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Some software think a mutex can be destroyed after it owned it, for

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example, it uses a serialization point like following:
	pthread_mutex_lock(&mutex);
	pthread_mutex_unlock(&mutex);
	pthread_mutex_destroy(&muetx);
They think a previous lock holder should have already left the mutex and
is no longer referencing it, so they destroy it. To be maximum compatible
with such code, we use IA64 version to unlock the mutex in kernel, remove
the two steps unlocking code.
This commit is contained in:
David Xu 2012-03-18 00:22:29 +00:00
parent 1d73bec4c1
commit 1b008f5e51
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=233103
1 changed files with 0 additions and 7 deletions
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7
lib/libthr/thread/thr_umtx.c
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@ -154,13 +154,6 @@ __thr_umutex_timedlock(struct umutex *mtx, uint32_t id,
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);
}