You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
38 lines
1.3 KiB
38 lines
1.3 KiB
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; |
|
}
|
|
|