Author: marcel
Date: Mon Dec 14 01:26:01 2009
New Revision: 200498
URL: http://svn.freebsd.org/changeset/base/200498
Log:
Work-around a race condition on ia64 while unlocking a contested lock.
The race condition is believed to be in UMTX_OP_MUTEX_WAKE. On ia64,
we simply go to the kernel to unlock.
The big question is why this is only a race condition on ia64...
MFC after: 3 days
Modified:
head/lib/libthr/thread/thr_umtx.c
Modified: head/lib/libthr/thread/thr_umtx.c
==============================================================================
--- head/lib/libthr/thread/thr_umtx.c Mon Dec 14 01:10:05 2009
(r200497)
+++ head/lib/libthr/thread/thr_umtx.c Mon Dec 14 01:26:01 2009
(r200498)
@@ -112,10 +112,13 @@ __thr_umutex_timedlock(struct umutex *mt
int
__thr_umutex_unlock(struct umutex *mtx, uint32_t id)
{
+#ifndef __ia64__
+ /* XXX this logic has a race-condition on ia64. */
if ((mtx->m_flags & (UMUTEX_PRIO_PROTECT | UMUTEX_PRIO_INHERIT)) == 0) {
atomic_cmpset_rel_32(&mtx->m_owner, id | UMUTEX_CONTESTED,
UMUTEX_CONTESTED);
return _umtx_op_err(mtx, UMTX_OP_MUTEX_WAKE, 0, 0, 0);
}
+#endif /* __ia64__ */
return _umtx_op_err(mtx, UMTX_OP_MUTEX_UNLOCK, 0, 0, 0);
}
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