freebsd-dev/sys/kern/kern_umtx.c
David Xu a2cc61fa6e Revert my previous errno hack, that is certainly an issue,
and always has been, but the system call itself returns
errno in a register so the problem is really a function of
libc, not the system call.

Discussed with : Matthew Dillion <dillon@apollo.backplane.com>
2005-01-18 13:53:10 +00:00

761 lines
18 KiB
C

/*-
* Copyright (c) 2004, David Xu <davidxu@freebsd.org>
* 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.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/limits.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/sysent.h>
#include <sys/systm.h>
#include <sys/sysproto.h>
#include <sys/eventhandler.h>
#include <sys/thr.h>
#include <sys/umtx.h>
#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;
};
struct umtx_q {
LIST_ENTRY(umtx_q) uq_next; /* Linked list for the hash. */
struct umtx_key uq_key; /* Umtx key. */
struct thread *uq_thread; /* The thread waits on. */
LIST_ENTRY(umtx_q) uq_rqnext; /* Linked list for requeuing. */
vm_offset_t uq_addr; /* Umtx's virtual address. */
};
LIST_HEAD(umtx_head, umtx_q);
struct umtxq_chain {
struct mtx uc_lock; /* Lock for this chain. */
struct umtx_head uc_queue; /* List of sleep queues. */
#define UCF_BUSY 0x01
#define UCF_WANT 0x02
int uc_flags;
};
#define GOLDEN_RATIO_PRIME 2654404609U
#define UMTX_CHAINS 128
#define UMTX_SHIFTS (__WORD_BIT - 7)
static struct umtxq_chain umtxq_chains[UMTX_CHAINS];
static MALLOC_DEFINE(M_UMTX, "umtx", "UMTX queue memory");
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);
static void umtxq_busy(struct umtx_key *key);
static void umtxq_unbusy(struct umtx_key *key);
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);
static int umtxq_count(struct umtx_key *key);
static int umtxq_signal(struct umtx_key *key, int nr_wakeup);
#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);
static void
umtxq_init_chains(void *arg __unused)
{
int i;
for (i = 0; i < UMTX_CHAINS; ++i) {
mtx_init(&umtxq_chains[i].uc_lock, "umtxq_lock", NULL,
MTX_DEF | MTX_DUPOK);
LIST_INIT(&umtxq_chains[i].uc_queue);
umtxq_chains[i].uc_flags = 0;
}
#ifdef UMTX_DYNAMIC_SHARED
EVENTHANDLER_REGISTER(process_fork, fork_handler, 0, 10000);
#endif
}
static inline int
umtxq_hash(struct umtx_key *key)
{
unsigned n = (uintptr_t)key->info.both.ptr + key->info.both.word;
return (((n * GOLDEN_RATIO_PRIME) >> UMTX_SHIFTS) % UMTX_CHAINS);
}
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);
}
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);
KASSERT(umtxq_chains[chain].uc_flags & UCF_BUSY, ("not busy"));
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]);
}
}
static inline void
umtxq_lock(struct umtx_key *key)
{
int chain = umtxq_hash(key);
mtx_lock(umtxq_mtx(chain));
}
static inline void
umtxq_unlock(struct umtx_key *key)
{
int chain = umtxq_hash(key);
mtx_unlock(umtxq_mtx(chain));
}
/*
* Insert a thread onto the umtx queue.
*/
static inline void
umtxq_insert(struct umtx_q *uq)
{
struct umtx_head *head;
int chain = umtxq_hash(&uq->uq_key);
mtx_assert(umtxq_mtx(chain), MA_OWNED);
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)
{
mtx_assert(umtxq_mtx(umtxq_hash(&uq->uq_key)), MA_OWNED);
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)
{
struct umtx_q *uq;
struct umtx_head *head;
int chain, count = 0;
chain = umtxq_hash(key);
mtx_assert(umtxq_mtx(chain), MA_OWNED);
head = &umtxq_chains[chain].uc_queue;
LIST_FOREACH(uq, head, uq_next) {
if (umtx_key_match(&uq->uq_key, key)) {
if (++count > 1)
break;
}
}
return (count);
}
static int
umtxq_signal(struct umtx_key *key, int n_wake)
{
struct umtx_q *uq, *next;
struct umtx_head *head;
struct thread *blocked = NULL;
int chain, ret;
ret = 0;
chain = umtxq_hash(key);
mtx_assert(umtxq_mtx(chain), MA_OWNED);
head = &umtxq_chains[chain].uc_queue;
for (uq = LIST_FIRST(head); uq; uq = next) {
next = LIST_NEXT(uq, uq_next);
if (umtx_key_match(&uq->uq_key, key)) {
