svn commit: r197735 - head/sys/kern
Attilio Rao
attilio at FreeBSD.org
Sat Oct 3 15:02:55 UTC 2009
Author: attilio
Date: Sat Oct 3 15:02:55 2009
New Revision: 197735
URL: http://svn.freebsd.org/changeset/base/197735
Log:
When releasing a lockmgr held in shared way we need to use a write memory
barrier in order to avoid, on architectures which doesn't have strong
ordered writes, CPU instructions reordering.
Diagnosed by: fabio
Modified:
head/sys/kern/kern_lock.c
Modified: head/sys/kern/kern_lock.c
==============================================================================
--- head/sys/kern/kern_lock.c Sat Oct 3 14:38:22 2009 (r197734)
+++ head/sys/kern/kern_lock.c Sat Oct 3 15:02:55 2009 (r197735)
@@ -241,7 +241,7 @@ wakeupshlk(struct lock *lk, const char *
* and return.
*/
if (LK_SHARERS(x) > 1) {
- if (atomic_cmpset_ptr(&lk->lk_lock, x,
+ if (atomic_cmpset_rel_ptr(&lk->lk_lock, x,
x - LK_ONE_SHARER))
break;
continue;
@@ -254,7 +254,7 @@ wakeupshlk(struct lock *lk, const char *
if ((x & LK_ALL_WAITERS) == 0) {
MPASS((x & ~LK_EXCLUSIVE_SPINNERS) ==
LK_SHARERS_LOCK(1));
- if (atomic_cmpset_ptr(&lk->lk_lock, x, LK_UNLOCKED))
+ if (atomic_cmpset_rel_ptr(&lk->lk_lock, x, LK_UNLOCKED))
break;
continue;
}
@@ -280,7 +280,7 @@ wakeupshlk(struct lock *lk, const char *
queue = SQ_SHARED_QUEUE;
}
- if (!atomic_cmpset_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x,
+ if (!atomic_cmpset_rel_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x,
v)) {
sleepq_release(&lk->lock_object);
continue;
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