken.
2004-12-24 11:30:55 +00:00
mtx_assert(umtxq_mtx(umtxq_hash(&uq->uq_key)), MA_OWNED);
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
if (uq->uq_thread->td_flags & TDF_UMTXQ) {
LIST_REMOVE(uq, uq_next);
uq->uq_thread->td_umtxq = NULL;
/* turning off TDF_UMTXQ should be the last thing. */
mtx_lock_spin(&sched_lock);
uq->uq_thread->td_flags &= ~TDF_UMTXQ;
mtx_unlock_spin(&sched_lock);
}
}
static int
umtxq_count(struct umtx_key *key)
{
- Remove the blocked pointer from the umtx structure. - Use a hash of umtx queues to queue blocked threads. We hash on pid and the virtual address of the umtx structure. This eliminates cases where we previously held a lock across a casuptr call. Reviwed by: jhb (quickly)
2003-06-03 05:24:46 +00:00
struct umtx_q *uq;
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
struct umtx_head *head;
int chain, count = 0;
- Remove the blocked pointer from the umtx structure. - Use a hash of umtx queues to queue blocked threads. We hash on pid and the virtual address of the umtx structure. This eliminates cases where we previously held a lock across a casuptr call. Reviwed by: jhb (quickly)
2003-06-03 05:24:46 +00:00
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
chain = umtxq_hash(key);
1. Fix race condition between umtx lock and unlock, heavy testing on SMP can explore the bug. 2. Let umtx_wake returns number of threads have been woken.
2004-12-24 11:30:55 +00:00
mtx_assert(umtxq_mtx(chain), MA_OWNED);
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
head = &umtxq_chains[chain].uc_queue;
- Remove the blocked pointer from the umtx structure. - Use a hash of umtx queues to queue blocked threads. We hash on pid and the virtual address of the umtx structure. This eliminates cases where we previously held a lock across a casuptr call. Reviwed by: jhb (quickly)
2003-06-03 05:24:46 +00:00
LIST_FOREACH(uq, head, uq_next) {
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
if (umtx_key_match(&uq->uq_key, key)) {
if (++count > 1)
break;
}
- Remove the blocked pointer from the umtx structure. - Use a hash of umtx queues to queue blocked threads. We hash on pid and the virtual address of the umtx structure. This eliminates cases where we previously held a lock across a casuptr call. Reviwed by: jhb (quickly)
2003-06-03 05:24:46 +00:00
}
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
return (count);
- Remove the blocked pointer from the umtx structure. - Use a hash of umtx queues to queue blocked threads. We hash on pid and the virtual address of the umtx structure. This eliminates cases where we previously held a lock across a casuptr call. Reviwed by: jhb (quickly)
2003-06-03 05:24:46 +00:00
}
1. Fix race condition between umtx lock and unlock, heavy testing on SMP can explore the bug. 2. Let umtx_wake returns number of threads have been woken.
2004-12-24 11:30:55 +00:00
static int
umtxq_signal(struct umtx_key *key, int n_wake)
- Remove the blocked pointer from the umtx structure. - Use a hash of umtx queues to queue blocked threads. We hash on pid and the virtual address of the umtx structure. This eliminates cases where we previously held a lock across a casuptr call. Reviwed by: jhb (quickly)
2003-06-03 05:24:46 +00:00
{
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
struct umtx_q *uq, *next;
struct umtx_head *head;
1. Fix race condition between umtx lock and unlock, heavy testing on SMP can explore the bug. 2. Let umtx_wake returns number of threads have been woken.
2004-12-24 11:30:55 +00:00
struct thread *blocked = NULL;
int chain, ret;
- Remove the blocked pointer from the umtx structure. - Use a hash of umtx queues to queue blocked threads. We hash on pid and the virtual address of the umtx structure. This eliminates cases where we previously held a lock across a casuptr call. Reviwed by: jhb (quickly)
2003-06-03 05:24:46 +00:00
1. Fix race condition between umtx lock and unlock, heavy testing on SMP can explore the bug. 2. Let umtx_wake returns number of threads have been woken.
2004-12-24 11:30:55 +00:00
ret = 0;
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
chain = umtxq_hash(key);
1. Fix race condition between umtx lock and unlock, heavy testing on SMP can explore the bug. 2. Let umtx_wake returns number of threads have been woken.
2004-12-24 11:30:55 +00:00
mtx_assert(umtxq_mtx(chain), MA_OWNED);
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
head = &umtxq_chains[chain].uc_queue;
1. Fix race condition between umtx lock and unlock, heavy testing on SMP can explore the bug. 2. Let umtx_wake returns number of threads have been woken.
2004-12-24 11:30:55 +00:00
for (uq = LIST_FIRST(head); uq; uq = next) {
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
next = LIST_NEXT(uq, uq_next);
if (umtx_key_match(&uq->uq_key, key)) {
blocked = uq->uq_thread;
umtxq_remove(uq);
wakeup(blocked);
1. Fix race condition between umtx lock and unlock, heavy testing on SMP can explore the bug. 2. Let umtx_wake returns number of threads have been woken.
2004-12-24 11:30:55 +00:00
if (++ret >= n_wake)
break;
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
}
}
1. Fix race condition between umtx lock and unlock, heavy testing on SMP can explore the bug. 2. Let umtx_wake returns number of threads have been woken.
2004-12-24 11:30:55 +00:00
return (ret);
1. use per-chain mutex instead of global mutex to reduce lock collision. 2. Fix two race conditions. One is between _umtx_unlock and signal, also a thread was marked TDF_UMTXWAKEUP by _umtx_unlock, it is possible a signal delivered to the thread will cause msleep returns EINTR, and the thread breaks out of loop, this causes umtx ownership is not transfered to the thread. Another is in _umtx_unlock itself, when the function sets the umtx to UMTX_UNOWNED state, a new thread can come in and lock the umtx, also the function tries to set contested bit flag, but it will fail. Although the function will wake a blocked thread, if that thread breaks out of loop by signal, no contested bit will be set.
2004-11-30 12:02:53 +00:00
}
static inline int
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
umtxq_sleep(struct thread *td, struct umtx_key *key, int priority,
const char *wmesg, int timo)
1. use per-chain mutex instead of global mutex to reduce lock collision. 2. Fix two race conditions. One is between _umtx_unlock and signal, also a thread was marked TDF_UMTXWAKEUP by _umtx_unlock, it is possible a signal delivered to the thread will cause msleep returns EINTR, and the thread breaks out of loop, this causes umtx ownership is not transfered to the thread. Another is in _umtx_unlock itself, when the function sets the umtx to UMTX_UNOWNED state, a new thread can come in and lock the umtx, also the function tries to set contested bit flag, but it will fail. Although the function will wake a blocked thread, if that thread breaks out of loop by signal, no contested bit will be set.
2004-11-30 12:02:53 +00:00
{
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
int chain = umtxq_hash(key);
Return ETIMEDOUT when thread is timeouted since POSIX thread APIs expect ETIMEDOUT not EAGAIN, this simplifies userland code a bit.
