From a113434cd68ce30642c4995b1caadcd084be6f09 Mon Sep 17 00:00:00 2001 From: Rich Felker Date: Wed, 6 Apr 2011 12:24:34 -0400 Subject: major semaphore improvements (performance and correctness) 1. make sem_[timed]wait interruptible by signals, per POSIX 2. keep a waiter count in order to avoid unnecessary futex wake syscalls --- src/thread/sem_trywait.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) (limited to 'src/thread/sem_trywait.c') diff --git a/src/thread/sem_trywait.c b/src/thread/sem_trywait.c index c5370c70..beb7aa5d 100644 --- a/src/thread/sem_trywait.c +++ b/src/thread/sem_trywait.c @@ -3,9 +3,8 @@ int sem_trywait(sem_t *sem) { - int val = a_fetch_add(sem->__val, -1); - if (val > 0) return 0; - if (!a_fetch_add(sem->__val, 1)) + if (a_fetch_add(sem->__val, -1) > 0) return 0; + if (!a_fetch_add(sem->__val, 1) && sem->__val[1]) __wake(sem->__val, 1, 0); errno = EAGAIN; return -1; -- cgit v1.2.1