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Add a per-mutex deferred wakeup flag so that threads doing something like

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the following do not wake other threads early:

	pthread_mutex_lock(&mutex);
	pthread_cond_broadcast(&cond);
	foo = malloc(100);		/* takes libc mutexes */
	pthread_mutex_unlock(&mutex);
This commit is contained in:
ad 2007-09-13 23:51:47 +00:00
parent aff14ee9c8
commit 20e3392edc
4 changed files with 35 additions and 22 deletions
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10
lib/libpthread/pthread_cond.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: pthread_cond.c,v 1.36 2007/09/08 22:49:50 ad Exp $ */
/* $NetBSD: pthread_cond.c,v 1.37 2007/09/13 23:51:47 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 1.36 2007/09/08 22:49:50 ad Exp $");
__RCSID("$NetBSD: pthread_cond.c,v 1.37 2007/09/13 23:51:47 ad Exp $");
#include <errno.h>
#include <sys/time.h>
@ -324,8 +324,8 @@ pthread_cond_signal(pthread_cond_t *cond)
* deferred wakeup list. The waiter will be set running when the
* caller (this thread) releases the mutex.
*/
if (mutex != NULL && pthread__mutex_owned(self, mutex) &&
self->pt_nwaiters < pthread__unpark_max) {
if (mutex != NULL && self->pt_nwaiters < pthread__unpark_max &&
pthread__mutex_deferwake(self, mutex)) {
signaled->pt_sleepobj = NULL;
signaled->pt_sleeponq = 0;
pthread_spinunlock(&cond->ptc_lock);
@ -363,7 +363,7 @@ pthread_cond_broadcast(pthread_cond_t *cond)
* Try to defer waking threads (see pthread_cond_signal()).
* Only transfer waiters for which there is no pending wakeup.
*/
if (mutex != NULL && pthread__mutex_owned(self, mutex)) {
if (mutex != NULL && pthread__mutex_deferwake(self, mutex)) {
for (signaled = PTQ_FIRST(&cond->ptc_waiters);
signaled != NULL;
signaled = next) {

4
lib/libpthread/pthread_int.h
View File

@ -1,4 +1,4 @@
/* $NetBSD: pthread_int.h,v 1.54 2007/09/11 18:11:29 ad Exp $ */
/* $NetBSD: pthread_int.h,v 1.55 2007/09/13 23:51:47 ad Exp $ */
/*-
* Copyright (c) 2001, 2002, 2003, 2006, 2007 The NetBSD Foundation, Inc.
@ -256,7 +256,7 @@ void pthread__membar_full(void);
void pthread__membar_producer(void);
void pthread__membar_consumer(void);
int pthread__mutex_owned(pthread_t, pthread_mutex_t *);
int pthread__mutex_deferwake(pthread_t, pthread_mutex_t *);
int pthread__mutex_catchup(pthread_mutex_t *);
#ifndef pthread__smt_pause

6
lib/libpthread/pthread_mutex.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: pthread_mutex.c,v 1.35 2007/09/11 10:27:44 ad Exp $ */
/* $NetBSD: pthread_mutex.c,v 1.36 2007/09/13 23:51:47 ad Exp $ */
/*-
* Copyright (c) 2001, 2003, 2006, 2007 The NetBSD Foundation, Inc.
@ -37,7 +37,7 @@
*/
#include <sys/cdefs.h>
__RCSID("$NetBSD: pthread_mutex.c,v 1.35 2007/09/11 10:27:44 ad Exp $");
__RCSID("$NetBSD: pthread_mutex.c,v 1.36 2007/09/13 23:51:47 ad Exp $");
#include <errno.h>
#include <limits.h>
@ -469,7 +469,7 @@ pthread_once(pthread_once_t *once_control, void (*routine)(void))
}
int
pthread__mutex_owned(pthread_t thread, pthread_mutex_t *mutex)
pthread__mutex_deferwake(pthread_t thread, pthread_mutex_t *mutex)
{
return mutex->ptm_owner == thread;

