From dc95322e18615392eea69de355edd735a15a8f36 Mon Sep 17 00:00:00 2001 From: Rich Felker Date: Mon, 20 Oct 2014 00:22:51 -0400 Subject: [PATCH] manually "shrink wrap" fast path in pthread_once this change is a workaround for the inability of current compilers to perform "shrink wrapping" optimizations. in casual testing, it roughly doubled the performance of pthread_once when called on an already-finished once control object. --- src/thread/pthread_once.c | 20 ++++++++++++-------- 1 file changed, 12 insertions(+), 8 deletions(-) diff --git a/src/thread/pthread_once.c b/src/thread/pthread_once.c index 7c47385c..df655ef9 100644 --- a/src/thread/pthread_once.c +++ b/src/thread/pthread_once.c @@ -8,15 +8,8 @@ static void undo(void *control) __wake(control, -1, 1); } -int __pthread_once(pthread_once_t *control, void (*init)(void)) +int __pthread_once_full(pthread_once_t *control, void (*init)(void)) { - /* Return immediately if init finished before, but ensure that - * effects of the init routine are visible to the caller. */ - if (*control == 2) { - a_barrier(); - return 0; - } - /* Try to enter initializing state. Four possibilities: * 0 - we're the first or the other cancelled; run init * 1 - another thread is running init; wait @@ -43,4 +36,15 @@ int __pthread_once(pthread_once_t *control, void (*init)(void)) } } +int __pthread_once(pthread_once_t *control, void (*init)(void)) +{ + /* Return immediately if init finished before, but ensure that + * effects of the init routine are visible to the caller. */ + if (*control == 2) { + a_barrier(); + return 0; + } + return __pthread_once_full(control, init); +} + weak_alias(__pthread_once, pthread_once); -- 2.25.1