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- Drop memory barriers in rw_try_upgrade(). We don't need an 'acq' memory

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barrier here as the earlier rw_rlock() already contained one.
- Comment fix.
This commit is contained in:
John Baldwin 2007-03-30 18:08:55 +00:00
parent 4efdbc8aea
commit b80ad3eea1
1 changed files with 4 additions and 4 deletions
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8
sys/kern/kern_rwlock.c
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@ -481,7 +481,7 @@ _rw_wlock_hard(struct rwlock *rw, uintptr_t tid, const char *file, int line)
* value RW_UNLOCKED | RW_LOCK_WRITE_WAITERS. If we see
* that value, try to acquire it once. Note that we have
* to preserve the RW_LOCK_WRITE_WAITERS flag as there are
* other writers waiting still. If we fail, restart the
* other writers waiting still. If we fail, restart the
* loop.
*/
if (v == (RW_UNLOCKED | RW_LOCK_WRITE_WAITERS)) {
@ -668,8 +668,8 @@ _rw_try_upgrade(struct rwlock *rw, const char *file, int line)
*/
tid = (uintptr_t)curthread;
if (!(rw->rw_lock & RW_LOCK_WRITE_WAITERS)) {
success = atomic_cmpset_acq_ptr(&rw->rw_lock,
RW_READERS_LOCK(1), tid);
success = atomic_cmpset_ptr(&rw->rw_lock, RW_READERS_LOCK(1),
tid);
goto out;
}
@ -689,7 +689,7 @@ _rw_try_upgrade(struct rwlock *rw, const char *file, int line)
* spinning.
*/
v = rw->rw_lock & RW_LOCK_WRITE_WAITERS;
success = atomic_cmpset_acq_ptr(&rw->rw_lock, RW_READERS_LOCK(1) | v,
success = atomic_cmpset_ptr(&rw->rw_lock, RW_READERS_LOCK(1) | v,
tid | v);
#ifdef ADAPTIVE_RWLOCKS
if (success && v && turnstile_lookup(&rw->lock_object) != NULL)