2005-01-06 02:08:34 +00:00
int error = msleep(td, umtxq_mtx(chain), priority, wmesg, timo);
if (error == EWOULDBLOCK)
error = ETIMEDOUT;
return (error);
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
}
static int
umtx_key_get(struct thread *td, struct umtx *umtx, struct umtx_key *key)
{
#if defined(UMTX_DYNAMIC_SHARED) || defined(UMTX_STATIC_SHARED)
vm_map_t map;
vm_map_entry_t entry;
vm_pindex_t pindex;
vm_prot_t prot;
boolean_t wired;
map = &td->td_proc->p_vmspace->vm_map;
if (vm_map_lookup(&map, (vm_offset_t)umtx, VM_PROT_WRITE,
&entry, &key->info.shared.object, &pindex, &prot,
&wired) != KERN_SUCCESS) {
return EFAULT;
}
#endif
#if defined(UMTX_DYNAMIC_SHARED)
key->type = UMTX_SHARED;
key->info.shared.offset = entry->offset + entry->start -
(vm_offset_t)umtx;
/*
* Add object reference, if we don't do this, a buggy application
* deallocates the object, the object will be reused by other
* applications, then unlock will wake wrong thread.
*/
vm_object_reference(key->info.shared.object);
vm_map_lookup_done(map, entry);
#elif defined(UMTX_STATIC_SHARED)
if (VM_INHERIT_SHARE == entry->inheritance) {
key->type = UMTX_SHARED;
key->info.shared.offset = entry->offset + entry->start -
(vm_offset_t)umtx;
vm_object_reference(key->info.shared.object);
} else {
key->type = UMTX_PRIVATE;
key->info.private.umtx = umtx;
key->info.private.pid = td->td_proc->p_pid;
}
vm_map_lookup_done(map, entry);
#else
key->type = UMTX_PRIVATE;
key->info.private.umtx = umtx;
key->info.private.pid = td->td_proc->p_pid;
#endif
return (0);
}
static inline void
umtx_key_release(struct umtx_key *key)
{
if (key->type == UMTX_SHARED)
vm_object_deallocate(key->info.shared.object);
1. use per-chain mutex instead of global mutex to reduce lock collision. 2. Fix two race conditions. One is between _umtx_unlock and signal, also a thread was marked TDF_UMTXWAKEUP by _umtx_unlock, it is possible a signal delivered to the thread will cause msleep returns EINTR, and the thread breaks out of loop, this causes umtx ownership is not transfered to the thread. Another is in _umtx_unlock itself, when the function sets the umtx to UMTX_UNOWNED state, a new thread can come in and lock the umtx, also the function tries to set contested bit flag, but it will fail. Although the function will wake a blocked thread, if that thread breaks out of loop by signal, no contested bit will be set.
2004-11-30 12:02:53 +00:00
}
static inline int
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
umtxq_queue_me(struct thread *td, struct umtx *umtx, struct umtx_q *uq)
1. use per-chain mutex instead of global mutex to reduce lock collision. 2. Fix two race conditions. One is between _umtx_unlock and signal, also a thread was marked TDF_UMTXWAKEUP by _umtx_unlock, it is possible a signal delivered to the thread will cause msleep returns EINTR, and the thread breaks out of loop, this causes umtx ownership is not transfered to the thread. Another is in _umtx_unlock itself, when the function sets the umtx to UMTX_UNOWNED state, a new thread can come in and lock the umtx, also the function tries to set contested bit flag, but it will fail. Although the function will wake a blocked thread, if that thread breaks out of loop by signal, no contested bit will be set.
2004-11-30 12:02:53 +00:00
{
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
int error;
1. use per-chain mutex instead of global mutex to reduce lock collision. 2. Fix two race conditions. One is between _umtx_unlock and signal, also a thread was marked TDF_UMTXWAKEUP by _umtx_unlock, it is possible a signal delivered to the thread will cause msleep returns EINTR, and the thread breaks out of loop, this causes umtx ownership is not transfered to the thread. Another is in _umtx_unlock itself, when the function sets the umtx to UMTX_UNOWNED state, a new thread can come in and lock the umtx, also the function tries to set contested bit flag, but it will fail. Although the function will wake a blocked thread, if that thread breaks out of loop by signal, no contested bit will be set.
2004-11-30 12:02:53 +00:00
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
if ((error = umtx_key_get(td, umtx, &uq->uq_key)) != 0)
return (error);
uq->uq_addr = (vm_offset_t)umtx;
uq->uq_thread = td;
umtxq_lock(&uq->uq_key);
1. Fix race condition between umtx lock and unlock, heavy testing on SMP can explore the bug. 2. Let umtx_wake returns number of threads have been woken.
2004-12-24 11:30:55 +00:00
/* hmm, for condition variable, we don't need busy flag. */
umtxq_busy(&uq->uq_key);
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
umtxq_insert(uq);
1. Fix race condition between umtx lock and unlock, heavy testing on SMP can explore the bug. 2. Let umtx_wake returns number of threads have been woken.
2004-12-24 11:30:55 +00:00
umtxq_unbusy(&uq->uq_key);
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
umtxq_unlock(&uq->uq_key);
return (0);
1. use per-chain mutex instead of global mutex to reduce lock collision. 2. Fix two race conditions. One is between _umtx_unlock and signal, also a thread was marked TDF_UMTXWAKEUP by _umtx_unlock, it is possible a signal delivered to the thread will cause msleep returns EINTR, and the thread breaks out of loop, this causes umtx ownership is not transfered to the thread. Another is in _umtx_unlock itself, when the function sets the umtx to UMTX_UNOWNED state, a new thread can come in and lock the umtx, also the function tries to set contested bit flag, but it will fail. Although the function will wake a blocked thread, if that thread breaks out of loop by signal, no contested bit will be set.
2004-11-30 12:02:53 +00:00
}
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
#if defined(UMTX_DYNAMIC_SHARED)
1. use per-chain mutex instead of global mutex to reduce lock collision. 2. Fix two race conditions. One is between _umtx_unlock and signal, also a thread was marked TDF_UMTXWAKEUP by _umtx_unlock, it is possible a signal delivered to the thread will cause msleep returns EINTR, and the thread breaks out of loop, this causes umtx ownership is not transfered to the thread. Another is in _umtx_unlock itself, when the function sets the umtx to UMTX_UNOWNED state, a new thread can come in and lock the umtx, also the function tries to set contested bit flag, but it will fail. Although the function will wake a blocked thread, if that thread breaks out of loop by signal, no contested bit will be set.
2004-11-30 12:02:53 +00:00
static void
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
fork_handler(void *arg, struct proc *p1, struct proc *p2, int flags)
1. use per-chain mutex instead of global mutex to reduce lock collision. 2. Fix two race conditions. One is between _umtx_unlock and signal, also a thread was marked TDF_UMTXWAKEUP by _umtx_unlock, it is possible a signal delivered to the thread will cause msleep returns EINTR, and the thread breaks out of loop, this causes umtx ownership is not transfered to the thread. Another is in _umtx_unlock itself, when the function sets the umtx to UMTX_UNOWNED state, a new thread can come in and lock the umtx, also the function tries to set contested bit flag, but it will fail. Although the function will wake a blocked thread, if that thread breaks out of loop by signal, no contested bit will be set.
2004-11-30 12:02:53 +00:00
{
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
vm_map_t map;
vm_map_entry_t entry;
vm_object_t object;
vm_pindex_t pindex;
vm_prot_t prot;
boolean_t wired;
struct umtx_key key;
LIST_HEAD(, umtx_q) workq;
1. use per-chain mutex instead of global mutex to reduce lock collision. 2. Fix two race conditions. One is between _umtx_unlock and signal, also a thread was marked TDF_UMTXWAKEUP by _umtx_unlock, it is possible a signal delivered to the thread will cause msleep returns EINTR, and the thread breaks out of loop, this causes umtx ownership is not transfered to the thread. Another is in _umtx_unlock itself, when the function sets the umtx to UMTX_UNOWNED state, a new thread can come in and lock the umtx, also the function tries to set contested bit flag, but it will fail. Although the function will wake a blocked thread, if that thread breaks out of loop by signal, no contested bit will be set.
