From 0b44a0315b47dd8eced9f3b7f31580cf14bbfc01 Mon Sep 17 00:00:00 2001 From: Rich Felker Date: Sat, 12 Feb 2011 00:22:29 -0500 Subject: initial check-in, version 0.5.0 --- src/thread/pthread_once.c | 38 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 38 insertions(+) create mode 100644 src/thread/pthread_once.c (limited to 'src/thread/pthread_once.c') diff --git a/src/thread/pthread_once.c b/src/thread/pthread_once.c new file mode 100644 index 00000000..72230054 --- /dev/null +++ b/src/thread/pthread_once.c @@ -0,0 +1,38 @@ +#include "pthread_impl.h" + +static void undo(void *control) +{ + a_store(control, 0); + __wake(control, 1, 0); +} + +int pthread_once(pthread_once_t *control, void (*init)(void)) +{ + static int waiters; + + /* Return immediately if init finished before */ + if (*control == 2) return 0; + + /* Try to enter initializing state. Three possibilities: + * 0 - we're the first or the other cancelled; run init + * 1 - another thread is running init; wait + * 2 - another thread finished running init; just return */ + + for (;;) switch (a_swap(control, 1)) { + case 0: + break; + case 1: + __wait(control, &waiters, 1, 0); + continue; + case 2: + a_store(control, 2); + return 0; + } + + pthread_cleanup_push(undo, control); + init(); + pthread_cleanup_pop(0); + + if (waiters) __wake(control, -1, 0); + return 0; +} -- cgit v1.2.1