freebsd-dev/sys/kern/kern_thread.c

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/*
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* Copyright (C) 2001 Julian Elischer <julian@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(s), this list of conditions and the following disclaimer as
* the first lines of this file unmodified other than the possible
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* addition of one or more copyright notices.
* 2. Redistributions in binary form must reproduce the above copyright
* notice(s), 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 COPYRIGHT HOLDER(S) ``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 COPYRIGHT HOLDER(S) 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.
*/
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#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
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#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/proc.h>
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#include <sys/smp.h>
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#include <sys/sysctl.h>
#include <sys/sched.h>
Switch the sleep/wakeup and condition variable implementations to use the sleep queue interface: - Sleep queues attempt to merge some of the benefits of both sleep queues and condition variables. Having sleep qeueus in a hash table avoids having to allocate a queue head for each wait channel. Thus, struct cv has shrunk down to just a single char * pointer now. However, the hash table does not hold threads directly, but queue heads. This means that once you have located a queue in the hash bucket, you no longer have to walk the rest of the hash chain looking for threads. Instead, you have a list of all the threads sleeping on that wait channel. - Outside of the sleepq code and the sleep/cv code the kernel no longer differentiates between cv's and sleep/wakeup. For example, calls to abortsleep() and cv_abort() are replaced with a call to sleepq_abort(). Thus, the TDF_CVWAITQ flag is removed. Also, calls to unsleep() and cv_waitq_remove() have been replaced with calls to sleepq_remove(). - The sched_sleep() function no longer accepts a priority argument as sleep's no longer inherently bump the priority. Instead, this is soley a propery of msleep() which explicitly calls sched_prio() before blocking. - The TDF_ONSLEEPQ flag has been dropped as it was never used. The associated TDF_SET_ONSLEEPQ and TDF_CLR_ON_SLEEPQ macros have also been dropped and replaced with a single explicit clearing of td_wchan. TD_SET_ONSLEEPQ() would really have only made sense if it had taken the wait channel and message as arguments anyway. Now that that only happens in one place, a macro would be overkill.
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#include <sys/sleepqueue.h>
Add an implementation of turnstiles and change the sleep mutex code to use turnstiles to implement blocking isntead of implementing a thread queue directly. These turnstiles are somewhat similar to those used in Solaris 7 as described in Solaris Internals but are also different. Turnstiles do not come out of a fixed-sized pool. Rather, each thread is assigned a turnstile when it is created that it frees when it is destroyed. When a thread blocks on a lock, it donates its turnstile to that lock to serve as queue of blocked threads. The queue associated with a given lock is found by a lookup in a simple hash table. The turnstile itself is protected by a lock associated with its entry in the hash table. This means that sched_lock is no longer needed to contest on a mutex. Instead, sched_lock is only used when manipulating run queues or thread priorities. Turnstiles also implement priority propagation inherently. Currently turnstiles only support mutexes. Eventually, however, turnstiles may grow two queue's to support a non-sleepable reader/writer lock implementation. For more details, see the comments in sys/turnstile.h and kern/subr_turnstile.c. The two primary advantages from the turnstile code include: 1) the size of struct mutex shrinks by four pointers as it no longer stores the thread queue linkages directly, and 2) less contention on sched_lock in SMP systems including the ability for multiple CPUs to contend on different locks simultaneously (not that this last detail is necessarily that much of a big win). Note that 1) means that this commit is a kernel ABI breaker, so don't mix old modules with a new kernel and vice versa. Tested on: i386 SMP, sparc64 SMP, alpha SMP
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#include <sys/turnstile.h>
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#include <sys/ktr.h>
#include <vm/vm.h>
#include <vm/vm_extern.h>
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#include <vm/uma.h>
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/*
* KSEGRP related storage.
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*/
static uma_zone_t ksegrp_zone;
static uma_zone_t kse_zone;
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static uma_zone_t thread_zone;
/* DEBUG ONLY */
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SYSCTL_NODE(_kern, OID_AUTO, threads, CTLFLAG_RW, 0, "thread allocation");
static int thread_debug = 0;
SYSCTL_INT(_kern_threads, OID_AUTO, debug, CTLFLAG_RW,
&thread_debug, 0, "thread debug");
int max_threads_per_proc = 1500;
SYSCTL_INT(_kern_threads, OID_AUTO, max_threads_per_proc, CTLFLAG_RW,
&max_threads_per_proc, 0, "Limit on threads per proc");
int max_groups_per_proc = 500;
SYSCTL_INT(_kern_threads, OID_AUTO, max_groups_per_proc, CTLFLAG_RW,
&max_groups_per_proc, 0, "Limit on thread groups per proc");
int max_threads_hits;
SYSCTL_INT(_kern_threads, OID_AUTO, max_threads_hits, CTLFLAG_RD,
&max_threads_hits, 0, "");
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int virtual_cpu;
#define RANGEOF(type, start, end) (offsetof(type, end) - offsetof(type, start))
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TAILQ_HEAD(, thread) zombie_threads = TAILQ_HEAD_INITIALIZER(zombie_threads);
TAILQ_HEAD(, kse) zombie_kses = TAILQ_HEAD_INITIALIZER(zombie_kses);
TAILQ_HEAD(, ksegrp) zombie_ksegrps = TAILQ_HEAD_INITIALIZER(zombie_ksegrps);
struct mtx kse_zombie_lock;
MTX_SYSINIT(kse_zombie_lock, &kse_zombie_lock, "kse zombie lock", MTX_SPIN);
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void kse_purge(struct proc *p, struct thread *td);
void kse_purge_group(struct thread *td);
/* move to proc.h */
extern void kseinit(void);
extern void kse_GC(void);
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static int
sysctl_kse_virtual_cpu(SYSCTL_HANDLER_ARGS)
{
int error, new_val;
int def_val;
def_val = mp_ncpus;
if (virtual_cpu == 0)
new_val = def_val;
else
new_val = virtual_cpu;
error = sysctl_handle_int(oidp, &new_val, 0, req);
if (error != 0 || req->newptr == NULL)
return (error);
if (new_val < 0)
return (EINVAL);
virtual_cpu = new_val;
return (0);
}
/* DEBUG ONLY */
SYSCTL_PROC(_kern_threads, OID_AUTO, virtual_cpu, CTLTYPE_INT|CTLFLAG_RW,
0, sizeof(virtual_cpu), sysctl_kse_virtual_cpu, "I",
"debug virtual cpus");
/*
* Thread ID allocator. The allocator keeps track of assigned IDs by
* using a bitmap. The bitmap is created in parts. The parts are linked
* together.
*/
typedef u_long tid_bitmap_word;
#define TID_IDS_PER_PART 1024
#define TID_IDS_PER_IDX (sizeof(tid_bitmap_word) << 3)
#define TID_BITMAP_SIZE (TID_IDS_PER_PART / TID_IDS_PER_IDX)
#define TID_MIN (PID_MAX + 1)
struct tid_bitmap_part {
STAILQ_ENTRY(tid_bitmap_part) bmp_next;
tid_bitmap_word bmp_bitmap[TID_BITMAP_SIZE];
lwpid_t bmp_base;
int bmp_free;
};
static STAILQ_HEAD(, tid_bitmap_part) tid_bitmap =
STAILQ_HEAD_INITIALIZER(tid_bitmap);
static uma_zone_t tid_zone;
struct mtx tid_lock;
MTX_SYSINIT(tid_lock, &tid_lock, "TID lock", MTX_DEF);
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/*
* Prepare a thread for use.
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*/
static void
thread_ctor(void *mem, int size, void *arg)
{
struct thread *td;
td = (struct thread *)mem;
td->td_tid = 0;
td->td_state = TDS_INACTIVE;
td->td_oncpu = NOCPU;
/*
* Note that td_critnest begins life as 1 because the thread is not
* running and is thereby implicitly waiting to be on the receiving
* end of a context switch. A context switch must occur inside a
* critical section, and in fact, includes hand-off of the sched_lock.
