- When signalling waiters, try not to awaken them immediatley. If we hold
the mutex that the waiters are using to synchronise, then transfer them to the mutex's waiters list so that the wakeup is deferred until release of the mutex. Improves the timings for CV sleep/wakeup by between 30-100% in tests conducted locally on a UP system. There can be a penalty for MP systems when only one thread is being awoken, but in practice I think it won't be be an issue. - pthread_signal: search for a thread that does not have a pending wakeup. Threads can have a pending wakeup and still be on the waiters list if we clash with an earlier pthread_cond_broadcast().
This commit is contained in:
ad
parent
b0427b61fb
commit
d68cf1be1a
|
|
@ -1,4 +1,4 @@
|
|||
/* $NetBSD: pthread_cond.c,v 1.27 2007/03/14 23:34:48 ad Exp $ */
|
||||
/* $NetBSD: pthread_cond.c,v 1.28 2007/03/20 23:49:58 ad Exp $ */
|
||||
|
||||
/*-
|
||||
* Copyright (c) 2001, 2006, 2007 The NetBSD Foundation, Inc.
|
||||
|
|
@ -37,7 +37,7 @@
|
|||
*/
|
||||
|
||||
#include <sys/cdefs.h>
|
||||
__RCSID("$NetBSD: pthread_cond.c,v 1.27 2007/03/14 23:34:48 ad Exp $");
|
||||
__RCSID("$NetBSD: pthread_cond.c,v 1.28 2007/03/20 23:49:58 ad Exp $");
|
||||
|
||||
#include <errno.h>
|
||||
#include <sys/time.h>
|
||||
|
|
@ -121,24 +121,23 @@ pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
|
|||
if (__predict_false(self->pt_cancel))
|
||||
pthread_exit(PTHREAD_CANCELED);
|
||||
pthread_spinlock(self, &cond->ptc_lock);
|
||||
#ifdef ERRORCHECK
|
||||
if (cond->ptc_mutex == NULL)
|
||||
cond->ptc_mutex = mutex;
|
||||
else
|
||||
else {
|
||||
#ifdef ERRORCHECK
|
||||
pthread__error(EINVAL,
|
||||
"Multiple mutexes used for condition wait",
|
||||
cond->ptc_mutex == mutex);
|
||||
#endif
|
||||
}
|
||||
PTQ_INSERT_HEAD(&cond->ptc_waiters, self, pt_sleep);
|
||||
self->pt_sleeponq = 1;
|
||||
self->pt_sleepobj = &cond->ptc_waiters;
|
||||
pthread_mutex_unlock(mutex);
|
||||
(void)pthread__park(self, &cond->ptc_lock, &cond->ptc_waiters,
|
||||
NULL, 1);
|
||||
#ifdef ERRORCHECK
|
||||
if (PTQ_EMPTY(&cond->ptc_waiters))
|
||||
cond->ptc_mutex = NULL;
|
||||
#endif
|
||||
pthread_spinunlock(self, &cond->ptc_lock);
|
||||
pthread_mutex_lock(mutex);
|
||||
|
||||
|
|
@ -181,24 +180,23 @@ pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
|
|||
if (__predict_false(self->pt_cancel))
|
||||
pthread_exit(PTHREAD_CANCELED);
|
||||
pthread_spinlock(self, &cond->ptc_lock);
|
||||
#ifdef ERRORCHECK
|
||||
if (cond->ptc_mutex == NULL)
|
||||
cond->ptc_mutex = mutex;
|
||||
else
|
||||
else {
|
||||
#ifdef ERRORCHECK
|
||||
pthread__error(EINVAL,
|
||||
"Multiple mutexes used for condition wait",
|
||||
cond->ptc_mutex == mutex);
|
||||
#endif
|
||||
}
|
||||
PTQ_INSERT_HEAD(&cond->ptc_waiters, self, pt_sleep);
|
||||
self->pt_sleeponq = 1;
|
||||
self->pt_sleepobj = &cond->ptc_waiters;
|
||||
pthread_mutex_unlock(mutex);
|
||||
retval = pthread__park(self, &cond->ptc_lock, &cond->ptc_waiters,
|
||||
abstime, 1);
|
||||
#ifdef ERRORCHECK
|
||||
if (PTQ_EMPTY(&cond->ptc_waiters))
|
||||
cond->ptc_mutex = NULL;
|
||||
#endif
|
||||
pthread_spinunlock(self, &cond->ptc_lock);
|
||||
|
||||
SDPRINTF(("(cond timed wait %p) Woke up on %p, mutex %p\n",
|
||||
|
|
@ -216,6 +214,7 @@ int
|
|||
pthread_cond_signal(pthread_cond_t *cond)
|
||||
{
|
||||
pthread_t self, signaled;
|
||||
pthread_mutex_t *mutex;
|
||||
|
||||
pthread__error(EINVAL, "Invalid condition variable",
|
||||
cond->ptc_magic == _PT_COND_MAGIC);
|
||||
|
|
@ -229,18 +228,48 @@ pthread_cond_signal(pthread_cond_t *cond)
|
|||
|
||||
self = pthread__self();
|
||||
pthread_spinlock(self, &cond->ptc_lock);
|
||||
signaled = PTQ_FIRST(&cond->ptc_waiters);
|
||||
if (signaled != NULL) {
|
||||
PTQ_REMOVE(&cond->ptc_waiters, signaled, pt_sleep);
|
||||
if (PTQ_EMPTY(&cond->ptc_waiters))
|
||||
cond->ptc_mutex = NULL;
|
||||
|
||||
/*
|
||||
* Find a thread that is still blocked (no pending wakeup).
