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mutex_vector_enter: put a read memory barrier between the final check that

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(1) the holder is no longer running and (2) the waiters bit is set. Needed
to ensure that the operations happen in the correct order.
This commit is contained in:
ad 2007-03-12 22:34:08 +00:00
parent 194273271b
commit bf8c3c1d7b
1 changed files with 4 additions and 4 deletions
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8
sys/kern/kern_mutex.c
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@ -1,4 +1,4 @@
/* $NetBSD: kern_mutex.c,v 1.12 2007/03/12 02:19:14 matt Exp $ */
/* $NetBSD: kern_mutex.c,v 1.13 2007/03/12 22:34:08 ad Exp $ */
/*-
* Copyright (c) 2002, 2006, 2007 The NetBSD Foundation, Inc.
@ -49,7 +49,7 @@
#define __MUTEX_PRIVATE
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: kern_mutex.c,v 1.12 2007/03/12 02:19:14 matt Exp $");
__KERNEL_RCSID(0, "$NetBSD: kern_mutex.c,v 1.13 2007/03/12 22:34:08 ad Exp $");
#include <sys/param.h>
#include <sys/proc.h>
@ -646,8 +646,8 @@ mutex_vector_enter(kmutex_t *mtx)
* If the waiters bit is not set it's unsafe to go asleep,
* as we might never be awoken.
*/
mb_read();
if (mutex_onproc(owner, &ci) || !MUTEX_HAS_WAITERS(mtx)) {
if ((mb_read(), mutex_onproc(owner, &ci)) ||
(mb_read(), !MUTEX_HAS_WAITERS(mtx))) {
turnstile_exit(mtx);
continue;
}