37
lib/libpthread/pthread_mutex2.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: pthread_mutex2.c,v 1.6 2007/09/11 18:11:29 ad Exp $ */
/* $NetBSD: pthread_mutex2.c,v 1.7 2007/09/13 23:51:47 ad Exp $ */
/*-
* Copyright (c) 2001, 2003, 2006, 2007 The NetBSD Foundation, Inc.
@ -37,7 +37,7 @@
*/
#include <sys/cdefs.h>
__RCSID("$NetBSD: pthread_mutex2.c,v 1.6 2007/09/11 18:11:29 ad Exp $");
__RCSID("$NetBSD: pthread_mutex2.c,v 1.7 2007/09/13 23:51:47 ad Exp $");
#include <errno.h>
#include <limits.h>
@ -63,6 +63,8 @@ __RCSID("$NetBSD: pthread_mutex2.c,v 1.6 2007/09/11 18:11:29 ad Exp $");
#define MUTEX_RECURSIVE_BIT (0x02UL)
#define MUTEX_THREAD (-16L)
#define MUTEX_DEFERRED(x) (*(char *)&(x)->ptm_lock)
#define MUTEX_HAS_WAITERS(x) ((uintptr_t)(x) & MUTEX_WAITERS_BIT)
#define MUTEX_RECURSIVE(x) ((uintptr_t)(x) & MUTEX_RECURSIVE_BIT)
#define MUTEX_OWNER(x) ((uintptr_t)(x) & MUTEX_THREAD)
@ -128,6 +130,7 @@ pthread_mutex_init(pthread_mutex_t *ptm, const pthread_mutexattr_t *attr)
ptm->ptm_magic = _PT_MUTEX_MAGIC;
ptm->ptm_waiters = NULL;
ptm->ptm_private = NULL;
MUTEX_DEFERRED(ptm) = 0;
return 0;
}
@ -332,9 +335,12 @@ pthread_mutex_unlock(pthread_mutex_t *ptm)
{
void *owner;
pthread_t self;
char deferred;
self = pthread__self();
owner = self;
deferred = MUTEX_DEFERRED(ptm);
MUTEX_DEFERRED(ptm) = 0;
if (__predict_false(!mutex_cas(&ptm->ptm_owner, &owner, NULL)))
return pthread__mutex_unlock_slow(ptm);
@ -343,7 +349,7 @@ pthread_mutex_unlock(pthread_mutex_t *ptm)
* There were no waiters, but we may have deferred waking
* other threads until mutex unlock - we must wake them now.
*/
if (self->pt_nwaiters != 0)
if (deferred)
return pthread__mutex_catchup(ptm);
return 0;
@ -353,6 +359,7 @@ NOINLINE static int
pthread__mutex_unlock_slow(pthread_mutex_t *ptm)
{
pthread_t self, owner, new;
char deferred;
int weown;
pthread__error(EINVAL, "Invalid mutex",
@ -386,19 +393,22 @@ pthread__mutex_unlock_slow(pthread_mutex_t *ptm)
* Release the mutex. If there appear to be waiters, then
* wake them up.
*/
if (new != owner) {
owner = pthread__atomic_swap_ptr(&ptm->ptm_owner, new);
if (MUTEX_HAS_WAITERS(owner) != 0) {
pthread__mutex_wakeup(self, ptm);
return 0;
}
if (new == owner)
return 0;
deferred = MUTEX_DEFERRED(ptm);
MUTEX_DEFERRED(ptm) = 0;
owner = pthread__atomic_swap_ptr(&ptm->ptm_owner, new);
if (MUTEX_HAS_WAITERS(owner) != 0) {
pthread__mutex_wakeup(self, ptm);
return 0;
}
/*
* There were no waiters, but we may have deferred waking
* other threads until mutex unlock - we must wake them now.
*/
if (self->pt_nwaiters != 0)
if (deferred)
return pthread__mutex_catchup(ptm);
return 0;
@ -543,10 +553,13 @@ pthread_once(pthread_once_t *once_control, void (*routine)(void))
}
int
pthread__mutex_owned(pthread_t thread, pthread_mutex_t *ptm)
pthread__mutex_deferwake(pthread_t thread, pthread_mutex_t *ptm)
{
return MUTEX_OWNER(ptm->ptm_owner) == (uintptr_t)thread;
if (MUTEX_OWNER(ptm->ptm_owner) != (uintptr_t)thread)
return 0;
MUTEX_DEFERRED(ptm) = 1;
return 1;
}
#endif /* PTHREAD__HAVE_ATOMIC */