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authorJangwoong Kim <6812skiii@gmail.com>2021-12-14 21:30:51 +0900
committerH.J. Lu <hjl.tools@gmail.com>2022-01-20 05:05:09 -0800
commit6b8dbbd03ac88f169b65b5c7d7278576a11d2e44 (patch)
tree8c6053c6aabaea50c6706ecfb94eac3b8ca6ff83 /nptl/pthread_mutex_lock.c
parentf44820821a4ecdbb398375201b7c4ab9a1dd5983 (diff)
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nptl: Effectively skip CAS in spinlock loop
The commit:
"Add LLL_MUTEX_READ_LOCK [BZ #28537]"
SHA1: d672a98a1af106bd68deb15576710cd61363f7a6

introduced LLL_MUTEX_READ_LOCK, to skip CAS in spinlock loop
if atomic load fails. But, "continue" inside of do-while loop
does not skip the evaluation of escape expression, thus CAS
is not skipped.

Replace do-while with while and skip LLL_MUTEX_TRYLOCK if
LLL_MUTEX_READ_LOCK fails.

Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
Diffstat (limited to 'nptl/pthread_mutex_lock.c')
-rw-r--r--nptl/pthread_mutex_lock.c5
1 files changed, 2 insertions, 3 deletions
diff --git a/nptl/pthread_mutex_lock.c b/nptl/pthread_mutex_lock.c
index 31dfc7f1d7..d2e652d151 100644
--- a/nptl/pthread_mutex_lock.c
+++ b/nptl/pthread_mutex_lock.c
@@ -146,10 +146,9 @@ PTHREAD_MUTEX_LOCK (pthread_mutex_t *mutex)
 		  break;
 		}
 	      atomic_spin_nop ();
-	      if (LLL_MUTEX_READ_LOCK (mutex) != 0)
-		continue;
 	    }
-	  while (LLL_MUTEX_TRYLOCK (mutex) != 0);
+	  while (LLL_MUTEX_READ_LOCK (mutex) != 0
+		 || LLL_MUTEX_TRYLOCK (mutex) != 0);
 
 	  mutex->__data.__spins += (cnt - mutex->__data.__spins) / 8;
 	}