* After a context switch to a newly created thread, it will release
* sched_lock for the first time, and its td_critnest will hit 0 for
* the first time. This happens on the far end of a context switch,
* and when it context switches away from itself, it will in fact go
* back into a critical section, and hand off the sched lock to the
* next thread.
*/
td->td_critnest = 1;
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}
/*
* Reclaim a thread after use.
*/
static void
thread_dtor(void *mem, int size, void *arg)
{
struct thread *td;
struct tid_bitmap_part *bmp;
lwpid_t tid;
int bit, idx;
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td = (struct thread *)mem;
if (td->td_tid > PID_MAX) {
STAILQ_FOREACH(bmp, &tid_bitmap, bmp_next) {
if (td->td_tid >= bmp->bmp_base &&
td->td_tid < bmp->bmp_base + TID_IDS_PER_PART)
break;
}
KASSERT(bmp != NULL, ("No TID bitmap?"));
mtx_lock(&tid_lock);
tid = td->td_tid - bmp->bmp_base;
idx = tid / TID_IDS_PER_IDX;
bit = 1UL << (tid % TID_IDS_PER_IDX);
bmp->bmp_bitmap[idx] |= bit;
bmp->bmp_free++;
mtx_unlock(&tid_lock);
}
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#ifdef INVARIANTS
/* Verify that this thread is in a safe state to free. */
switch (td->td_state) {
case TDS_INHIBITED:
case TDS_RUNNING:
case TDS_CAN_RUN:
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case TDS_RUNQ:
/*
* We must never unlink a thread that is in one of
* these states, because it is currently active.
*/
panic("bad state for thread unlinking");
/* NOTREACHED */
case TDS_INACTIVE:
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break;
default:
panic("bad thread state");
/* NOTREACHED */
}
#endif
}
/*
* Initialize type-stable parts of a thread (when newly created).
*/
static void
thread_init(void *mem, int size)
{
struct thread *td;
td = (struct thread *)mem;
vm_thread_new(td, 0);
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cpu_thread_setup(td);
Switch the sleep/wakeup and condition variable implementations to use the sleep queue interface: - Sleep queues attempt to merge some of the benefits of both sleep queues and condition variables. Having sleep qeueus in a hash table avoids having to allocate a queue head for each wait channel. Thus, struct cv has shrunk down to just a single char * pointer now. However, the hash table does not hold threads directly, but queue heads. This means that once you have located a queue in the hash bucket, you no longer have to walk the rest of the hash chain looking for threads. Instead, you have a list of all the threads sleeping on that wait channel. - Outside of the sleepq code and the sleep/cv code the kernel no longer differentiates between cv's and sleep/wakeup. For example, calls to abortsleep() and cv_abort() are replaced with a call to sleepq_abort(). Thus, the TDF_CVWAITQ flag is removed. Also, calls to unsleep() and cv_waitq_remove() have been replaced with calls to sleepq_remove(). - The sched_sleep() function no longer accepts a priority argument as sleep's no longer inherently bump the priority. Instead, this is soley a propery of msleep() which explicitly calls sched_prio() before blocking. - The TDF_ONSLEEPQ flag has been dropped as it was never used. The associated TDF_SET_ONSLEEPQ and TDF_CLR_ON_SLEEPQ macros have also been dropped and replaced with a single explicit clearing of td_wchan. TD_SET_ONSLEEPQ() would really have only made sense if it had taken the wait channel and message as arguments anyway. Now that that only happens in one place, a macro would be overkill.
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td->td_sleepqueue = sleepq_alloc();
Add an implementation of turnstiles and change the sleep mutex code to use turnstiles to implement blocking isntead of implementing a thread queue directly. These turnstiles are somewhat similar to those used in Solaris 7 as described in Solaris Internals but are also different. Turnstiles do not come out of a fixed-sized pool. Rather, each thread is assigned a turnstile when it is created that it frees when it is destroyed. When a thread blocks on a lock, it donates its turnstile to that lock to serve as queue of blocked threads. The queue associated with a given lock is found by a lookup in a simple hash table. The turnstile itself is protected by a lock associated with its entry in the hash table. This means that sched_lock is no longer needed to contest on a mutex. Instead, sched_lock is only used when manipulating run queues or thread priorities. Turnstiles also implement priority propagation inherently. Currently turnstiles only support mutexes. Eventually, however, turnstiles may grow two queue's to support a non-sleepable reader/writer lock implementation. For more details, see the comments in sys/turnstile.h and kern/subr_turnstile.c. The two primary advantages from the turnstile code include: 1) the size of struct mutex shrinks by four pointers as it no longer stores the thread queue linkages directly, and 2) less contention on sched_lock in SMP systems including the ability for multiple CPUs to contend on different locks simultaneously (not that this last detail is necessarily that much of a big win). Note that 1) means that this commit is a kernel ABI breaker, so don't mix old modules with a new kernel and vice versa. Tested on: i386 SMP, sparc64 SMP, alpha SMP
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td->td_turnstile = turnstile_alloc();
td->td_sched = (struct td_sched *)&td[1];
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}
/*
* Tear down type-stable parts of a thread (just before being discarded).
*/
static void
thread_fini(void *mem, int size)
{
struct thread *td;
td = (struct thread *)mem;
Add an implementation of turnstiles and change the sleep mutex code to use turnstiles to implement blocking isntead of implementing a thread queue directly. These turnstiles are somewhat similar to those used in Solaris 7 as described in Solaris Internals but are also different. Turnstiles do not come out of a fixed-sized pool. Rather, each thread is assigned a turnstile when it is created that it frees when it is destroyed. When a thread blocks on a lock, it donates its turnstile to that lock to serve as queue of blocked threads. The queue associated with a given lock is found by a lookup in a simple hash table. The turnstile itself is protected by a lock associated with its entry in the hash table. This means that sched_lock is no longer needed to contest on a mutex. Instead, sched_lock is only used when manipulating run queues or thread priorities. Turnstiles also implement priority propagation inherently. Currently turnstiles only support mutexes. Eventually, however, turnstiles may grow two queue's to support a non-sleepable reader/writer lock implementation. For more details, see the comments in sys/turnstile.h and kern/subr_turnstile.c. The two primary advantages from the turnstile code include: 1) the size of struct mutex shrinks by four pointers as it no longer stores the thread queue linkages directly, and 2) less contention on sched_lock in SMP systems including the ability for multiple CPUs to contend on different locks simultaneously (not that this last detail is necessarily that much of a big win). Note that 1) means that this commit is a kernel ABI breaker, so don't mix old modules with a new kernel and vice versa. Tested on: i386 SMP, sparc64 SMP, alpha SMP
2003-11-11 22:07:29 +00:00
turnstile_free(td->td_turnstile);
Switch the sleep/wakeup and condition variable implementations to use the sleep queue interface: - Sleep queues attempt to merge some of the benefits of both sleep queues and condition variables. Having sleep qeueus in a hash table avoids having to allocate a queue head for each wait channel. Thus, struct cv has shrunk down to just a single char * pointer now. However, the hash table does not hold threads directly, but queue heads. This means that once you have located a queue in the hash bucket, you no longer have to walk the rest of the hash chain looking for threads. Instead, you have a list of all the threads sleeping on that wait channel. - Outside of the sleepq code and the sleep/cv code the kernel no longer differentiates between cv's and sleep/wakeup. For example, calls to abortsleep() and cv_abort() are replaced with a call to sleepq_abort(). Thus, the TDF_CVWAITQ flag is removed. Also, calls to unsleep() and cv_waitq_remove() have been replaced with calls to sleepq_remove(). - The sched_sleep() function no longer accepts a priority argument as sleep's no longer inherently bump the priority. Instead, this is soley a propery of msleep() which explicitly calls sched_prio() before blocking. - The TDF_ONSLEEPQ flag has been dropped as it was never used. The associated TDF_SET_ONSLEEPQ and TDF_CLR_ON_SLEEPQ macros have also been dropped and replaced with a single explicit clearing of td_wchan. TD_SET_ONSLEEPQ() would really have only made sense if it had taken the wait channel and message as arguments anyway. Now that that only happens in one place, a macro would be overkill.