2004-11-30 12:02:53 +00:00
struct umtx_q *uq;
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
struct thread *td;
int onq;
LIST_INIT(&workq);
/* Collect threads waiting on umtxq */
PROC_LOCK(p1);
FOREACH_THREAD_IN_PROC(p1, td) {
if (td->td_flags & TDF_UMTXQ) {
uq = td->td_umtxq;
if (uq)
LIST_INSERT_HEAD(&workq, uq, uq_rqnext);
}
}
PROC_UNLOCK(p1);
1. use per-chain mutex instead of global mutex to reduce lock collision. 2. Fix two race conditions. One is between _umtx_unlock and signal, also a thread was marked TDF_UMTXWAKEUP by _umtx_unlock, it is possible a signal delivered to the thread will cause msleep returns EINTR, and the thread breaks out of loop, this causes umtx ownership is not transfered to the thread. Another is in _umtx_unlock itself, when the function sets the umtx to UMTX_UNOWNED state, a new thread can come in and lock the umtx, also the function tries to set contested bit flag, but it will fail. Although the function will wake a blocked thread, if that thread breaks out of loop by signal, no contested bit will be set.
2004-11-30 12:02:53 +00:00
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
LIST_FOREACH(uq, &workq, uq_rqnext) {
map = &p1->p_vmspace->vm_map;
if (vm_map_lookup(&map, uq->uq_addr, VM_PROT_WRITE,
&entry, &object, &pindex, &prot, &wired) != KERN_SUCCESS) {
continue;
}
key.type = UMTX_SHARED;
key.info.shared.object = object;
key.info.shared.offset = entry->offset + entry->start -
uq->uq_addr;
if (umtx_key_match(&key, &uq->uq_key)) {
vm_map_lookup_done(map, entry);
continue;
1. use per-chain mutex instead of global mutex to reduce lock collision. 2. Fix two race conditions. One is between _umtx_unlock and signal, also a thread was marked TDF_UMTXWAKEUP by _umtx_unlock, it is possible a signal delivered to the thread will cause msleep returns EINTR, and the thread breaks out of loop, this causes umtx ownership is not transfered to the thread. Another is in _umtx_unlock itself, when the function sets the umtx to UMTX_UNOWNED state, a new thread can come in and lock the umtx, also the function tries to set contested bit flag, but it will fail. Although the function will wake a blocked thread, if that thread breaks out of loop by signal, no contested bit will be set.
2004-11-30 12:02:53 +00:00
}
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
umtxq_lock(&uq->uq_key);
1. Fix race condition between umtx lock and unlock, heavy testing on SMP can explore the bug. 2. Let umtx_wake returns number of threads have been woken.
2004-12-24 11:30:55 +00:00
umtxq_busy(&uq->uq_key);
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
if (uq->uq_thread->td_flags & TDF_UMTXQ) {
umtxq_remove(uq);
onq = 1;
} else
onq = 0;
1. Fix race condition between umtx lock and unlock, heavy testing on SMP can explore the bug. 2. Let umtx_wake returns number of threads have been woken.
2004-12-24 11:30:55 +00:00
umtxq_unbusy(&uq->uq_key);
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
umtxq_unlock(&uq->uq_key);
if (onq) {
vm_object_deallocate(uq->uq_key.info.shared.object);
uq->uq_key = key;
umtxq_lock(&uq->uq_key);
1. Fix race condition between umtx lock and unlock, heavy testing on SMP can explore the bug. 2. Let umtx_wake returns number of threads have been woken.
2004-12-24 11:30:55 +00:00
umtxq_busy(&uq->uq_key);
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
umtxq_insert(uq);
1. Fix race condition between umtx lock and unlock, heavy testing on SMP can explore the bug. 2. Let umtx_wake returns number of threads have been woken.
2004-12-24 11:30:55 +00:00
umtxq_unbusy(&uq->uq_key);
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
umtxq_unlock(&uq->uq_key);
vm_object_reference(uq->uq_key.info.shared.object);
}
vm_map_lookup_done(map, entry);
- Remove the blocked pointer from the umtx structure. - Use a hash of umtx queues to queue blocked threads. We hash on pid and the virtual address of the umtx structure. This eliminates cases where we previously held a lock across a casuptr call. Reviwed by: jhb (quickly)
2003-06-03 05:24:46 +00:00
}
}
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
#endif
- Create a new lock, umtx_lock, for use instead of the proc lock for protecting the umtx queues. We can't use the proc lock because we need to hold the lock across calls to casuptr, which can fault. Approved by: re
2003-05-25 18:18:32 +00:00
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
static int
_do_lock(struct thread *td, struct umtx *umtx, long id, int timo)
- Add an api for doing smp safe locks in userland. - umtx_lock() is defined as an inline in umtx.h. It tries to do an uncontested acquire of a lock which falls back to the _umtx_lock() system-call if that fails. - umtx_unlock() is also an inline which falls back to _umtx_unlock() if the uncontested unlock fails. - Locks are keyed off of the thr_id_t of the currently running thread which is currently just the pointer to the 'struct thread' in kernel. - _umtx_lock() uses the proc pointer to synchronize access to blocked thread queues which are stored in the first blocked thread.
2003-04-01 01:10:42 +00:00
{
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
struct umtx_q uq;
- Add an api for doing smp safe locks in userland. - umtx_lock() is defined as an inline in umtx.h. It tries to do an uncontested acquire of a lock which falls back to the _umtx_lock() system-call if that fails. - umtx_unlock() is also an inline which falls back to _umtx_unlock() if the uncontested unlock fails. - Locks are keyed off of the thr_id_t of the currently running thread which is currently just the pointer to the 'struct thread' in kernel. - _umtx_lock() uses the proc pointer to synchronize access to blocked thread queues which are stored in the first blocked thread.
2003-04-01 01:10:42 +00:00
intptr_t owner;
- Make casuptr return the old value of the location we're trying to update, and change the umtx code to expect this. Reviewed by: jeff
2003-04-02 08:02:27 +00:00
intptr_t old;
1. use per-chain mutex instead of global mutex to reduce lock collision. 2. Fix two race conditions. One is between _umtx_unlock and signal, also a thread was marked TDF_UMTXWAKEUP by _umtx_unlock, it is possible a signal delivered to the thread will cause msleep returns EINTR, and the thread breaks out of loop, this causes umtx ownership is not transfered to the thread. Another is in _umtx_unlock itself, when the function sets the umtx to UMTX_UNOWNED state, a new thread can come in and lock the umtx, also the function tries to set contested bit flag, but it will fail. Although the function will wake a blocked thread, if that thread breaks out of loop by signal, no contested bit will be set.
2004-11-30 12:02:53 +00:00
int error = 0;
- Add an api for doing smp safe locks in userland. - umtx_lock() is defined as an inline in umtx.h. It tries to do an uncontested acquire of a lock which falls back to the _umtx_lock() system-call if that fails. - umtx_unlock() is also an inline which falls back to _umtx_unlock() if the uncontested unlock fails. - Locks are keyed off of the thr_id_t of the currently running thread which is currently just the pointer to the 'struct thread' in kernel. - _umtx_lock() uses the proc pointer to synchronize access to blocked thread queues which are stored in the first blocked thread.
