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Close a window in which we can not notice a recently-slept-on-our

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mutex thread, thus leaving a thread sleeping on an unlocked mutex.

Reviewed by myself and Christos.

Problem reported by Arne H. Juul, arnej at pvv dot ntnu dot no,
in PR 26208. This fix represents option 1 presented in the PR.
This commit is contained in:
wrstuden 2006-08-22 21:46:09 +00:00
parent a9815feffa
commit 25b0eaef3c
1 changed files with 6 additions and 6 deletions
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12
lib/libpthread/pthread_mutex.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: pthread_mutex.c,v 1.21 2005/10/19 02:15:03 chs Exp $ */
/* $NetBSD: pthread_mutex.c,v 1.22 2006/08/22 21:46:09 wrstuden Exp $ */
/*-
* Copyright (c) 2001, 2003 The NetBSD Foundation, Inc.
@ -37,7 +37,7 @@
*/
#include <sys/cdefs.h>
__RCSID("$NetBSD: pthread_mutex.c,v 1.21 2005/10/19 02:15:03 chs Exp $");
__RCSID("$NetBSD: pthread_mutex.c,v 1.22 2006/08/22 21:46:09 wrstuden Exp $");
#include <errno.h>
#include <limits.h>
@ -337,12 +337,13 @@ pthread_mutex_unlock(pthread_mutex_t *mutex)
GET_MUTEX_PRIVATE(mutex, mp);
self = pthread_self();
/*
* These tests can be performed without holding the
* interlock because these fields are only modified
* if we know we own the mutex.
*/
weown = (pthread__id(mutex->ptm_owner) == pthread__self());
weown = (pthread__id(mutex->ptm_owner) == self);
switch (mp->type) {
case PTHREAD_MUTEX_RECURSIVE:
if (!weown)
@ -378,9 +379,8 @@ pthread_mutex_unlock(pthread_mutex_t *mutex)
* examination of the queue; if so, no harm is done, as the
* waiter will loop and see that the mutex is still locked.
*/
pthread_spinlock(self, &mutex->ptm_interlock);
if (!PTQ_EMPTY(&mutex->ptm_blocked)) {
self = pthread__self();
pthread_spinlock(self, &mutex->ptm_interlock);
blocked = PTQ_FIRST(&mutex->ptm_blocked);
if (blocked) {
PTQ_REMOVE(&mutex->ptm_blocked, blocked, pt_sleep);
@ -388,8 +388,8 @@ pthread_mutex_unlock(pthread_mutex_t *mutex)
/* Give the head of the blocked queue another try. */
pthread__sched(self, blocked);
}
pthread_spinunlock(self, &mutex->ptm_interlock);
}
pthread_spinunlock(self, &mutex->ptm_interlock);
return 0;
}