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sleepq_free(td->td_sleepqueue);
vm_thread_dispose(td);
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}
/*
* Initialize type-stable parts of a kse (when newly created).
*/
static void
kse_init(void *mem, int size)
{
struct kse *ke;
ke = (struct kse *)mem;
ke->ke_sched = (struct ke_sched *)&ke[1];
}
/*
* Initialize type-stable parts of a ksegrp (when newly created).
*/
static void
ksegrp_init(void *mem, int size)
{
struct ksegrp *kg;
kg = (struct ksegrp *)mem;
kg->kg_sched = (struct kg_sched *)&kg[1];
}
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/*
* KSE is linked into kse group.
*/
void
kse_link(struct kse *ke, struct ksegrp *kg)
{
struct proc *p = kg->kg_proc;
TAILQ_INSERT_HEAD(&kg->kg_kseq, ke, ke_kglist);
kg->kg_kses++;
ke->ke_state = KES_UNQUEUED;
ke->ke_proc = p;
ke->ke_ksegrp = kg;
ke->ke_thread = NULL;
ke->ke_oncpu = NOCPU;
ke->ke_flags = 0;
}
void
kse_unlink(struct kse *ke)
{
struct ksegrp *kg;
mtx_assert(&sched_lock, MA_OWNED);
kg = ke->ke_ksegrp;
TAILQ_REMOVE(&kg->kg_kseq, ke, ke_kglist);
if (ke->ke_state == KES_IDLE) {
TAILQ_REMOVE(&kg->kg_iq, ke, ke_kgrlist);
kg->kg_idle_kses--;
}
--kg->kg_kses;
/*
* Aggregate stats from the KSE
*/
kse_stash(ke);
}
void
ksegrp_link(struct ksegrp *kg, struct proc *p)
{
TAILQ_INIT(&kg->kg_threads);
TAILQ_INIT(&kg->kg_runq); /* links with td_runq */
TAILQ_INIT(&kg->kg_slpq); /* links with td_runq */
TAILQ_INIT(&kg->kg_kseq); /* all kses in ksegrp */
TAILQ_INIT(&kg->kg_iq); /* all idle kses in ksegrp */
TAILQ_INIT(&kg->kg_upcalls); /* all upcall structure in ksegrp */
kg->kg_proc = p;
/*
* the following counters are in the -zero- section
* and may not need clearing
*/
kg->kg_numthreads = 0;
kg->kg_runnable = 0;
kg->kg_kses = 0;
kg->kg_runq_kses = 0; /* XXXKSE change name */
kg->kg_idle_kses = 0;
kg->kg_numupcalls = 0;
/* link it in now that it's consistent */
p->p_numksegrps++;
TAILQ_INSERT_HEAD(&p->p_ksegrps, kg, kg_ksegrp);
}
void
ksegrp_unlink(struct ksegrp *kg)
{
struct proc *p;
mtx_assert(&sched_lock, MA_OWNED);
KASSERT((kg->kg_numthreads == 0), ("ksegrp_unlink: residual threads"));
KASSERT((kg->kg_kses == 0), ("ksegrp_unlink: residual kses"));
KASSERT((kg->kg_numupcalls == 0), ("ksegrp_unlink: residual upcalls"));
p = kg->kg_proc;
TAILQ_REMOVE(&p->p_ksegrps, kg, kg_ksegrp);
p->p_numksegrps--;
/*
* Aggregate stats from the KSE
*/
ksegrp_stash(kg);
}
/*
* For a newly created process,
* link up all the structures and its initial threads etc.
*/
void
proc_linkup(struct proc *p, struct ksegrp *kg,
struct kse *ke, struct thread *td)
{
TAILQ_INIT(&p->p_ksegrps); /* all ksegrps in proc */
TAILQ_INIT(&p->p_threads); /* all threads in proc */
TAILQ_INIT(&p->p_suspended); /* Threads suspended */
p->p_numksegrps = 0;
p->p_numthreads = 0;
ksegrp_link(kg, p);
kse_link(ke, kg);
thread_link(td, kg);
}
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/*
* Initialize global thread allocation resources.
*/
void
threadinit(void)
{
thread_zone = uma_zcreate("THREAD", sched_sizeof_thread(),
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thread_ctor, thread_dtor, thread_init, thread_fini,
UMA_ALIGN_CACHE, 0);
tid_zone = uma_zcreate("TID", sizeof(struct tid_bitmap_part),
NULL, NULL, NULL, NULL, UMA_ALIGN_CACHE, 0);
ksegrp_zone = uma_zcreate("KSEGRP", sched_sizeof_ksegrp(),
NULL, NULL, ksegrp_init, NULL,
UMA_ALIGN_CACHE, 0);
kse_zone = uma_zcreate("KSE", sched_sizeof_kse(),
NULL, NULL, kse_init, NULL,
UMA_ALIGN_CACHE, 0);
kseinit();
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}
/*
* Stash an embarasingly extra thread into the zombie thread queue.
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*/
void
thread_stash(struct thread *td)
{
mtx_lock_spin(&kse_zombie_lock);
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TAILQ_INSERT_HEAD(&zombie_threads, td, td_runq);
mtx_unlock_spin(&kse_zombie_lock);
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}
/*
* Stash an embarasingly extra kse into the zombie kse queue.
*/
void
kse_stash(struct kse *ke)
{
mtx_lock_spin(&kse_zombie_lock);
TAILQ_INSERT_HEAD(&zombie_kses, ke, ke_procq);
mtx_unlock_spin(&kse_zombie_lock);
}
/*
* Stash an embarasingly extra ksegrp into the zombie ksegrp queue.
*/
void
ksegrp_stash(struct ksegrp *kg)
{
mtx_lock_spin(&kse_zombie_lock);
TAILQ_INSERT_HEAD(&zombie_ksegrps, kg, kg_ksegrp);
mtx_unlock_spin(&kse_zombie_lock);
}
/*
* Reap zombie kse resource.
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*/
void
thread_reap(void)
{
struct thread *td_first, *td_next;
struct kse *ke_first, *ke_next;
struct ksegrp *kg_first, * kg_next;
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/*
* Don't even bother to lock if none at this instant,
* we really don't care about the next instant..
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*/
if ((!TAILQ_EMPTY(&zombie_threads))
|| (!TAILQ_EMPTY(&zombie_kses))
|| (!TAILQ_EMPTY(&zombie_ksegrps))) {
mtx_lock_spin(&kse_zombie_lock);
td_first = TAILQ_FIRST(&zombie_threads);
ke_first = TAILQ_FIRST(&zombie_kses);
kg_first = TAILQ_FIRST(&zombie_ksegrps);
if (td_first)
TAILQ_INIT(&zombie_threads);
if (ke_first)
TAILQ_INIT(&zombie_kses);
if (kg_first)
TAILQ_INIT(&zombie_ksegrps);
mtx_unlock_spin(&kse_zombie_lock);
while (td_first) {
td_next = TAILQ_NEXT(td_first, td_runq);
if (td_first->td_ucred)
crfree(td_first->td_ucred);
thread_free(td_first);
td_first = td_next;
}
while (ke_first) {
ke_next = TAILQ_NEXT(ke_first, ke_procq);
kse_free(ke_first);
ke_first = ke_next;
}
while (kg_first) {
kg_next = TAILQ_NEXT(kg_first, kg_ksegrp);
ksegrp_free(kg_first);
kg_first = kg_next;
}
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}
kse_GC();
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}
/*
* Allocate a ksegrp.
*/
struct ksegrp *
ksegrp_alloc(void)
{
return (uma_zalloc(ksegrp_zone, M_WAITOK));
}
/*
* Allocate a kse.
*/
struct kse *
kse_alloc(void)
{
return (uma_zalloc(kse_zone, M_WAITOK));
}
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/*
* Allocate a thread.
