rwlock: unlock before traversing threads to wake up
While here perform a minor cleanup of the unlock path.
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@ -1081,7 +1081,7 @@ __rw_wunlock_hard(volatile uintptr_t *c, uintptr_t tid, const char *file,
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{
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struct rwlock *rw;
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struct turnstile *ts;
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uintptr_t v;
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uintptr_t v, setv;
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int queue;
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if (SCHEDULER_STOPPED())
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@ -1108,8 +1108,6 @@ __rw_wunlock_hard(volatile uintptr_t *c, uintptr_t tid, const char *file,
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CTR2(KTR_LOCK, "%s: %p contested", __func__, rw);
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turnstile_chain_lock(&rw->lock_object);
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ts = turnstile_lookup(&rw->lock_object);
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MPASS(ts != NULL);
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/*
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* Use the same algo as sx locks for now. Prefer waking up shared
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@ -1127,19 +1125,23 @@ __rw_wunlock_hard(volatile uintptr_t *c, uintptr_t tid, const char *file,
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* there that could be worked around either by waking both queues
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* of waiters or doing some complicated lock handoff gymnastics.
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*/
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v = RW_UNLOCKED;
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if (rw->rw_lock & RW_LOCK_WRITE_WAITERS) {
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setv = RW_UNLOCKED;
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v = RW_READ_VALUE(rw);
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queue = TS_SHARED_QUEUE;
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if (v & RW_LOCK_WRITE_WAITERS) {
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queue = TS_EXCLUSIVE_QUEUE;
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v |= (rw->rw_lock & RW_LOCK_READ_WAITERS);
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} else
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queue = TS_SHARED_QUEUE;
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setv |= (v & RW_LOCK_READ_WAITERS);
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}
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atomic_store_rel_ptr(&rw->rw_lock, setv);
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/* Wake up all waiters for the specific queue. */
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if (LOCK_LOG_TEST(&rw->lock_object, 0))
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CTR3(KTR_LOCK, "%s: %p waking up %s waiters", __func__, rw,
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queue == TS_SHARED_QUEUE ? "read" : "write");
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ts = turnstile_lookup(&rw->lock_object);
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MPASS(ts != NULL);
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turnstile_broadcast(ts, queue);
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atomic_store_rel_ptr(&rw->rw_lock, v);
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turnstile_unpend(ts, TS_EXCLUSIVE_LOCK);
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turnstile_chain_unlock(&rw->lock_object);
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}
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