2003-04-01 01:10:42 +00:00
/*
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
* Care must be exercised when dealing with umtx structure. It
- Add an api for doing smp safe locks in userland. - umtx_lock() is defined as an inline in umtx.h. It tries to do an uncontested acquire of a lock which falls back to the _umtx_lock() system-call if that fails. - umtx_unlock() is also an inline which falls back to _umtx_unlock() if the uncontested unlock fails. - Locks are keyed off of the thr_id_t of the currently running thread which is currently just the pointer to the 'struct thread' in kernel. - _umtx_lock() uses the proc pointer to synchronize access to blocked thread queues which are stored in the first blocked thread.
2003-04-01 01:10:42 +00:00
* can fault on any access.
*/
for (;;) {
/*
* Try the uncontested case. This should be done in userland.
*/
owner = casuptr((intptr_t *)&umtx->u_owner,
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
UMTX_UNOWNED, id);
- Add an api for doing smp safe locks in userland. - umtx_lock() is defined as an inline in umtx.h. It tries to do an uncontested acquire of a lock which falls back to the _umtx_lock() system-call if that fails. - umtx_unlock() is also an inline which falls back to _umtx_unlock() if the uncontested unlock fails. - Locks are keyed off of the thr_id_t of the currently running thread which is currently just the pointer to the 'struct thread' in kernel. - _umtx_lock() uses the proc pointer to synchronize access to blocked thread queues which are stored in the first blocked thread.
2003-04-01 01:10:42 +00:00
/* The acquire succeeded. */
- Remove the blocked pointer from the umtx structure. - Use a hash of umtx queues to queue blocked threads. We hash on pid and the virtual address of the umtx structure. This eliminates cases where we previously held a lock across a casuptr call. Reviwed by: jhb (quickly)
2003-06-03 05:24:46 +00:00
if (owner == UMTX_UNOWNED)
return (0);
- Add an api for doing smp safe locks in userland. - umtx_lock() is defined as an inline in umtx.h. It tries to do an uncontested acquire of a lock which falls back to the _umtx_lock() system-call if that fails. - umtx_unlock() is also an inline which falls back to _umtx_unlock() if the uncontested unlock fails. - Locks are keyed off of the thr_id_t of the currently running thread which is currently just the pointer to the 'struct thread' in kernel. - _umtx_lock() uses the proc pointer to synchronize access to blocked thread queues which are stored in the first blocked thread.
2003-04-01 01:10:42 +00:00
1. use per-chain mutex instead of global mutex to reduce lock collision. 2. Fix two race conditions. One is between _umtx_unlock and signal, also a thread was marked TDF_UMTXWAKEUP by _umtx_unlock, it is possible a signal delivered to the thread will cause msleep returns EINTR, and the thread breaks out of loop, this causes umtx ownership is not transfered to the thread. Another is in _umtx_unlock itself, when the function sets the umtx to UMTX_UNOWNED state, a new thread can come in and lock the umtx, also the function tries to set contested bit flag, but it will fail. Although the function will wake a blocked thread, if that thread breaks out of loop by signal, no contested bit will be set.
2004-11-30 12:02:53 +00:00
/* The address was invalid. */
if (owner == -1)
return (EFAULT);
- Remove the blocked pointer from the umtx structure. - Use a hash of umtx queues to queue blocked threads. We hash on pid and the virtual address of the umtx structure. This eliminates cases where we previously held a lock across a casuptr call. Reviwed by: jhb (quickly)
2003-06-03 05:24:46 +00:00
/* If no one owns it but it is contested try to acquire it. */
if (owner == UMTX_CONTESTED) {
owner = casuptr((intptr_t *)&umtx->u_owner,
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
UMTX_CONTESTED, id | UMTX_CONTESTED);
- Remove the blocked pointer from the umtx structure. - Use a hash of umtx queues to queue blocked threads. We hash on pid and the virtual address of the umtx structure. This eliminates cases where we previously held a lock across a casuptr call. Reviwed by: jhb (quickly)
2003-06-03 05:24:46 +00:00
1. use per-chain mutex instead of global mutex to reduce lock collision. 2. Fix two race conditions. One is between _umtx_unlock and signal, also a thread was marked TDF_UMTXWAKEUP by _umtx_unlock, it is possible a signal delivered to the thread will cause msleep returns EINTR, and the thread breaks out of loop, this causes umtx ownership is not transfered to the thread. Another is in _umtx_unlock itself, when the function sets the umtx to UMTX_UNOWNED state, a new thread can come in and lock the umtx, also the function tries to set contested bit flag, but it will fail. Although the function will wake a blocked thread, if that thread breaks out of loop by signal, no contested bit will be set.
2004-11-30 12:02:53 +00:00
if (owner == UMTX_CONTESTED)
return (0);
- Remove the blocked pointer from the umtx structure. - Use a hash of umtx queues to queue blocked threads. We hash on pid and the virtual address of the umtx structure. This eliminates cases where we previously held a lock across a casuptr call. Reviwed by: jhb (quickly)
2003-06-03 05:24:46 +00:00
/* The address was invalid. */
if (owner == -1)
return (EFAULT);
/* If this failed the lock has changed, restart. */
continue;
- Add an api for doing smp safe locks in userland. - umtx_lock() is defined as an inline in umtx.h. It tries to do an uncontested acquire of a lock which falls back to the _umtx_lock() system-call if that fails. - umtx_unlock() is also an inline which falls back to _umtx_unlock() if the uncontested unlock fails. - Locks are keyed off of the thr_id_t of the currently running thread which is currently just the pointer to the 'struct thread' in kernel. - _umtx_lock() uses the proc pointer to synchronize access to blocked thread queues which are stored in the first blocked thread.
2003-04-01 01:10:42 +00:00
}
1. use per-chain mutex instead of global mutex to reduce lock collision. 2. Fix two race conditions. One is between _umtx_unlock and signal, also a thread was marked TDF_UMTXWAKEUP by _umtx_unlock, it is possible a signal delivered to the thread will cause msleep returns EINTR, and the thread breaks out of loop, this causes umtx ownership is not transfered to the thread. Another is in _umtx_unlock itself, when the function sets the umtx to UMTX_UNOWNED state, a new thread can come in and lock the umtx, also the function tries to set contested bit flag, but it will fail. Although the function will wake a blocked thread, if that thread breaks out of loop by signal, no contested bit will be set.
2004-11-30 12:02:53 +00:00
/*
* If we caught a signal, we have retried and now
* exit immediately.
*/
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
if (error || (error = umtxq_queue_me(td, umtx, &uq)) != 0)
1. use per-chain mutex instead of global mutex to reduce lock collision. 2. Fix two race conditions. One is between _umtx_unlock and signal, also a thread was marked TDF_UMTXWAKEUP by _umtx_unlock, it is possible a signal delivered to the thread will cause msleep returns EINTR, and the thread breaks out of loop, this causes umtx ownership is not transfered to the thread. Another is in _umtx_unlock itself, when the function sets the umtx to UMTX_UNOWNED state, a new thread can come in and lock the umtx, also the function tries to set contested bit flag, but it will fail. Although the function will wake a blocked thread, if that thread breaks out of loop by signal, no contested bit will be set.
