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rwlock: diff-reduction of runlock compared to sx sunlock

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This commit is contained in:
Mateusz Guzik 2018-02-14 20:37:33 +00:00
parent 834063202a
commit f795032b47
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=329276
1 changed files with 12 additions and 14 deletions
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26
sys/kern/kern_rwlock.c
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@ -760,22 +760,19 @@ __rw_runlock_hard(struct rwlock *rw, struct thread *td, uintptr_t v
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);
}