blocked = uq->uq_thread;
umtxq_remove(uq);
wakeup(blocked);
if (++ret >= n_wake)
break;
}
}
return (ret);
}
static inline int
umtxq_sleep(struct thread *td, struct umtx_key *key, int priority,
const char *wmesg, int timo)
{
int chain = umtxq_hash(key);
int error = msleep(td, umtxq_mtx(chain), priority, wmesg, timo);
if (error == EWOULDBLOCK)
error = ETIMEDOUT;
return (error);
}
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);
}
static inline int
umtxq_queue_me(struct thread *td, struct umtx *umtx, struct umtx_q *uq)
{
int error;
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);
/* hmm, for condition variable, we don't need busy flag. */
umtxq_busy(&uq->uq_key);
umtxq_insert(uq);
umtxq_unbusy(&uq->uq_key);
umtxq_unlock(&uq->uq_key);
return (0);
}
#if defined(UMTX_DYNAMIC_SHARED)
static void
fork_handler(void *arg, struct proc *p1, struct proc *p2, int flags)
{
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;
struct umtx_q *uq;
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);
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;
}
umtxq_lock(&uq->uq_key);
umtxq_busy(&uq->uq_key);
if (uq->uq_thread->td_flags & TDF_UMTXQ) {
umtxq_remove(uq);
onq = 1;
} else
onq = 0;
umtxq_unbusy(&uq->uq_key);
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);
umtxq_busy(&uq->uq_key);
umtxq_insert(uq);
umtxq_unbusy(&uq->uq_key);
umtxq_unlock(&uq->uq_key);
vm_object_reference(uq->uq_key.info.shared.object);
}
vm_map_lookup_done(map, entry);
}
}
#endif
static int
_do_lock(struct thread *td, struct umtx *umtx, long id, int timo)
{
struct umtx_q uq;
intptr_t owner;
intptr_t old;
int error = 0;
/*
* Care must be exercised when dealing with umtx structure. It
* can fault on any access.
*/
for (;;) {
/*
* Try the uncontested case. This should be done in userland.
*/
owner = casuptr((intptr_t *)&umtx->u_owner,
UMTX_UNOWNED, id);
/* The acquire succeeded. */
if (owner == UMTX_UNOWNED)
return (0);
/* The address was invalid. */
if (owner == -1)
return (EFAULT);
/* If no one owns it but it is contested try to acquire it. */
if (owner == UMTX_CONTESTED) {
owner = casuptr((intptr_t *)&umtx->u_owner,
UMTX_CONTESTED, id | UMTX_CONTESTED);
if (owner == UMTX_CONTESTED)
return (0);
/* The address was invalid. */
if (owner == -1)
return (EFAULT);
/* If this failed the lock has changed, restart. */
continue;
}
/*
* If we caught a signal, we have retried and now
* exit immediately.
*/
if (error || (error = umtxq_queue_me(td, umtx, &uq)) != 0)
return (error);
/*
* 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.
*/
old = casuptr((intptr_t *)&umtx->u_owner, owner,
owner | UMTX_CONTESTED);
/* The address was invalid. */
if (old == -1) {
umtxq_lock(&uq.uq_key);
umtxq_busy(&uq.uq_key);
umtxq_remove(&uq);
umtxq_unbusy(&uq.uq_key);
umtxq_unlock(&uq.uq_key);
umtx_key_release(&uq.uq_key);
return (EFAULT);
}
/*
* We set the contested bit, sleep. Otherwise the lock changed
* and we need to retry or we lost a race to the thread
* unlocking the umtx.
*/
umtxq_lock(&uq.uq_key);
if (old == owner && (td->td_flags & TDF_UMTXQ)) {
error = umtxq_sleep(td, &uq.uq_key,
td->td_priority | PCATCH,
"umtx", timo);
}
umtxq_busy(&uq.uq_key);
umtxq_remove(&uq);
umtxq_unbusy(&uq.uq_key);
umtxq_unlock(&uq.uq_key);
umtx_key_release(&uq.uq_key);
}
return (0);
}
static int
do_lock(struct thread *td, struct umtx *umtx, long id,
struct timespec *timeout)
{
struct timespec ts, ts2, ts3;
struct timeval tv;
int error;
if (timeout == NULL) {
error = _do_lock(td, umtx, id, 0);
} else {
getnanouptime(&ts);
timespecadd(&ts, timeout);
TIMESPEC_TO_TIMEVAL(&tv, timeout);
for (;;) {
error = _do_lock(td, umtx, id, tvtohz(&tv));
if (error != ETIMEDOUT)
break;
getnanouptime(&ts2);
if (timespeccmp(&ts2, &ts, >=)) {
error = ETIMEDOUT;
break;
}
ts3 = ts;
timespecsub(&ts3, &ts2);
TIMESPEC_TO_TIMEVAL(&tv, &ts3);
}
}
/*
* This lets userland back off critical region if needed.
