Author: mjg
Date: Wed Feb 14 20:37:33 2018
New Revision: 329276
URL: https://svnweb.freebsd.org/changeset/base/329276
Log:
rwlock: diff-reduction of runlock compared to sx sunlock
Modified:
head/sys/kern/kern_rwlock.c
Modified: head/sys/kern/kern_rwlock.c
==============================================================================
--- head/sys/kern/kern_rwlock.c Wed Feb 14 20:26:09 2018 (r329275)
+++ head/sys/kern/kern_rwlock.c Wed Feb 14 20:37:33 2018 (r329276)
@@ -760,22 +760,19 @@ __rw_runlock_hard(struct rwlock *rw, struct thread *td
if (SCHEDULER_STOPPED())
return;
+ if (__rw_runlock_try(rw, td, &v))
+ goto out_lockstat;
+
+ /*
+ * Ok, we know we have waiters and we think we are the
+ * last reader, so grab the turnstile lock.
+ */
+ turnstile_chain_lock(&rw->lock_object);
+ v = RW_READ_VALUE(rw);
for (;;) {
if (__rw_runlock_try(rw, td, &v))
break;
- /*
- * Ok, we know we have waiters and we think we are the
- * last reader, so grab the turnstile lock.
- */
- turnstile_chain_lock(&rw->lock_object);
- v = RW_READ_VALUE(rw);
-retry_ts:
- if (__rw_runlock_try(rw, td, &v)) {
- turnstile_chain_unlock(&rw->lock_object);
- break;
- }
-
v &= (RW_LOCK_WAITERS | RW_LOCK_WRITE_SPINNER);
MPASS(v & RW_LOCK_WAITERS);
@@ -803,7 +800,7 @@ retry_ts:
}
v |= RW_READERS_LOCK(1);
if (!atomic_fcmpset_rel_ptr(&rw->rw_lock, &v, setv))
- goto retry_ts;
+ continue;
if (LOCK_LOG_TEST(&rw->lock_object, 0))
CTR2(KTR_LOCK, "%s: %p last succeeded with waiters",
__func__, rw);
@@ -819,10 +816,11 @@ retry_ts:
MPASS(ts != NULL);
turnstile_broadcast(ts, queue);
turnstile_unpend(ts, TS_SHARED_LOCK);
- turnstile_chain_unlock(&rw->lock_object);
td->td_rw_rlocks--;
break;
}
+ turnstile_chain_unlock(&rw->lock_object);
+out_lockstat:
LOCKSTAT_PROFILE_RELEASE_RWLOCK(rw__release, rw, LOCKSTAT_READER);
}
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