diff options
| author | Mateusz Guzik <mjg@FreeBSD.org> | 2017-11-17 02:25:04 +0000 |
|---|---|---|
| committer | Mateusz Guzik <mjg@FreeBSD.org> | 2017-11-17 02:25:04 +0000 |
| commit | 8448e020813ca77e5b4ff60411eac6ddcb955e6b (patch) | |
| tree | fb2e0279b0e261bb4f1e4e1be8f22b51c65dbb0a /sys | |
| parent | ae7d25a4d736392ecf325f3f1386d405e572e830 (diff) | |
| download | src-8448e020813ca77e5b4ff60411eac6ddcb955e6b.tar.gz src-8448e020813ca77e5b4ff60411eac6ddcb955e6b.zip | |
mtx: unlock before traversing threads to wake up
This shortens the lock hold time while not affecting corretness.
All the woken up threads end up competing can lose the race against
a completely unrelated thread getting the lock anyway.
Notes
Notes:
svn path=/head/; revision=325920
Diffstat (limited to 'sys')
| -rw-r--r-- | sys/kern/kern_mutex.c | 9 |
1 files changed, 5 insertions, 4 deletions
diff --git a/sys/kern/kern_mutex.c b/sys/kern/kern_mutex.c index 435cbe753bf7..27df45c10757 100644 --- a/sys/kern/kern_mutex.c +++ b/sys/kern/kern_mutex.c @@ -629,7 +629,8 @@ __mtx_lock_sleep(volatile uintptr_t *c, uintptr_t v) #ifdef KDTRACE_HOOKS sleep_time -= lockstat_nsecs(&m->lock_object); #endif - turnstile_wait(ts, mtx_owner(m), TS_EXCLUSIVE_QUEUE); + MPASS(owner == mtx_owner(m)); + turnstile_wait(ts, owner, TS_EXCLUSIVE_QUEUE); #ifdef KDTRACE_HOOKS sleep_time += lockstat_nsecs(&m->lock_object); sleep_cnt++; @@ -1002,7 +1003,7 @@ __mtx_unlock_sleep(volatile uintptr_t *c) { struct mtx *m; struct turnstile *ts; - uintptr_t tid, v; + uintptr_t tid; if (SCHEDULER_STOPPED()) return; @@ -1028,12 +1029,12 @@ __mtx_unlock_sleep(volatile uintptr_t *c) * can be removed from the hash list if it is empty. */ turnstile_chain_lock(&m->lock_object); + _mtx_release_lock_quick(m); ts = turnstile_lookup(&m->lock_object); + MPASS(ts != NULL); if (LOCK_LOG_TEST(&m->lock_object, opts)) CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p contested", m); - MPASS(ts != NULL); turnstile_broadcast(ts, TS_EXCLUSIVE_QUEUE); - _mtx_release_lock_quick(m); /* * This turnstile is now no longer associated with the mutex. We can |