2004-11-30 12:02:53 +00:00
return (error);
- Remove the blocked pointer from the umtx structure. - Use a hash of umtx queues to queue blocked threads. We hash on pid and the virtual address of the umtx structure. This eliminates cases where we previously held a lock across a casuptr call. Reviwed by: jhb (quickly)
2003-06-03 05:24:46 +00:00
- Add an api for doing smp safe locks in userland. - umtx_lock() is defined as an inline in umtx.h. It tries to do an uncontested acquire of a lock which falls back to the _umtx_lock() system-call if that fails. - umtx_unlock() is also an inline which falls back to _umtx_unlock() if the uncontested unlock fails. - Locks are keyed off of the thr_id_t of the currently running thread which is currently just the pointer to the 'struct thread' in kernel. - _umtx_lock() uses the proc pointer to synchronize access to blocked thread queues which are stored in the first blocked thread.
2003-04-01 01:10:42 +00:00
/*
* Set the contested bit so that a release in user space
* knows to use the system call for unlock. If this fails
* either some one else has acquired the lock or it has been
* released.
*/
- Make casuptr return the old value of the location we're trying to update, and change the umtx code to expect this. Reviewed by: jeff
2003-04-02 08:02:27 +00:00
old = casuptr((intptr_t *)&umtx->u_owner, owner,
owner | UMTX_CONTESTED);
- Add an api for doing smp safe locks in userland. - umtx_lock() is defined as an inline in umtx.h. It tries to do an uncontested acquire of a lock which falls back to the _umtx_lock() system-call if that fails. - umtx_unlock() is also an inline which falls back to _umtx_unlock() if the uncontested unlock fails. - Locks are keyed off of the thr_id_t of the currently running thread which is currently just the pointer to the 'struct thread' in kernel. - _umtx_lock() uses the proc pointer to synchronize access to blocked thread queues which are stored in the first blocked thread.
2003-04-01 01:10:42 +00:00
/* The address was invalid. */
- Make casuptr return the old value of the location we're trying to update, and change the umtx code to expect this. Reviewed by: jeff
2003-04-02 08:02:27 +00:00
if (old == -1) {
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
umtxq_lock(&uq.uq_key);
1. Fix race condition between umtx lock and unlock, heavy testing on SMP can explore the bug. 2. Let umtx_wake returns number of threads have been woken.
2004-12-24 11:30:55 +00:00
umtxq_busy(&uq.uq_key);
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
umtxq_remove(&uq);
1. Fix race condition between umtx lock and unlock, heavy testing on SMP can explore the bug. 2. Let umtx_wake returns number of threads have been woken.
2004-12-24 11:30:55 +00:00
umtxq_unbusy(&uq.uq_key);
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
umtxq_unlock(&uq.uq_key);
umtx_key_release(&uq.uq_key);
- Remove the blocked pointer from the umtx structure. - Use a hash of umtx queues to queue blocked threads. We hash on pid and the virtual address of the umtx structure. This eliminates cases where we previously held a lock across a casuptr call. Reviwed by: jhb (quickly)
2003-06-03 05:24:46 +00:00
return (EFAULT);
- Add an api for doing smp safe locks in userland. - umtx_lock() is defined as an inline in umtx.h. It tries to do an uncontested acquire of a lock which falls back to the _umtx_lock() system-call if that fails. - umtx_unlock() is also an inline which falls back to _umtx_unlock() if the uncontested unlock fails. - Locks are keyed off of the thr_id_t of the currently running thread which is currently just the pointer to the 'struct thread' in kernel. - _umtx_lock() uses the proc pointer to synchronize access to blocked thread queues which are stored in the first blocked thread.
2003-04-01 01:10:42 +00:00
}
/*
- Remove the blocked pointer from the umtx structure. - Use a hash of umtx queues to queue blocked threads. We hash on pid and the virtual address of the umtx structure. This eliminates cases where we previously held a lock across a casuptr call. Reviwed by: jhb (quickly)
2003-06-03 05:24:46 +00:00
* We set the contested bit, sleep. Otherwise the lock changed
Fix umtx locking, for libthr, in the kernel. 1. There was a race condition between a thread unlocking a umtx and the thread contesting it. If the unlocking thread won the race it may try to wakeup a thread that was not yet in msleep(). The contesting thread would then go to sleep to await a wakeup that would never come. It's not possible to close the race by using a lock because calls to casuptr() may have to fault a page in from swap. Instead, the race was closed by introducing a flag that the unlocking thread will set when waking up a thread. The contesting thread will check for this flag before going to sleep. For now the flag is kept in td_flags, but it may be better to use some other member or create a new one because of the possible performance/contention issues of having to own sched_lock. Thanks to jhb for pointing me in the right direction on this one. 2. Once a umtx was contested all future locks and unlocks were happening in the kernel, regardless of whether it was contested or not. To prevent this from happening, when a thread locks a umtx it checks the queue for that umtx and unsets the contested bit if there are no other threads waiting on it. Again, this is slightly more complicated than it needs to be because we can't hold a lock across casuptr(). So, the thread has to check the queue again after unseting the bit, and reset the contested bit if it finds that another thread has put itself on the queue in the mean time. 3. Remove the if... block for unlocking an uncontested umtx, and replace it with a KASSERT. The _only_ time a thread should be unlocking a umtx in the kernel is if it is contested.
2003-07-17 11:06:40 +00:00
* and we need to retry or we lost a race to the thread
* unlocking the umtx.
- Add an api for doing smp safe locks in userland. - umtx_lock() is defined as an inline in umtx.h. It tries to do an uncontested acquire of a lock which falls back to the _umtx_lock() system-call if that fails. - umtx_unlock() is also an inline which falls back to _umtx_unlock() if the uncontested unlock fails. - Locks are keyed off of the thr_id_t of the currently running thread which is currently just the pointer to the 'struct thread' in kernel. - _umtx_lock() uses the proc pointer to synchronize access to blocked thread queues which are stored in the first blocked thread.
2003-04-01 01:10:42 +00:00
*/
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
umtxq_lock(&uq.uq_key);
if (old == owner && (td->td_flags & TDF_UMTXQ)) {
error = umtxq_sleep(td, &uq.uq_key,
1. Fix race condition between umtx lock and unlock, heavy testing on SMP can explore the bug. 2. Let umtx_wake returns number of threads have been woken.
2004-12-24 11:30:55 +00:00
td->td_priority | PCATCH,
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
"umtx", timo);
1. use per-chain mutex instead of global mutex to reduce lock collision. 2. Fix two race conditions. One is between _umtx_unlock and signal, also a thread was marked TDF_UMTXWAKEUP by _umtx_unlock, it is possible a signal delivered to the thread will cause msleep returns EINTR, and the thread breaks out of loop, this causes umtx ownership is not transfered to the thread. Another is in _umtx_unlock itself, when the function sets the umtx to UMTX_UNOWNED state, a new thread can come in and lock the umtx, also the function tries to set contested bit flag, but it will fail. Although the function will wake a blocked thread, if that thread breaks out of loop by signal, no contested bit will be set.
2004-11-30 12:02:53 +00:00
}
1. Fix race condition between umtx lock and unlock, heavy testing on SMP can explore the bug. 2. Let umtx_wake returns number of threads have been woken.
2004-12-24 11:30:55 +00:00
umtxq_busy(&uq.uq_key);
umtxq_remove(&uq);
umtxq_unbusy(&uq.uq_key);
umtxq_unlock(&uq.uq_key);
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
umtx_key_release(&uq.uq_key);
- Add an api for doing smp safe locks in userland. - umtx_lock() is defined as an inline in umtx.h. It tries to do an uncontested acquire of a lock which falls back to the _umtx_lock() system-call if that fails. - umtx_unlock() is also an inline which falls back to _umtx_unlock() if the uncontested unlock fails. - Locks are keyed off of the thr_id_t of the currently running thread which is currently just the pointer to the 'struct thread' in kernel. - _umtx_lock() uses the proc pointer to synchronize access to blocked thread queues which are stored in the first blocked thread.