|
||||
* A wakeup can be pending if we have interrupted unpark_all
|
||||
* as it releases the interlock.
|
||||
*/
|
||||
PTQ_FOREACH(signaled, &cond->ptc_waiters, pt_sleep) {
|
||||
if (signaled->pt_sleepobj != NULL)
|
||||
break;
|
||||
}
|
||||
if (__predict_false(signaled == NULL)) {
|
||||
cond->ptc_mutex = NULL;
|
||||
pthread_spinunlock(self, &cond->ptc_lock);
|
||||
return 0;
|
||||
}
|
||||
|
||||
/*
|
||||
* Pull the thread off the queue.
|
||||
*/
|
||||
PTQ_REMOVE(&cond->ptc_waiters, signaled, pt_sleep);
|
||||
mutex = cond->ptc_mutex;
|
||||
if (PTQ_EMPTY(&cond->ptc_waiters))
|
||||
cond->ptc_mutex = NULL;
|
||||
|
||||
/*
|
||||
* For all valid uses of pthread_cond_signal(), the caller will
|
||||
* hold the mutex that the target is using to synchronize with.
|
||||
* To avoid the target awakening and immediatley blocking on the
|
||||
* mutex, transfer the thread to be awoken to the mutex's waiters
|
||||
* list. The waiter will be set running when the caller (this
|
||||
* thread) releases the mutex.
|
||||
*/
|
||||
if (self->pt_mutexhint != NULL && self->pt_mutexhint == mutex) {
|
||||
pthread_spinunlock(self, &cond->ptc_lock);
|
||||
pthread_spinlock(self, &mutex->ptm_interlock);
|
||||
PTQ_INSERT_HEAD(&mutex->ptm_blocked, signaled, pt_sleep);
|
||||
pthread_spinunlock(self, &mutex->ptm_interlock);
|
||||
} else {
|
||||
pthread__unpark(self, &cond->ptc_lock,
|
||||
&cond->ptc_waiters, signaled);
|
||||
PTHREADD_ADD(PTHREADD_COND_WOKEUP);
|
||||
return 0;
|
||||
}
|
||||
cond->ptc_mutex = NULL;
|
||||
pthread_spinunlock(self, &cond->ptc_lock);
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
|
@ -249,9 +278,11 @@ pthread_cond_signal(pthread_cond_t *cond)
|
|||
int
|
||||
pthread_cond_broadcast(pthread_cond_t *cond)
|
||||
{
|
||||
pthread_t self;
|
||||
pthread_t self, signaled, next;
|
||||
pthread_mutex_t *mutex;
|
||||
|
||||
pthread__error(EINVAL, "Invalid condition variable", cond->ptc_magic == _PT_COND_MAGIC);
|
||||
pthread__error(EINVAL, "Invalid condition variable",
|
||||
cond->ptc_magic == _PT_COND_MAGIC);
|
||||
|
||||
PTHREADD_ADD(PTHREADD_COND_BROADCAST);
|
||||
SDPRINTF(("(cond signal %p) Broadcasting %p\n",
|
||||
|
|
@ -262,8 +293,31 @@ pthread_cond_broadcast(pthread_cond_t *cond)
|
|||
|
||||
self = pthread__self();
|
||||
pthread_spinlock(self, &cond->ptc_lock);
|
||||
mutex = cond->ptc_mutex;
|
||||
cond->ptc_mutex = NULL;
|
||||
pthread__unpark_all(self, &cond->ptc_lock, &cond->ptc_waiters);
|
||||
|
||||
/*
|
||||
* Try to transfer waiters to the mutex's waiters list (see
|
||||
* pthread_cond_signal()). Only transfer waiters for which
|
||||
* there is no pending wakeup.
|
||||
*/
|
||||
if (self->pt_mutexhint != NULL && self->pt_mutexhint == mutex) {
|
||||
pthread_spinlock(self, &mutex->ptm_interlock);
|
||||
for (signaled = PTQ_FIRST(&cond->ptc_waiters);
|
||||
signaled != NULL;
|
||||
signaled = next) {
|
||||
next = PTQ_NEXT(signaled, pt_sleep);
|
||||
if (__predict_false(signaled->pt_sleepobj == NULL))
|
||||
continue;
|
||||
PTQ_REMOVE(&cond->ptc_waiters, signaled, pt_sleep);
|
||||
PTQ_INSERT_HEAD(&mutex->ptm_blocked, signaled,
|
||||
pt_sleep);
|
||||
}
|
||||
pthread_spinunlock(self, &mutex->ptm_interlock);
|
||||
pthread_spinunlock(self, &cond->ptc_lock);
|
||||
} else
|
||||
pthread__unpark_all(self, &cond->ptc_lock, &cond->ptc_waiters);
|
||||
|
||||
PTHREADD_ADD(PTHREADD_COND_WOKEUP);
|
||||
|
||||
return 0;
|
||||
|
|
|
|||
Loading…
Reference in New Issue