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From: Mateusz Guzik <mjg@FreeBSD.org>
Date: Sat, 13 Jan 2018 00:05:31 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r327905 - head/sys/kern
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Author: mjg
Date: Sat Jan 13 00:05:31 2018
New Revision: 327905
URL: https://svnweb.freebsd.org/changeset/base/327905

Log:
  rwlock: try regular read unlock even in the hard path
  
  Saves on turnstile trips if the lock got more readers.

Modified:
  head/sys/kern/kern_rwlock.c

Modified: head/sys/kern/kern_rwlock.c
==============================================================================
--- head/sys/kern/kern_rwlock.c	Sat Jan 13 00:04:11 2018	(r327904)
+++ head/sys/kern/kern_rwlock.c	Sat Jan 13 00:05:31 2018	(r327905)
@@ -771,9 +771,9 @@ __rw_runlock_hard(struct rwlock *rw, struct thread *td
 		turnstile_chain_lock(&rw->lock_object);
 		v = RW_READ_VALUE(rw);
 retry_ts:
-		if (__predict_false(RW_READERS(v) > 1)) {
+		if (__rw_runlock_try(rw, td, &v)) {
 			turnstile_chain_unlock(&rw->lock_object);
-			continue;
+			break;
 		}
 
 		v &= (RW_LOCK_WAITERS | RW_LOCK_WRITE_SPINNER);