2003-04-01 01:10:42 +00:00
}
Move the decision on whether to unset the contested bit or not from lock to unlock time. Suggested by: jhb
2003-07-18 17:58:37 +00:00
return (0);
- Add an api for doing smp safe locks in userland. - umtx_lock() is defined as an inline in umtx.h. It tries to do an uncontested acquire of a lock which falls back to the _umtx_lock() system-call if that fails. - umtx_unlock() is also an inline which falls back to _umtx_unlock() if the uncontested unlock fails. - Locks are keyed off of the thr_id_t of the currently running thread which is currently just the pointer to the 'struct thread' in kernel. - _umtx_lock() uses the proc pointer to synchronize access to blocked thread queues which are stored in the first blocked thread.
2003-04-01 01:10:42 +00:00
}
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
static int
do_lock(struct thread *td, struct umtx *umtx, long id,
struct timespec *abstime)
{
struct timespec ts1, ts2;
struct timeval tv;
int timo, error;
if (abstime == NULL) {
error = _do_lock(td, umtx, id, 0);
} else {
for (;;) {
ts1 = *abstime;
getnanotime(&ts2);
timespecsub(&ts1, &ts2);
TIMESPEC_TO_TIMEVAL(&tv, &ts1);
if (tv.tv_sec < 0) {
Return ETIMEDOUT when thread is timeouted since POSIX thread APIs expect ETIMEDOUT not EAGAIN, this simplifies userland code a bit.
2005-01-06 02:08:34 +00:00
error = ETIMEDOUT;
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
break;
}
timo = tvtohz(&tv);
error = _do_lock(td, umtx, id, timo);
Return ETIMEDOUT when thread is timeouted since POSIX thread APIs expect ETIMEDOUT not EAGAIN, this simplifies userland code a bit.
2005-01-06 02:08:34 +00:00
if (error != ETIMEDOUT)
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
break;
}
}
Add umtxq_lock/unlock around umtx_signal, fix debug kernel compiling, let umtx_lock returns EINTR when it returns ERESTART, this lets userland have chance to back off mtx lock code when needed.
2004-12-24 11:59:20 +00:00
/*
* This lets userland back off critical region if needed.
*/
if (error == ERESTART)
error = EINTR;
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
return (error);
}
static int
do_unlock(struct thread *td, struct umtx *umtx, long id)
- Add an api for doing smp safe locks in userland. - umtx_lock() is defined as an inline in umtx.h. It tries to do an uncontested acquire of a lock which falls back to the _umtx_lock() system-call if that fails. - umtx_unlock() is also an inline which falls back to _umtx_unlock() if the uncontested unlock fails. - Locks are keyed off of the thr_id_t of the currently running thread which is currently just the pointer to the 'struct thread' in kernel. - _umtx_lock() uses the proc pointer to synchronize access to blocked thread queues which are stored in the first blocked thread.
2003-04-01 01:10:42 +00:00
{
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
struct umtx_key key;
- Add an api for doing smp safe locks in userland. - umtx_lock() is defined as an inline in umtx.h. It tries to do an uncontested acquire of a lock which falls back to the _umtx_lock() system-call if that fails. - umtx_unlock() is also an inline which falls back to _umtx_unlock() if the uncontested unlock fails. - Locks are keyed off of the thr_id_t of the currently running thread which is currently just the pointer to the 'struct thread' in kernel. - _umtx_lock() uses the proc pointer to synchronize access to blocked thread queues which are stored in the first blocked thread.
2003-04-01 01:10:42 +00:00
intptr_t owner;
- Make casuptr return the old value of the location we're trying to update, and change the umtx code to expect this. Reviewed by: jeff
2003-04-02 08:02:27 +00:00
intptr_t old;
1. Fix race condition between umtx lock and unlock, heavy testing on SMP can explore the bug. 2. Let umtx_wake returns number of threads have been woken.
2004-12-24 11:30:55 +00:00
int error;
int count;
- Add an api for doing smp safe locks in userland. - umtx_lock() is defined as an inline in umtx.h. It tries to do an uncontested acquire of a lock which falls back to the _umtx_lock() system-call if that fails. - umtx_unlock() is also an inline which falls back to _umtx_unlock() if the uncontested unlock fails. - Locks are keyed off of the thr_id_t of the currently running thread which is currently just the pointer to the 'struct thread' in kernel. - _umtx_lock() uses the proc pointer to synchronize access to blocked thread queues which are stored in the first blocked thread.
2003-04-01 01:10:42 +00:00
/*
* Make sure we own this mtx.
*
* XXX Need a {fu,su}ptr this is not correct on arch where
* sizeof(intptr_t) != sizeof(long).
*/
- Remove the blocked pointer from the umtx structure. - Use a hash of umtx queues to queue blocked threads. We hash on pid and the virtual address of the umtx structure. This eliminates cases where we previously held a lock across a casuptr call. Reviwed by: jhb (quickly)
2003-06-03 05:24:46 +00:00
if ((owner = fuword(&umtx->u_owner)) == -1)
return (EFAULT);
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
if ((owner & ~UMTX_CONTESTED) != id)
- Remove the blocked pointer from the umtx structure. - Use a hash of umtx queues to queue blocked threads. We hash on pid and the virtual address of the umtx structure. This eliminates cases where we previously held a lock across a casuptr call. Reviwed by: jhb (quickly)
2003-06-03 05:24:46 +00:00
return (EPERM);
- Add an api for doing smp safe locks in userland. - umtx_lock() is defined as an inline in umtx.h. It tries to do an uncontested acquire of a lock which falls back to the _umtx_lock() system-call if that fails. - umtx_unlock() is also an inline which falls back to _umtx_unlock() if the uncontested unlock fails. - Locks are keyed off of the thr_id_t of the currently running thread which is currently just the pointer to the 'struct thread' in kernel. - _umtx_lock() uses the proc pointer to synchronize access to blocked thread queues which are stored in the first blocked thread.
2003-04-01 01:10:42 +00:00
Fix umtx locking, for libthr, in the kernel. 1. There was a race condition between a thread unlocking a umtx and the thread contesting it. If the unlocking thread won the race it may try to wakeup a thread that was not yet in msleep(). The contesting thread would then go to sleep to await a wakeup that would never come. It's not possible to close the race by using a lock because calls to casuptr() may have to fault a page in from swap. Instead, the race was closed by introducing a flag that the unlocking thread will set when waking up a thread. The contesting thread will check for this flag before going to sleep. For now the flag is kept in td_flags, but it may be better to use some other member or create a new one because of the possible performance/contention issues of having to own sched_lock. Thanks to jhb for pointing me in the right direction on this one. 2. Once a umtx was contested all future locks and unlocks were happening in the kernel, regardless of whether it was contested or not. To prevent this from happening, when a thread locks a umtx it checks the queue for that umtx and unsets the contested bit if there are no other threads waiting on it. Again, this is slightly more complicated than it needs to be because we can't hold a lock across casuptr(). So, the thread has to check the queue again after unseting the bit, and reset the contested bit if it finds that another thread has put itself on the queue in the mean time. 3. Remove the if... block for unlocking an uncontested umtx, and replace it with a KASSERT. The _only_ time a thread should be unlocking a umtx in the kernel is if it is contested.