*/
struct thread *
thread_alloc(void)
{
thread_reap(); /* check if any zombies to get */
return (uma_zalloc(thread_zone, M_WAITOK));
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}
/*
* Deallocate a ksegrp.
*/
void
ksegrp_free(struct ksegrp *td)
{
uma_zfree(ksegrp_zone, td);
}
/*
* Deallocate a kse.
*/
void
kse_free(struct kse *td)
{
uma_zfree(kse_zone, td);
}
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/*
* Deallocate a thread.
*/
void
thread_free(struct thread *td)
{
cpu_thread_clean(td);
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uma_zfree(thread_zone, td);
}
/*
* Assign a thread ID.
*/
lwpid_t
thread_new_tid(void)
{
struct tid_bitmap_part *bmp, *new;
lwpid_t tid;
int bit, idx;
mtx_lock(&tid_lock);
STAILQ_FOREACH(bmp, &tid_bitmap, bmp_next) {
if (bmp->bmp_free)
break;
}
/* Create a new bitmap if we run out of free bits. */
if (bmp == NULL) {
mtx_unlock(&tid_lock);
new = uma_zalloc(tid_zone, M_WAITOK);
mtx_lock(&tid_lock);
bmp = STAILQ_LAST(&tid_bitmap, tid_bitmap_part, bmp_next);
if (bmp == NULL || bmp->bmp_free < TID_IDS_PER_PART/2) {
/* 1=free, 0=assigned. This way we can use ffsl(). */
memset(new->bmp_bitmap, ~0U, sizeof(new->bmp_bitmap));
new->bmp_base = (bmp == NULL) ? TID_MIN :
bmp->bmp_base + TID_IDS_PER_PART;
new->bmp_free = TID_IDS_PER_PART;
STAILQ_INSERT_TAIL(&tid_bitmap, new, bmp_next);
bmp = new;
new = NULL;
}
} else
new = NULL;
/* We have a bitmap with available IDs. */
idx = 0;
while (idx < TID_BITMAP_SIZE && bmp->bmp_bitmap[idx] == 0UL)
idx++;
bit = ffsl(bmp->bmp_bitmap[idx]) - 1;
tid = bmp->bmp_base + idx * TID_IDS_PER_IDX + bit;
bmp->bmp_bitmap[idx] &= ~(1UL << bit);
bmp->bmp_free--;
mtx_unlock(&tid_lock);
if (new != NULL)
uma_zfree(tid_zone, new);
return (tid);
}
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/*
* Discard the current thread and exit from its context.
2004-06-11 17:48:20 +00:00
* Always called with scheduler locked.
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*
* Because we can't free a thread while we're operating under its context,
* push the current thread into our CPU's deadthread holder. This means
* we needn't worry about someone else grabbing our context before we
2004-06-11 17:48:20 +00:00
* do a cpu_throw(). This may not be needed now as we are under schedlock.
* Maybe we can just do a thread_stash() as thr_exit1 does.
*/
/* XXX
* libthr expects its thread exit to return for the last
* thread, meaning that the program is back to non-threaded
* mode I guess. Because we do this (cpu_throw) unconditionally
* here, they have their own version of it. (thr_exit1())
* that doesn't do it all if this was the last thread.
* It is also called from thread_suspend_check().
* Of course in the end, they end up coming here through exit1
* anyhow.. After fixing 'thr' to play by the rules we should be able
* to merge these two functions together.
2002-06-29 07:04:59 +00:00
*/
void
thread_exit(void)
{
struct thread *td;
struct kse *ke;
struct proc *p;
struct ksegrp *kg;
td = curthread;
kg = td->td_ksegrp;
p = td->td_proc;
ke = td->td_kse;
mtx_assert(&sched_lock, MA_OWNED);
KASSERT(p != NULL, ("thread exiting without a process"));
KASSERT(ke != NULL, ("thread exiting without a kse"));
KASSERT(kg != NULL, ("thread exiting without a kse group"));
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PROC_LOCK_ASSERT(p, MA_OWNED);
CTR1(KTR_PROC, "thread_exit: thread %p", td);
mtx_assert(&Giant, MA_NOTOWNED);
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if (td->td_standin != NULL) {
thread_stash(td->td_standin);
td->td_standin = NULL;
}
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cpu_thread_exit(td); /* XXXSMP */
/*
* The last thread is left attached to the process
* So that the whole bundle gets recycled. Skip
* all this stuff.
*/
if (p->p_numthreads > 1) {
thread_unlink(td);
if (p->p_maxthrwaits)
wakeup(&p->p_numthreads);
/*
* The test below is NOT true if we are the
* sole exiting thread. P_STOPPED_SNGL is unset
* in exit1() after it is the only survivor.
*/
if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
if (p->p_numthreads == p->p_suspcount) {
thread_unsuspend_one(p->p_singlethread);
}
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}
/*
* Because each upcall structure has an owner thread,
* owner thread exits only when process is in exiting
* state, so upcall to userland is no longer needed,
* deleting upcall structure is safe here.
* So when all threads in a group is exited, all upcalls
* in the group should be automatically freed.
*/
if (td->td_upcall)
upcall_remove(td);
sched_exit_thread(FIRST_THREAD_IN_PROC(p), td);
sched_exit_kse(FIRST_KSE_IN_PROC(p), ke);
ke->ke_state = KES_UNQUEUED;
ke->ke_thread = NULL;
/*
* Decide what to do with the KSE attached to this thread.
*/
if (ke->ke_flags & KEF_EXIT) {
kse_unlink(ke);
if (kg->kg_kses == 0) {
sched_exit_ksegrp(FIRST_KSEGRP_IN_PROC(p), kg);
ksegrp_unlink(kg);
}
}
else
kse_reassign(ke);
PROC_UNLOCK(p);
td->td_kse = NULL;
td->td_state = TDS_INACTIVE;
#if 0
td->td_proc = NULL;
#endif
td->td_ksegrp = NULL;
td->td_last_kse = NULL;
PCPU_SET(deadthread, td);
} else {
PROC_UNLOCK(p);
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}
/* XXX Shouldn't cpu_throw() here. */
Commit a partial lazy thread switch mechanism for i386. it isn't as lazy as it could be and can do with some more cleanup. Currently its under options LAZY_SWITCH. What this does is avoid %cr3 reloads for short context switches that do not involve another user process. ie: we can take an interrupt, switch to a kthread and return to the user without explicitly flushing the tlb. However, this isn't as exciting as it could be, the interrupt overhead is still high and too much blocks on Giant still. There are some debug sysctls, for stats and for an on/off switch. The main problem with doing this has been "what if the process that you're running on exits while we're borrowing its address space?" - in this case we use an IPI to give it a kick when we're about to reclaim the pmap. Its not compiled in unless you add the LAZY_SWITCH option. I want to fix a few more things and get some more feedback before turning it on by default. This is NOT a replacement for Bosko's lazy interrupt stuff. This was more meant for the kthread case, while his was for interrupts. Mine helps a little for interrupts, but his helps a lot more. The stats are enabled with options SWTCH_OPTIM_STATS - this has been a pseudo-option for years, I just added a bunch of stuff to it. One non-trivial change was to select a new thread before calling cpu_switch() in the first place. This allows us to catch the silly case of doing a cpu_switch() to the current process. This happens uncomfortably often. This simplifies a bit of the asm code in cpu_switch (no longer have to call choosethread() in the middle). This has been implemented on i386 and (thanks to jake) sparc64. The others will come soon. This is actually seperate to the lazy switch stuff. Glanced at by: jake, jhb
2003-04-02 23:53:30 +00:00
mtx_assert(&sched_lock, MA_OWNED);
cpu_throw(td, choosethread());
panic("I'm a teapot!");
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/* NOTREACHED */
}
/*
* Do any thread specific cleanups that may be needed in wait()
* called with Giant, proc and schedlock not held.
