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| author | Jangwoong Kim <6812skiii@gmail.com> | 2021-12-14 21:30:51 +0900 |
|---|---|---|
| committer | Sunil K Pandey <skpgkp2@gmail.com> | 2022-09-28 07:34:08 -0700 |
| commit | 43760d33d78f9ea8c8af942b570112ee801b99df (patch) | |
| tree | 9c81e1a82767d11856aef7aa6a4250136896cb49 | |
| parent | 6bcfbee7277e4faa4b693bd965931f0d1883005d (diff) | |
| download | glibc-43760d33d78f9ea8c8af942b570112ee801b99df.tar glibc-43760d33d78f9ea8c8af942b570112ee801b99df.tar.gz glibc-43760d33d78f9ea8c8af942b570112ee801b99df.tar.bz2 glibc-43760d33d78f9ea8c8af942b570112ee801b99df.zip | |
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)
| -rw-r--r-- | nptl/pthread_mutex_lock.c | 5 |
1 files changed, 2 insertions, 3 deletions
diff --git a/nptl/pthread_mutex_lock.c b/nptl/pthread_mutex_lock.c index 49901ffa0a..bbe754a272 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; } |