forked from rpms/glibc
39 lines
1.3 KiB
Diff
39 lines
1.3 KiB
Diff
|
commit 43760d33d78f9ea8c8af942b570112ee801b99df
|
||
|
|
Author: Jangwoong Kim <6812skiii@gmail.com>
|
||
|
|
Date: Tue Dec 14 21:30:51 2021 +0900
|
||
|
|
|
||
|
|
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>
|
||
|
|
(cherry picked from commit 6b8dbbd03ac88f169b65b5c7d7278576a11d2e44)
|
||
|
|
|
||
|
|
diff --git a/nptl/pthread_mutex_lock.c b/nptl/pthread_mutex_lock.c
|
||
|
|
index 49901ffa0a96d659..bbe754a272b97d91 100644
|
||
|
|
--- a/nptl/pthread_mutex_lock.c
|
||
|
|
+++ b/nptl/pthread_mutex_lock.c
|
||
|
|
@@ -147,10 +147,9 @@ 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;
|
||
|
|
}
|