*/
void
thread_wait(struct proc *p)
{
struct thread *td;
mtx_assert(&Giant, MA_NOTOWNED);
KASSERT((p->p_numthreads == 1), ("Multiple threads in wait1()"));
KASSERT((p->p_numksegrps == 1), ("Multiple ksegrps in wait1()"));
FOREACH_THREAD_IN_PROC(p, td) {
if (td->td_standin != NULL) {
thread_free(td->td_standin);
td->td_standin = NULL;
}
cpu_thread_clean(td);
}
thread_reap(); /* check for zombie threads etc. */
}
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/*
* Link a thread to a process.
* set up anything that needs to be initialized for it to
* be used by the process.
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*
* Note that we do not link to the proc's ucred here.
* The thread is linked as if running but no KSE assigned.
*/
void
thread_link(struct thread *td, struct ksegrp *kg)
{
struct proc *p;
p = kg->kg_proc;
td->td_state = TDS_INACTIVE;
td->td_proc = p;
td->td_ksegrp = kg;
td->td_last_kse = NULL;
td->td_flags = 0;
td->td_kflags = 0;
td->td_kse = NULL;
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LIST_INIT(&td->td_contested);
callout_init(&td->td_slpcallout, CALLOUT_MPSAFE);
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TAILQ_INSERT_HEAD(&p->p_threads, td, td_plist);
TAILQ_INSERT_HEAD(&kg->kg_threads, td, td_kglist);
p->p_numthreads++;
kg->kg_numthreads++;
}
void
thread_unlink(struct thread *td)
{
struct proc *p = td->td_proc;
struct ksegrp *kg = td->td_ksegrp;
mtx_assert(&sched_lock, MA_OWNED);
TAILQ_REMOVE(&p->p_threads, td, td_plist);
p->p_numthreads--;
TAILQ_REMOVE(&kg->kg_threads, td, td_kglist);
kg->kg_numthreads--;
/* could clear a few other things here */
}
/*
* Purge a ksegrp resource. When a ksegrp is preparing to
* exit, it calls this function.
*/
void
kse_purge_group(struct thread *td)
{
struct ksegrp *kg;
struct kse *ke;
kg = td->td_ksegrp;
KASSERT(kg->kg_numthreads == 1, ("%s: bad thread number", __func__));
while ((ke = TAILQ_FIRST(&kg->kg_iq)) != NULL) {
KASSERT(ke->ke_state == KES_IDLE,
("%s: wrong idle KSE state", __func__));
kse_unlink(ke);
}
KASSERT((kg->kg_kses == 1),
("%s: ksegrp still has %d KSEs", __func__, kg->kg_kses));
KASSERT((kg->kg_numupcalls == 0),
("%s: ksegrp still has %d upcall datas",
__func__, kg->kg_numupcalls));
}
/*
* Purge a process's KSE resource. When a process is preparing to
* exit, it calls kse_purge to release any extra KSE resources in
* the process.
*/
void
kse_purge(struct proc *p, struct thread *td)
{
struct ksegrp *kg;
struct kse *ke;
KASSERT(p->p_numthreads == 1, ("bad thread number"));
while ((kg = TAILQ_FIRST(&p->p_ksegrps)) != NULL) {
TAILQ_REMOVE(&p->p_ksegrps, kg, kg_ksegrp);
p->p_numksegrps--;
/*
* There is no ownership for KSE, after all threads
* in the group exited, it is possible that some KSEs
* were left in idle queue, gc them now.
*/
while ((ke = TAILQ_FIRST(&kg->kg_iq)) != NULL) {
KASSERT(ke->ke_state == KES_IDLE,
("%s: wrong idle KSE state", __func__));
TAILQ_REMOVE(&kg->kg_iq, ke, ke_kgrlist);
kg->kg_idle_kses--;
TAILQ_REMOVE(&kg->kg_kseq, ke, ke_kglist);
kg->kg_kses--;
kse_stash(ke);
}
KASSERT(((kg->kg_kses == 0) && (kg != td->td_ksegrp)) ||
((kg->kg_kses == 1) && (kg == td->td_ksegrp)),
("ksegrp has wrong kg_kses: %d", kg->kg_kses));
KASSERT((kg->kg_numupcalls == 0),
("%s: ksegrp still has %d upcall datas",
__func__, kg->kg_numupcalls));
if (kg != td->td_ksegrp)
ksegrp_stash(kg);
}
TAILQ_INSERT_HEAD(&p->p_ksegrps, td->td_ksegrp, kg_ksegrp);
p->p_numksegrps++;
}
2002-06-29 07:04:59 +00:00
/*
* Enforce single-threading.
*
* Returns 1 if the caller must abort (another thread is waiting to
* exit the process or similar). Process is locked!
* Returns 0 when you are successfully the only thread running.
* A process has successfully single threaded in the suspend mode when
* There are no threads in user mode. Threads in the kernel must be
* allowed to continue until they get to the user boundary. They may even
* copy out their return values and data before suspending. They may however be
* accellerated in reaching the user boundary as we will wake up
* any sleeping threads that are interruptable. (PCATCH).
*/
int
thread_single(int force_exit)
{
struct thread *td;
struct thread *td2;
struct proc *p;
int remaining;
2002-06-29 07:04:59 +00:00
td = curthread;
p = td->td_proc;
mtx_assert(&Giant, MA_NOTOWNED);
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PROC_LOCK_ASSERT(p, MA_OWNED);
KASSERT((td != NULL), ("curthread is NULL"));
if ((p->p_flag & P_SA) == 0 && p->p_numthreads == 1)
2002-06-29 07:04:59 +00:00
return (0);
/* Is someone already single threading? */
if (p->p_singlethread)
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return (1);
if (force_exit == SINGLE_EXIT) {
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p->p_flag |= P_SINGLE_EXIT;
} else
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p->p_flag &= ~P_SINGLE_EXIT;
p->p_flag |= P_STOPPED_SINGLE;
mtx_lock_spin(&sched_lock);
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p->p_singlethread = td;
if (force_exit == SINGLE_EXIT)
remaining = p->p_numthreads;
else
remaining = p->p_numthreads - p->p_suspcount;
while (remaining != 1) {
2002-06-29 07:04:59 +00:00
FOREACH_THREAD_IN_PROC(p, td2) {
if (td2 == td)
continue;
2003-04-19 04:39:10 +00:00
td2->td_flags |= TDF_ASTPENDING;
if (TD_IS_INHIBITED(td2)) {
if (force_exit == SINGLE_EXIT) {
if (TD_IS_SUSPENDED(td2)) {
thread_unsuspend_one(td2);
}
if (TD_ON_SLEEPQ(td2) &&
(td2->td_flags & TDF_SINTR)) {
Switch the sleep/wakeup and condition variable implementations to use the sleep queue interface: - Sleep queues attempt to merge some of the benefits of both sleep queues and condition variables. Having sleep qeueus in a hash table avoids having to allocate a queue head for each wait channel. Thus, struct cv has shrunk down to just a single char * pointer now. However, the hash table does not hold threads directly, but queue heads. This means that once you have located a queue in the hash bucket, you no longer have to walk the rest of the hash chain looking for threads. Instead, you have a list of all the threads sleeping on that wait channel. - Outside of the sleepq code and the sleep/cv code the kernel no longer differentiates between cv's and sleep/wakeup. For example, calls to abortsleep() and cv_abort() are replaced with a call to sleepq_abort(). Thus, the TDF_CVWAITQ flag is removed. Also, calls to unsleep() and cv_waitq_remove() have been replaced with calls to sleepq_remove(). - The sched_sleep() function no longer accepts a priority argument as sleep's no longer inherently bump the priority. Instead, this is soley a propery of msleep() which explicitly calls sched_prio() before blocking. - The TDF_ONSLEEPQ flag has been dropped as it was never used. The associated TDF_SET_ONSLEEPQ and TDF_CLR_ON_SLEEPQ macros have also been dropped and replaced with a single explicit clearing of td_wchan. TD_SET_ONSLEEPQ() would really have only made sense if it had taken the wait channel and message as arguments anyway. Now that that only happens in one place, a macro would be overkill.
