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authorRich Felker <dalias@aerifal.cx>2014-10-13 18:26:28 -0400
committerRich Felker <dalias@aerifal.cx>2014-10-13 18:26:28 -0400
commit00548408398ced546c540dab773ea66cea4fe1c2 (patch)
tree547a52d425979a2528953a2252c11d424b32b0ab /src
parentdf37d3960abec482e17fad2274a99b790f6cc08b (diff)
downloadmusl-00548408398ced546c540dab773ea66cea4fe1c2.tar.gz
eliminate global waiters count in pthread_once
Diffstat (limited to 'src')
-rw-r--r--src/thread/pthread_once.c22
1 files changed, 13 insertions, 9 deletions
diff --git a/src/thread/pthread_once.c b/src/thread/pthread_once.c
index b7388b93..7c47385c 100644
--- a/src/thread/pthread_once.c
+++ b/src/thread/pthread_once.c
@@ -2,14 +2,14 @@
static void undo(void *control)
{
- a_store(control, 0);
- __wake(control, 1, 1);
+ /* Wake all waiters, since the waiter status is lost when
+ * resetting control to the initial state. */
+ if (a_swap(control, 0) == 3)
+ __wake(control, -1, 1);
}
int __pthread_once(pthread_once_t *control, void (*init)(void))
{
- static int waiters;
-
/* Return immediately if init finished before, but ensure that
* effects of the init routine are visible to the caller. */
if (*control == 2) {
@@ -17,10 +17,11 @@ int __pthread_once(pthread_once_t *control, void (*init)(void))
return 0;
}
- /* Try to enter initializing state. Three possibilities:
+ /* 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
- * 2 - another thread finished running init; just return */
+ * 2 - another thread finished running init; just return
+ * 3 - another thread is running init, waiters present; wait */
for (;;) switch (a_cas(control, 0, 1)) {
case 0:
@@ -28,11 +29,14 @@ int __pthread_once(pthread_once_t *control, void (*init)(void))
init();
pthread_cleanup_pop(0);
- a_store(control, 2);
- if (waiters) __wake(control, -1, 1);
+ if (a_swap(control, 2) == 3)
+ __wake(control, -1, 1);
return 0;
case 1:
- __wait(control, &waiters, 1, 1);
+ /* If this fails, so will __wait. */
+ a_cas(control, 1, 3);
+ case 3:
+ __wait(control, 0, 3, 1);
continue;
case 2:
return 0;