*/
if (error == ERESTART)
error = EINTR;
return (error);
}
static int
do_unlock(struct thread *td, struct umtx *umtx, long id)
{
struct umtx_key key;
intptr_t owner;
intptr_t old;
int error;
int count;
/*
* Make sure we own this mtx.
*
* XXX Need a {fu,su}ptr this is not correct on arch where
* sizeof(intptr_t) != sizeof(long).
*/
if ((owner = fuword(&umtx->u_owner)) == -1)
return (EFAULT);
if ((owner & ~UMTX_CONTESTED) != id)
return (EPERM);
/* We should only ever be in here for contested locks */
if ((owner & UMTX_CONTESTED) == 0)
return (EINVAL);
if ((error = umtx_key_get(td, umtx, &key)) != 0)
return (error);
umtxq_lock(&key);
umtxq_busy(&key);
count = umtxq_count(&key);
umtxq_unlock(&key);
/*
* 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.
*/
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);
if (old == -1)
return (EFAULT);
if (old != owner)
return (EINVAL);
return (0);
}
static int
do_wait(struct thread *td, struct umtx *umtx, long id, struct timespec *timeout)
{
struct umtx_q uq;
struct timespec ts, ts2, ts3;
struct timeval tv;
long tmp;
int error = 0;
if ((error = umtxq_queue_me(td, umtx, &uq)) != 0)
return (error);
tmp = fuword(&umtx->u_owner);
if (tmp != id) {
umtxq_lock(&uq.uq_key);
umtxq_remove(&uq);
umtxq_unlock(&uq.uq_key);
} else if (timeout == NULL) {
umtxq_lock(&uq.uq_key);
if (td->td_flags & TDF_UMTXQ)
error = umtxq_sleep(td, &uq.uq_key,
td->td_priority | PCATCH, "ucond", 0);
if (!(td->td_flags & TDF_UMTXQ))
error = 0;
else
umtxq_remove(&uq);
umtxq_unlock(&uq.uq_key);
} else {
getnanouptime(&ts);
timespecadd(&ts, timeout);
TIMESPEC_TO_TIMEVAL(&tv, timeout);
for (;;) {
umtxq_lock(&uq.uq_key);
if (td->td_flags & TDF_UMTXQ) {
error = umtxq_sleep(td, &uq.uq_key,
td->td_priority | PCATCH,
"ucond", tvtohz(&tv));
}
if (!(td->td_flags & TDF_UMTXQ)) {
umtxq_unlock(&uq.uq_key);
goto out;
}
umtxq_unlock(&uq.uq_key);
if (error != ETIMEDOUT)
break;
getnanouptime(&ts2);
if (timespeccmp(&ts2, &ts, >=)) {
error = ETIMEDOUT;
break;
}
ts3 = ts;
timespecsub(&ts3, &ts2);
TIMESPEC_TO_TIMEVAL(&tv, &ts3);
}
umtxq_lock(&uq.uq_key);
umtxq_remove(&uq);
umtxq_unlock(&uq.uq_key);
}
out:
umtx_key_release(&uq.uq_key);
if (error == ERESTART)
error = EINTR;
return (error);
}
static int
do_wake(struct thread *td, void *uaddr, int n_wake)
{
struct umtx_key key;
int ret;
if ((ret = umtx_key_get(td, uaddr, &key)) != 0)
return (ret);
umtxq_lock(&key);
ret = umtxq_signal(&key, n_wake);
umtxq_unlock(&key);
umtx_key_release(&key);
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 timeout;
struct timespec *ts;
int error;
switch(uap->op) {
case UMTX_OP_LOCK:
/* Allow a null timespec (wait forever). */
if (uap->uaddr2 == NULL)
ts = NULL;
else {
error = copyin(uap->uaddr2, &timeout, sizeof(timeout));
if (error != 0)
break;
if (timeout.tv_nsec >= 1000000000 ||
timeout.tv_nsec < 0) {
error = EINVAL;
break;
}
ts = &timeout;
}
error = do_lock(td, uap->umtx, uap->id, ts);
break;
case UMTX_OP_UNLOCK:
error = do_unlock(td, uap->umtx, uap->id);
break;
case UMTX_OP_WAIT:
/* Allow a null timespec (wait forever). */
if (uap->uaddr2 == NULL)
ts = NULL;
else {
error = copyin(uap->uaddr2, &timeout, sizeof(timeout));
if (error != 0)
break;
if (timeout.tv_nsec >= 1000000000 ||
timeout.tv_nsec < 0) {
error = EINVAL;
break;
}
ts = &timeout;
}
error = do_wait(td, uap->umtx, uap->id, ts);
break;
case UMTX_OP_WAKE:
error = do_wake(td, uap->umtx, uap->id);
break;
default:
error = EINVAL;
break;
}
return (error);
}