2004-02-27 18:52:44 +00:00
sleepq_abort(td2);
}
} else {
if (TD_IS_SUSPENDED(td2))
continue;
/*
* maybe other inhibitted states too?
* XXXKSE Is it totally safe to
* suspend a non-interruptable thread?
*/
if (td2->td_inhibitors &
(TDI_SLEEPING | TDI_SWAPPED))
thread_suspend_one(td2);
}
2002-06-29 07:04:59 +00:00
}
}
if (force_exit == SINGLE_EXIT)
remaining = p->p_numthreads;
else
remaining = p->p_numthreads - p->p_suspcount;
/*
* Maybe we suspended some threads.. was it enough?
*/
if (remaining == 1)
break;
2002-06-29 07:04:59 +00:00
/*
* Wake us up when everyone else has suspended.
* In the mean time we suspend as well.
2002-06-29 07:04:59 +00:00
*/
thread_suspend_one(td);
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PROC_UNLOCK(p);
mi_switch(SW_VOL);
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mtx_unlock_spin(&sched_lock);
PROC_LOCK(p);
mtx_lock_spin(&sched_lock);
if (force_exit == SINGLE_EXIT)
remaining = p->p_numthreads;
else
remaining = p->p_numthreads - p->p_suspcount;
2002-06-29 07:04:59 +00:00
}
if (force_exit == SINGLE_EXIT) {
if (td->td_upcall)
upcall_remove(td);
kse_purge(p, td);
}
mtx_unlock_spin(&sched_lock);
2002-06-29 07:04:59 +00:00
return (0);
}
/*
* Called in from locations that can safely check to see
* whether we have to suspend or at least throttle for a
* single-thread event (e.g. fork).
*
* Such locations include userret().
* If the "return_instead" argument is non zero, the thread must be able to
* accept 0 (caller may continue), or 1 (caller must abort) as a result.
*
* The 'return_instead' argument tells the function if it may do a
* thread_exit() or suspend, or whether the caller must abort and back
* out instead.
*
* If the thread that set the single_threading request has set the
* P_SINGLE_EXIT bit in the process flags then this call will never return
* if 'return_instead' is false, but will exit.
*
* P_SINGLE_EXIT | return_instead == 0| return_instead != 0
*---------------+--------------------+---------------------
* 0 | returns 0 | returns 0 or 1
* | when ST ends | immediatly
*---------------+--------------------+---------------------
* 1 | thread exits | returns 1
* | | immediatly
* 0 = thread_exit() or suspension ok,
* other = return error instead of stopping the thread.
*
* While a full suspension is under effect, even a single threading
* thread would be suspended if it made this call (but it shouldn't).
* This call should only be made from places where
* thread_exit() would be safe as that may be the outcome unless
2002-06-29 07:04:59 +00:00
* return_instead is set.
*/
int
thread_suspend_check(int return_instead)
{
struct thread *td;
struct proc *p;
2002-06-29 07:04:59 +00:00
td = curthread;
p = td->td_proc;
mtx_assert(&Giant, MA_NOTOWNED);
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PROC_LOCK_ASSERT(p, MA_OWNED);
while (P_SHOULDSTOP(p)) {
if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
2002-06-29 07:04:59 +00:00
KASSERT(p->p_singlethread != NULL,
("singlethread not set"));
/*
* The only suspension in action is a
* single-threading. Single threader need not stop.
* XXX Should be safe to access unlocked
* as it can only be set to be true by us.
2002-06-29 07:04:59 +00:00
*/
if (p->p_singlethread == td)
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return (0); /* Exempt from stopping. */
}
if (return_instead)
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return (1);
mtx_lock_spin(&sched_lock);
thread_stopped(p);
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/*
* If the process is waiting for us to exit,
* this thread should just suicide.
* Assumes that P_SINGLE_EXIT implies P_STOPPED_SINGLE.
2002-06-29 07:04:59 +00:00
*/
if ((p->p_flag & P_SINGLE_EXIT) && (p->p_singlethread != td)) {
if (p->p_flag & P_SA)
thread_exit();
else
thr_exit1();
2002-06-29 07:04:59 +00:00
}
/*
* When a thread suspends, it just
* moves to the processes's suspend queue
* and stays there.
*/
thread_suspend_one(td);
if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
if (p->p_numthreads == p->p_suspcount) {
thread_unsuspend_one(p->p_singlethread);
}
}
PROC_UNLOCK(p);
mi_switch(SW_INVOL);
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mtx_unlock_spin(&sched_lock);
PROC_LOCK(p);
}
return (0);
}
In the kernel code, we have the tsleep() call with the PCATCH argument. PCATCH means 'if we get a signal, interrupt me!" and tsleep returns either EINTR or ERESTART depending on the circumstances. ERESTART is "special" because it causes the system call to fail, but right as it returns back to userland it tells the trap handler to move %eip back a bit so that userland will immediately re-run the syscall. This is a syscall restart. It only works for things like read() etc where nothing has changed yet. Note that *userland* is tricked into restarting the syscall by the kernel. The kernel doesn't actually do the restart. It is deadly for things like select, poll, nanosleep etc where it might cause the elapsed time to be reset and start again from scratch. So those syscalls do this to prevent userland rerunning the syscall: if (error == ERESTART) error = EINTR; Fake "signals" like SIGTSTP from ^Z etc do not normally invoke userland signal handlers. But, in -current, the PCATCH *is* being triggered and tsleep is returning ERESTART, and the syscall is aborted even though no userland signal handler was run. That is the fault here. We're triggering the PCATCH in cases that we shouldn't. ie: it is being triggered on *any* signal processing, rather than the case where the signal is posted to userland. --- Peter The work of psignal() is a patchwork of special case required by the process debugging and job-control facilities... --- Kirk McKusick "The design and impelementation of the 4.4BSD Operating system" Page 105 in STABLE source, when psignal is posting a STOP signal to sleeping process and the signal action of the process is SIG_DFL, system will directly change the process state from SSLEEP to SSTOP, and when SIGCONT is posted to the stopped process, if it finds that the process is still on sleep queue, the process state will be restored to SSLEEP, and won't wakeup the process. this commit mimics the behaviour in STABLE source tree. Reviewed by: Jon Mini, Tim Robbins, Peter Wemm Approved by: julian@freebsd.org (mentor)
2002-09-03 12:56:01 +00:00
void
thread_suspend_one(struct thread *td)
{
struct proc *p = td->td_proc;
mtx_assert(&sched_lock, MA_OWNED);
PROC_LOCK_ASSERT(p, MA_OWNED);
KASSERT(!TD_IS_SUSPENDED(td), ("already suspended"));
In the kernel code, we have the tsleep() call with the PCATCH argument. PCATCH means 'if we get a signal, interrupt me!" and tsleep returns either EINTR or ERESTART depending on the circumstances. ERESTART is "special" because it causes the system call to fail, but right as it returns back to userland it tells the trap handler to move %eip back a bit so that userland will immediately re-run the syscall. This is a syscall restart. It only works for things like read() etc where nothing has changed yet. Note that *userland* is tricked into restarting the syscall by the kernel. The kernel doesn't actually do the restart. It is deadly for things like select, poll, nanosleep etc where it might cause the elapsed time to be reset and start again from scratch. So those syscalls do this to prevent userland rerunning the syscall: if (error == ERESTART) error = EINTR; Fake "signals" like SIGTSTP from ^Z etc do not normally invoke userland signal handlers. But, in -current, the PCATCH *is* being triggered and tsleep is returning ERESTART, and the syscall is aborted even though no userland signal handler was run. That is the fault here. We're triggering the PCATCH in cases that we shouldn't. ie: it is being triggered on *any* signal processing, rather than the case where the signal is posted to userland. --- Peter The work of psignal() is a patchwork of special case required by the process debugging and job-control facilities... --- Kirk McKusick "The design and impelementation of the 4.4BSD Operating system" Page 105 in STABLE source, when psignal is posting a STOP signal to sleeping process and the signal action of the process is SIG_DFL, system will directly change the process state from SSLEEP to SSTOP, and when SIGCONT is posted to the stopped process, if it finds that the process is still on sleep queue, the process state will be restored to SSLEEP, and won't wakeup the process. this commit mimics the behaviour in STABLE source tree. Reviewed by: Jon Mini, Tim Robbins, Peter Wemm Approved by: julian@freebsd.org (mentor)
