RepoMirrors
/
musl
mirror of git://git.musl-libc.org/musl
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

eliminate global waiters count in pthread_once

This commit is contained in:
Rich Felker 2014-10-13 18:26:28 -04:00
parent df37d3960a
commit 0054840839
1 changed files with 13 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

22
src/thread/pthread_once.c
View File

@ -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;