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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 13:52:51 -0700 |
| commit | 8b9ad5ec93ce8941a1e53cc3beea84293d998d2c (patch) | |
| tree | 3f1409b8eefd40d4519a53d3767d41b9443c91c7 | |
| parent | 60b8295333a076ff853c1093c502c7bf5197ab2e (diff) | |
| download | glibc-8b9ad5ec93ce8941a1e53cc3beea84293d998d2c.tar.gz glibc-8b9ad5ec93ce8941a1e53cc3beea84293d998d2c.tar.xz glibc-8b9ad5ec93ce8941a1e53cc3beea84293d998d2c.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 2895926953..253743f76c 100644 --- a/nptl/pthread_mutex_lock.c +++ b/nptl/pthread_mutex_lock.c @@ -138,10 +138,9 @@ __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; } |