2002-09-03 12:56:01 +00:00
p->p_suspcount++;
TD_SET_SUSPENDED(td);
In the kernel code, we have the tsleep() call with the PCATCH argument. PCATCH means 'if we get a signal, interrupt me!" and tsleep returns either EINTR or ERESTART depending on the circumstances. ERESTART is "special" because it causes the system call to fail, but right as it returns back to userland it tells the trap handler to move %eip back a bit so that userland will immediately re-run the syscall. This is a syscall restart. It only works for things like read() etc where nothing has changed yet. Note that *userland* is tricked into restarting the syscall by the kernel. The kernel doesn't actually do the restart. It is deadly for things like select, poll, nanosleep etc where it might cause the elapsed time to be reset and start again from scratch. So those syscalls do this to prevent userland rerunning the syscall: if (error == ERESTART) error = EINTR; Fake "signals" like SIGTSTP from ^Z etc do not normally invoke userland signal handlers. But, in -current, the PCATCH *is* being triggered and tsleep is returning ERESTART, and the syscall is aborted even though no userland signal handler was run. That is the fault here. We're triggering the PCATCH in cases that we shouldn't. ie: it is being triggered on *any* signal processing, rather than the case where the signal is posted to userland. --- Peter The work of psignal() is a patchwork of special case required by the process debugging and job-control facilities... --- Kirk McKusick "The design and impelementation of the 4.4BSD Operating system" Page 105 in STABLE source, when psignal is posting a STOP signal to sleeping process and the signal action of the process is SIG_DFL, system will directly change the process state from SSLEEP to SSTOP, and when SIGCONT is posted to the stopped process, if it finds that the process is still on sleep queue, the process state will be restored to SSLEEP, and won't wakeup the process. this commit mimics the behaviour in STABLE source tree. Reviewed by: Jon Mini, Tim Robbins, Peter Wemm Approved by: julian@freebsd.org (mentor)
2002-09-03 12:56:01 +00:00
TAILQ_INSERT_TAIL(&p->p_suspended, td, td_runq);
/*
* Hack: If we are suspending but are on the sleep queue
* then we are in msleep or the cv equivalent. We
* want to look like we have two Inhibitors.
* May already be set.. doesn't matter.
*/
if (TD_ON_SLEEPQ(td))
TD_SET_SLEEPING(td);
In the kernel code, we have the tsleep() call with the PCATCH argument. PCATCH means 'if we get a signal, interrupt me!" and tsleep returns either EINTR or ERESTART depending on the circumstances. ERESTART is "special" because it causes the system call to fail, but right as it returns back to userland it tells the trap handler to move %eip back a bit so that userland will immediately re-run the syscall. This is a syscall restart. It only works for things like read() etc where nothing has changed yet. Note that *userland* is tricked into restarting the syscall by the kernel. The kernel doesn't actually do the restart. It is deadly for things like select, poll, nanosleep etc where it might cause the elapsed time to be reset and start again from scratch. So those syscalls do this to prevent userland rerunning the syscall: if (error == ERESTART) error = EINTR; Fake "signals" like SIGTSTP from ^Z etc do not normally invoke userland signal handlers. But, in -current, the PCATCH *is* being triggered and tsleep is returning ERESTART, and the syscall is aborted even though no userland signal handler was run. That is the fault here. We're triggering the PCATCH in cases that we shouldn't. ie: it is being triggered on *any* signal processing, rather than the case where the signal is posted to userland. --- Peter The work of psignal() is a patchwork of special case required by the process debugging and job-control facilities... --- Kirk McKusick "The design and impelementation of the 4.4BSD Operating system" Page 105 in STABLE source, when psignal is posting a STOP signal to sleeping process and the signal action of the process is SIG_DFL, system will directly change the process state from SSLEEP to SSTOP, and when SIGCONT is posted to the stopped process, if it finds that the process is still on sleep queue, the process state will be restored to SSLEEP, and won't wakeup the process. this commit mimics the behaviour in STABLE source tree. Reviewed by: Jon Mini, Tim Robbins, Peter Wemm Approved by: julian@freebsd.org (mentor)
2002-09-03 12:56:01 +00:00
}
void
thread_unsuspend_one(struct thread *td)
{
struct proc *p = td->td_proc;
mtx_assert(&sched_lock, MA_OWNED);
PROC_LOCK_ASSERT(p, MA_OWNED);
In the kernel code, we have the tsleep() call with the PCATCH argument. PCATCH means 'if we get a signal, interrupt me!" and tsleep returns either EINTR or ERESTART depending on the circumstances. ERESTART is "special" because it causes the system call to fail, but right as it returns back to userland it tells the trap handler to move %eip back a bit so that userland will immediately re-run the syscall. This is a syscall restart. It only works for things like read() etc where nothing has changed yet. Note that *userland* is tricked into restarting the syscall by the kernel. The kernel doesn't actually do the restart. It is deadly for things like select, poll, nanosleep etc where it might cause the elapsed time to be reset and start again from scratch. So those syscalls do this to prevent userland rerunning the syscall: if (error == ERESTART) error = EINTR; Fake "signals" like SIGTSTP from ^Z etc do not normally invoke userland signal handlers. But, in -current, the PCATCH *is* being triggered and tsleep is returning ERESTART, and the syscall is aborted even though no userland signal handler was run. That is the fault here. We're triggering the PCATCH in cases that we shouldn't. ie: it is being triggered on *any* signal processing, rather than the case where the signal is posted to userland. --- Peter The work of psignal() is a patchwork of special case required by the process debugging and job-control facilities... --- Kirk McKusick "The design and impelementation of the 4.4BSD Operating system" Page 105 in STABLE source, when psignal is posting a STOP signal to sleeping process and the signal action of the process is SIG_DFL, system will directly change the process state from SSLEEP to SSTOP, and when SIGCONT is posted to the stopped process, if it finds that the process is still on sleep queue, the process state will be restored to SSLEEP, and won't wakeup the process. this commit mimics the behaviour in STABLE source tree. Reviewed by: Jon Mini, Tim Robbins, Peter Wemm Approved by: julian@freebsd.org (mentor)
2002-09-03 12:56:01 +00:00
TAILQ_REMOVE(&p->p_suspended, td, td_runq);
TD_CLR_SUSPENDED(td);
In the kernel code, we have the tsleep() call with the PCATCH argument. PCATCH means 'if we get a signal, interrupt me!" and tsleep returns either EINTR or ERESTART depending on the circumstances. ERESTART is "special" because it causes the system call to fail, but right as it returns back to userland it tells the trap handler to move %eip back a bit so that userland will immediately re-run the syscall. This is a syscall restart. It only works for things like read() etc where nothing has changed yet. Note that *userland* is tricked into restarting the syscall by the kernel. The kernel doesn't actually do the restart. It is deadly for things like select, poll, nanosleep etc where it might cause the elapsed time to be reset and start again from scratch. So those syscalls do this to prevent userland rerunning the syscall: if (error == ERESTART) error = EINTR; Fake "signals" like SIGTSTP from ^Z etc do not normally invoke userland signal handlers. But, in -current, the PCATCH *is* being triggered and tsleep is returning ERESTART, and the syscall is aborted even though no userland signal handler was run. That is the fault here. We're triggering the PCATCH in cases that we shouldn't. ie: it is being triggered on *any* signal processing, rather than the case where the signal is posted to userland. --- Peter The work of psignal() is a patchwork of special case required by the process debugging and job-control facilities... --- Kirk McKusick "The design and impelementation of the 4.4BSD Operating system" Page 105 in STABLE source, when psignal is posting a STOP signal to sleeping process and the signal action of the process is SIG_DFL, system will directly change the process state from SSLEEP to SSTOP, and when SIGCONT is posted to the stopped process, if it finds that the process is still on sleep queue, the process state will be restored to SSLEEP, and won't wakeup the process. this commit mimics the behaviour in STABLE source tree. Reviewed by: Jon Mini, Tim Robbins, Peter Wemm Approved by: julian@freebsd.org (mentor)
