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- In rw_wunlock_hard prefer to wakeup writers if there are both readers

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and writers available.  Doing otherwise can cause deadlocks as no
   read locks can proceed while there are write waiters.

Sponsored by:	Nokia
This commit is contained in:
Jeff Roberson 2008-02-07 06:16:54 +00:00
parent fb73a5ab6c
commit 0fef2c50b1
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=176076
1 changed files with 4 additions and 4 deletions
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8
sys/kern/kern_rwlock.c
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@ -679,11 +679,11 @@ _rw_wunlock_hard(struct rwlock *rw, uintptr_t tid, const char *file, int line)
* of waiters or doing some complicated lock handoff gymnastics.
*/
v = RW_UNLOCKED;
if (rw->rw_lock & RW_LOCK_READ_WAITERS) {
queue = TS_SHARED_QUEUE;
v |= (rw->rw_lock & RW_LOCK_WRITE_WAITERS);
} else
if (rw->rw_lock & RW_LOCK_WRITE_WAITERS) {
queue = TS_EXCLUSIVE_QUEUE;
v |= (rw->rw_lock & RW_LOCK_READ_WAITERS);
} else
queue = TS_SHARED_QUEUE;
/* Wake up all waiters for the specific queue. */
if (LOCK_LOG_TEST(&rw->lock_object, 0))