2003-07-17 11:06:40 +00:00
/* We should only ever be in here for contested locks */
Return EINVAL if the contested bit is not set on the umtx passed to _umtx_unlock() instead of firing a KASSERT.
2003-09-07 11:14:52 +00:00
if ((owner & UMTX_CONTESTED) == 0)
return (EINVAL);
- Add an api for doing smp safe locks in userland. - umtx_lock() is defined as an inline in umtx.h. It tries to do an uncontested acquire of a lock which falls back to the _umtx_lock() system-call if that fails. - umtx_unlock() is also an inline which falls back to _umtx_unlock() if the uncontested unlock fails. - Locks are keyed off of the thr_id_t of the currently running thread which is currently just the pointer to the 'struct thread' in kernel. - _umtx_lock() uses the proc pointer to synchronize access to blocked thread queues which are stored in the first blocked thread.
2003-04-01 01:10:42 +00:00
1. Fix race condition between umtx lock and unlock, heavy testing on SMP can explore the bug. 2. Let umtx_wake returns number of threads have been woken.
2004-12-24 11:30:55 +00:00
if ((error = umtx_key_get(td, umtx, &key)) != 0)
return (error);
umtxq_lock(&key);
umtxq_busy(&key);
count = umtxq_count(&key);
umtxq_unlock(&key);
Move the decision on whether to unset the contested bit or not from lock to unlock time. Suggested by: jhb
2003-07-18 17:58:37 +00:00
/*
* When unlocking the umtx, it must be marked as unowned if
* there is zero or one thread only waiting for it.
* Otherwise, it must be marked as contested.
*/
1. Fix race condition between umtx lock and unlock, heavy testing on SMP can explore the bug. 2. Let umtx_wake returns number of threads have been woken.
2004-12-24 11:30:55 +00:00
old = casuptr((intptr_t *)&umtx->u_owner, owner,
count <= 1 ? UMTX_UNOWNED : UMTX_CONTESTED);
umtxq_lock(&key);
umtxq_signal(&key, 0);
umtxq_unbusy(&key);
umtxq_unlock(&key);
umtx_key_release(&key);
- Remove the blocked pointer from the umtx structure. - Use a hash of umtx queues to queue blocked threads. We hash on pid and the virtual address of the umtx structure. This eliminates cases where we previously held a lock across a casuptr call. Reviwed by: jhb (quickly)
2003-06-03 05:24:46 +00:00
if (old == -1)
return (EFAULT);
1. use per-chain mutex instead of global mutex to reduce lock collision. 2. Fix two race conditions. One is between _umtx_unlock and signal, also a thread was marked TDF_UMTXWAKEUP by _umtx_unlock, it is possible a signal delivered to the thread will cause msleep returns EINTR, and the thread breaks out of loop, this causes umtx ownership is not transfered to the thread. Another is in _umtx_unlock itself, when the function sets the umtx to UMTX_UNOWNED state, a new thread can come in and lock the umtx, also the function tries to set contested bit flag, but it will fail. Although the function will wake a blocked thread, if that thread breaks out of loop by signal, no contested bit will be set.
2004-11-30 12:02:53 +00:00
if (old != owner)
return (EINVAL);
- Remove the blocked pointer from the umtx structure. - Use a hash of umtx queues to queue blocked threads. We hash on pid and the virtual address of the umtx structure. This eliminates cases where we previously held a lock across a casuptr call. Reviwed by: jhb (quickly)
2003-06-03 05:24:46 +00:00
return (0);
- Add an api for doing smp safe locks in userland. - umtx_lock() is defined as an inline in umtx.h. It tries to do an uncontested acquire of a lock which falls back to the _umtx_lock() system-call if that fails. - umtx_unlock() is also an inline which falls back to _umtx_unlock() if the uncontested unlock fails. - Locks are keyed off of the thr_id_t of the currently running thread which is currently just the pointer to the 'struct thread' in kernel. - _umtx_lock() uses the proc pointer to synchronize access to blocked thread queues which are stored in the first blocked thread.
2003-04-01 01:10:42 +00:00
}
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
static int
Make umtx_wait and umtx_wake more like linux futex does, it is more general than previous. It also lets me implement cancelable point in thread library. Also in theory, umtx_lock and umtx_unlock can be implemented by using umtx_wait and umtx_wake, all atomic operations can be done in userland without kernel's casuptr() function.
2004-12-30 02:56:17 +00:00
do_wait(struct thread *td, struct umtx *umtx, long id, struct timespec *abstime)
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
{
struct umtx_q uq;
struct timespec ts1, ts2;
struct timeval tv;
Make umtx_wait and umtx_wake more like linux futex does, it is more general than previous. It also lets me implement cancelable point in thread library. Also in theory, umtx_lock and umtx_unlock can be implemented by using umtx_wait and umtx_wake, all atomic operations can be done in userland without kernel's casuptr() function.
2004-12-30 02:56:17 +00:00
long tmp;
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
int timo, error = 0;
Make umtx_wait and umtx_wake more like linux futex does, it is more general than previous. It also lets me implement cancelable point in thread library. Also in theory, umtx_lock and umtx_unlock can be implemented by using umtx_wait and umtx_wake, all atomic operations can be done in userland without kernel's casuptr() function.
2004-12-30 02:56:17 +00:00
if ((error = umtxq_queue_me(td, umtx, &uq)) != 0)
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
return (error);
Make umtx_wait and umtx_wake more like linux futex does, it is more general than previous. It also lets me implement cancelable point in thread library. Also in theory, umtx_lock and umtx_unlock can be implemented by using umtx_wait and umtx_wake, all atomic operations can be done in userland without kernel's casuptr() function.
2004-12-30 02:56:17 +00:00
tmp = fuword(&umtx->u_owner);
if (tmp != id) {
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
umtxq_lock(&uq.uq_key);
umtxq_remove(&uq);
umtxq_unlock(&uq.uq_key);
Make umtx_wait and umtx_wake more like linux futex does, it is more general than previous. It also lets me implement cancelable point in thread library. Also in theory, umtx_lock and umtx_unlock can be implemented by using umtx_wait and umtx_wake, all atomic operations can be done in userland without kernel's casuptr() function.
2004-12-30 02:56:17 +00:00
} else if (abstime == NULL) {
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
umtxq_lock(&uq.uq_key);
if (td->td_flags & TDF_UMTXQ)
error = umtxq_sleep(td, &uq.uq_key,
td->td_priority | PCATCH, "ucond", 0);
1. Fix race condition between umtx lock and unlock, heavy testing on SMP can explore the bug. 2. Let umtx_wake returns number of threads have been woken.
2004-12-24 11:30:55 +00:00
if (!(td->td_flags & TDF_UMTXQ))
error = 0;
else
umtxq_remove(&uq);
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
umtxq_unlock(&uq.uq_key);
} else {
for (;;) {
ts1 = *abstime;
getnanotime(&ts2);
timespecsub(&ts1, &ts2);
TIMESPEC_TO_TIMEVAL(&tv, &ts1);
1. Fix race condition between umtx lock and unlock, heavy testing on SMP can explore the bug. 2. Let umtx_wake returns number of threads have been woken.
2004-12-24 11:30:55 +00:00
umtxq_lock(&uq.uq_key);
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
if (tv.tv_sec < 0) {
Return ETIMEDOUT when thread is timeouted since POSIX thread APIs expect ETIMEDOUT not EAGAIN, this simplifies userland code a bit.