2002-09-03 12:56:01 +00:00
p->p_suspcount--;
setrunnable(td);
In the kernel code, we have the tsleep() call with the PCATCH argument. PCATCH means 'if we get a signal, interrupt me!" and tsleep returns either EINTR or ERESTART depending on the circumstances. ERESTART is "special" because it causes the system call to fail, but right as it returns back to userland it tells the trap handler to move %eip back a bit so that userland will immediately re-run the syscall. This is a syscall restart. It only works for things like read() etc where nothing has changed yet. Note that *userland* is tricked into restarting the syscall by the kernel. The kernel doesn't actually do the restart. It is deadly for things like select, poll, nanosleep etc where it might cause the elapsed time to be reset and start again from scratch. So those syscalls do this to prevent userland rerunning the syscall: if (error == ERESTART) error = EINTR; Fake "signals" like SIGTSTP from ^Z etc do not normally invoke userland signal handlers. But, in -current, the PCATCH *is* being triggered and tsleep is returning ERESTART, and the syscall is aborted even though no userland signal handler was run. That is the fault here. We're triggering the PCATCH in cases that we shouldn't. ie: it is being triggered on *any* signal processing, rather than the case where the signal is posted to userland. --- Peter The work of psignal() is a patchwork of special case required by the process debugging and job-control facilities... --- Kirk McKusick "The design and impelementation of the 4.4BSD Operating system" Page 105 in STABLE source, when psignal is posting a STOP signal to sleeping process and the signal action of the process is SIG_DFL, system will directly change the process state from SSLEEP to SSTOP, and when SIGCONT is posted to the stopped process, if it finds that the process is still on sleep queue, the process state will be restored to SSLEEP, and won't wakeup the process. this commit mimics the behaviour in STABLE source tree. Reviewed by: Jon Mini, Tim Robbins, Peter Wemm Approved by: julian@freebsd.org (mentor)
2002-09-03 12:56:01 +00:00
}
2002-06-29 07:04:59 +00:00
/*
* Allow all threads blocked by single threading to continue running.
*/
void
thread_unsuspend(struct proc *p)
{
struct thread *td;
mtx_assert(&sched_lock, MA_OWNED);
2002-06-29 07:04:59 +00:00
PROC_LOCK_ASSERT(p, MA_OWNED);
if (!P_SHOULDSTOP(p)) {
while (( td = TAILQ_FIRST(&p->p_suspended))) {
In the kernel code, we have the tsleep() call with the PCATCH argument. PCATCH means 'if we get a signal, interrupt me!" and tsleep returns either EINTR or ERESTART depending on the circumstances. ERESTART is "special" because it causes the system call to fail, but right as it returns back to userland it tells the trap handler to move %eip back a bit so that userland will immediately re-run the syscall. This is a syscall restart. It only works for things like read() etc where nothing has changed yet. Note that *userland* is tricked into restarting the syscall by the kernel. The kernel doesn't actually do the restart. It is deadly for things like select, poll, nanosleep etc where it might cause the elapsed time to be reset and start again from scratch. So those syscalls do this to prevent userland rerunning the syscall: if (error == ERESTART) error = EINTR; Fake "signals" like SIGTSTP from ^Z etc do not normally invoke userland signal handlers. But, in -current, the PCATCH *is* being triggered and tsleep is returning ERESTART, and the syscall is aborted even though no userland signal handler was run. That is the fault here. We're triggering the PCATCH in cases that we shouldn't. ie: it is being triggered on *any* signal processing, rather than the case where the signal is posted to userland. --- Peter The work of psignal() is a patchwork of special case required by the process debugging and job-control facilities... --- Kirk McKusick "The design and impelementation of the 4.4BSD Operating system" Page 105 in STABLE source, when psignal is posting a STOP signal to sleeping process and the signal action of the process is SIG_DFL, system will directly change the process state from SSLEEP to SSTOP, and when SIGCONT is posted to the stopped process, if it finds that the process is still on sleep queue, the process state will be restored to SSLEEP, and won't wakeup the process. this commit mimics the behaviour in STABLE source tree. Reviewed by: Jon Mini, Tim Robbins, Peter Wemm Approved by: julian@freebsd.org (mentor)
2002-09-03 12:56:01 +00:00
thread_unsuspend_one(td);
2002-06-29 07:04:59 +00:00
}
} else if ((P_SHOULDSTOP(p) == P_STOPPED_SINGLE) &&
2002-06-29 07:04:59 +00:00
(p->p_numthreads == p->p_suspcount)) {
/*
* Stopping everything also did the job for the single
* threading request. Now we've downgraded to single-threaded,
* let it continue.
*/
In the kernel code, we have the tsleep() call with the PCATCH argument. PCATCH means 'if we get a signal, interrupt me!" and tsleep returns either EINTR or ERESTART depending on the circumstances. ERESTART is "special" because it causes the system call to fail, but right as it returns back to userland it tells the trap handler to move %eip back a bit so that userland will immediately re-run the syscall. This is a syscall restart. It only works for things like read() etc where nothing has changed yet. Note that *userland* is tricked into restarting the syscall by the kernel. The kernel doesn't actually do the restart. It is deadly for things like select, poll, nanosleep etc where it might cause the elapsed time to be reset and start again from scratch. So those syscalls do this to prevent userland rerunning the syscall: if (error == ERESTART) error = EINTR; Fake "signals" like SIGTSTP from ^Z etc do not normally invoke userland signal handlers. But, in -current, the PCATCH *is* being triggered and tsleep is returning ERESTART, and the syscall is aborted even though no userland signal handler was run. That is the fault here. We're triggering the PCATCH in cases that we shouldn't. ie: it is being triggered on *any* signal processing, rather than the case where the signal is posted to userland. --- Peter The work of psignal() is a patchwork of special case required by the process debugging and job-control facilities... --- Kirk McKusick "The design and impelementation of the 4.4BSD Operating system" Page 105 in STABLE source, when psignal is posting a STOP signal to sleeping process and the signal action of the process is SIG_DFL, system will directly change the process state from SSLEEP to SSTOP, and when SIGCONT is posted to the stopped process, if it finds that the process is still on sleep queue, the process state will be restored to SSLEEP, and won't wakeup the process. this commit mimics the behaviour in STABLE source tree. Reviewed by: Jon Mini, Tim Robbins, Peter Wemm Approved by: julian@freebsd.org (mentor)
2002-09-03 12:56:01 +00:00
thread_unsuspend_one(p->p_singlethread);
2002-06-29 07:04:59 +00:00
}
}
void
thread_single_end(void)
{
struct thread *td;
struct proc *p;
td = curthread;
p = td->td_proc;
PROC_LOCK_ASSERT(p, MA_OWNED);
p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT);
mtx_lock_spin(&sched_lock);
2002-06-29 07:04:59 +00:00
p->p_singlethread = NULL;
/*
* If there are other threads they mey now run,
* unless of course there is a blanket 'stop order'
* on the process. The single threader must be allowed
* to continue however as this is a bad place to stop.
*/
if ((p->p_numthreads != 1) && (!P_SHOULDSTOP(p))) {
while (( td = TAILQ_FIRST(&p->p_suspended))) {
thread_unsuspend_one(td);
}
}
mtx_unlock_spin(&sched_lock);
2002-06-29 07:04:59 +00:00
}