2005-01-06 02:08:34 +00:00
error = ETIMEDOUT;
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
break;
}
timo = tvtohz(&tv);
1. Fix race condition between umtx lock and unlock, heavy testing on SMP can explore the bug. 2. Let umtx_wake returns number of threads have been woken.
2004-12-24 11:30:55 +00:00
if (td->td_flags & TDF_UMTXQ)
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
error = umtxq_sleep(td, &uq.uq_key,
1. Fix race condition between umtx lock and unlock, heavy testing on SMP can explore the bug. 2. Let umtx_wake returns number of threads have been woken.
2004-12-24 11:30:55 +00:00
td->td_priority | PCATCH,
1. msleep returns EWOULDBLOCK not ETIMEDOUT, use EWOULDBLOCK instead. 2. Eliminate a possible lock leak in timed wait loop.
2004-12-18 13:43:16 +00:00
"ucond", timo);
1. introduce umtx_owner to get an owner of a umtx. 2. add const qualifier to umtx_timedlock and umtx_timedwait. 3. add missing blackets in umtx do_unlock_and_wait.
2004-12-25 12:49:35 +00:00
if (!(td->td_flags & TDF_UMTXQ))
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
break;
umtxq_unlock(&uq.uq_key);
}
1. Fix race condition between umtx lock and unlock, heavy testing on SMP can explore the bug. 2. Let umtx_wake returns number of threads have been woken.
2004-12-24 11:30:55 +00:00
if (!(td->td_flags & TDF_UMTXQ))
error = 0;
else
umtxq_remove(&uq);
umtxq_unlock(&uq.uq_key);
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
}
umtx_key_release(&uq.uq_key);
1. Fix race condition between umtx lock and unlock, heavy testing on SMP can explore the bug. 2. Let umtx_wake returns number of threads have been woken.
2004-12-24 11:30:55 +00:00
if (error == ERESTART)
error = EINTR;
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
return (error);
}
static int
1. Fix race condition between umtx lock and unlock, heavy testing on SMP can explore the bug. 2. Let umtx_wake returns number of threads have been woken.
2004-12-24 11:30:55 +00:00
do_wake(struct thread *td, void *uaddr, int n_wake)
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
{
struct umtx_key key;
1. Fix race condition between umtx lock and unlock, heavy testing on SMP can explore the bug. 2. Let umtx_wake returns number of threads have been woken.
2004-12-24 11:30:55 +00:00
int ret;
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
1. Fix race condition between umtx lock and unlock, heavy testing on SMP can explore the bug. 2. Let umtx_wake returns number of threads have been woken.
2004-12-24 11:30:55 +00:00
if ((ret = umtx_key_get(td, uaddr, &key)) != 0)
return (ret);
Add umtxq_lock/unlock around umtx_signal, fix debug kernel compiling, let umtx_lock returns EINTR when it returns ERESTART, this lets userland have chance to back off mtx lock code when needed.
2004-12-24 11:59:20 +00:00
umtxq_lock(&key);
1. Fix race condition between umtx lock and unlock, heavy testing on SMP can explore the bug. 2. Let umtx_wake returns number of threads have been woken.
2004-12-24 11:30:55 +00:00
ret = umtxq_signal(&key, n_wake);
Add umtxq_lock/unlock around umtx_signal, fix debug kernel compiling, let umtx_lock returns EINTR when it returns ERESTART, this lets userland have chance to back off mtx lock code when needed.
2004-12-24 11:59:20 +00:00
umtxq_unlock(&key);
1. Fix race condition between umtx lock and unlock, heavy testing on SMP can explore the bug. 2. Let umtx_wake returns number of threads have been woken.
2004-12-24 11:30:55 +00:00
umtx_key_release(&key);
td->td_retval[0] = ret;
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
return (0);
}
int
_umtx_lock(struct thread *td, struct _umtx_lock_args *uap)
/* struct umtx *umtx */
{
return _do_lock(td, uap->umtx, td->td_tid, 0);
}
int
_umtx_unlock(struct thread *td, struct _umtx_unlock_args *uap)
/* struct umtx *umtx */
{
return do_unlock(td, uap->umtx, td->td_tid);
}
int
_umtx_op(struct thread *td, struct _umtx_op_args *uap)
{
struct timespec abstime;
struct timespec *ts;
int error;
switch(uap->op) {
case UMTX_OP_LOCK:
/* Allow a null timespec (wait forever). */
Make _umtx_op() as more general interface, the final parameter needn't be timespec pointer, every parameter will be interpreted by its opcode.
2004-12-25 13:02:50 +00:00
if (uap->uaddr2 == NULL)
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
ts = NULL;
else {
Make _umtx_op() as more general interface, the final parameter needn't be timespec pointer, every parameter will be interpreted by its opcode.
2004-12-25 13:02:50 +00:00
error = copyin(uap->uaddr2, &abstime, sizeof(abstime));
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
if (error != 0)
return (error);
if (abstime.tv_nsec >= 1000000000 ||
abstime.tv_nsec < 0)
return (EINVAL);
ts = &abstime;
}
return do_lock(td, uap->umtx, uap->id, ts);
case UMTX_OP_UNLOCK:
return do_unlock(td, uap->umtx, uap->id);
Make umtx_wait and umtx_wake more like linux futex does, it is more general than previous. It also lets me implement cancelable point in thread library. Also in theory, umtx_lock and umtx_unlock can be implemented by using umtx_wait and umtx_wake, all atomic operations can be done in userland without kernel's casuptr() function.
2004-12-30 02:56:17 +00:00
case UMTX_OP_WAIT:
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
/* Allow a null timespec (wait forever). */
Make _umtx_op() as more general interface, the final parameter needn't be timespec pointer, every parameter will be interpreted by its opcode.
2004-12-25 13:02:50 +00:00
if (uap->uaddr2 == NULL)
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
ts = NULL;
else {
Make _umtx_op() as more general interface, the final parameter needn't be timespec pointer, every parameter will be interpreted by its opcode.
2004-12-25 13:02:50 +00:00
error = copyin(uap->uaddr2, &abstime, sizeof(abstime));
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
if (error != 0)
return (error);
if (abstime.tv_nsec >= 1000000000 ||
abstime.tv_nsec < 0)
return (EINVAL);
ts = &abstime;
}
Make umtx_wait and umtx_wake more like linux futex does, it is more general than previous. It also lets me implement cancelable point in thread library. Also in theory, umtx_lock and umtx_unlock can be implemented by using umtx_wait and umtx_wake, all atomic operations can be done in userland without kernel's casuptr() function.
2004-12-30 02:56:17 +00:00
return do_wait(td, uap->umtx, uap->id, ts);
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
case UMTX_OP_WAKE:
Make umtx_wait and umtx_wake more like linux futex does, it is more general than previous. It also lets me implement cancelable point in thread library. Also in theory, umtx_lock and umtx_unlock can be implemented by using umtx_wait and umtx_wake, all atomic operations can be done in userland without kernel's casuptr() function.
2004-12-30 02:56:17 +00:00
return do_wake(td, uap->umtx, uap->id);
1. make umtx sharable between processes, the way is two or more processes call mmap() to create a shared space, and then initialize umtx on it, after that, each thread in different processes can use the umtx same as threads in same process. 2. introduce a new syscall _umtx_op to support timed lock and condition variable semantics. also, orignal umtx_lock and umtx_unlock inline functions now are reimplemented by using _umtx_op, the _umtx_op can use arbitrary id not just a thread id.
2004-12-18 12:52:44 +00:00
default:
return (EINVAL);
}
}
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