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semaphore: introduce static semaphores

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This commit is contained in:
Lennart Poettering 2009-04-21 21:25:27 +02:00
parent 391d50cd26
commit fbbcfae769
2 changed files with 37 additions and 0 deletions
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22
src/pulsecore/semaphore-posix.c
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@ -65,3 +65,25 @@ void pa_semaphore_wait(pa_semaphore *s) {
pa_assert(ret == 0);
}
pa_semaphore* pa_static_semaphore_get(pa_static_semaphore *s, unsigned value) {
pa_semaphore *m;
pa_assert(s);
/* First, check if already initialized and short cut */
if ((m = pa_atomic_ptr_load(&s->ptr)))
return m;
/* OK, not initialized, so let's allocate, and fill in */
m = pa_semaphore_new(value);
if ((pa_atomic_ptr_cmpxchg(&s->ptr, NULL, m)))
return m;
pa_semaphore_free(m);
/* Him, filling in failed, so someone else must have filled in
* already */
pa_assert_se(m = pa_atomic_ptr_load(&s->ptr));
return m;
}

15
src/pulsecore/semaphore.h
View file

@ -22,6 +22,9 @@
USA.
***/
#include <pulsecore/macro.h>
#include <pulsecore/atomic.h>
typedef struct pa_semaphore pa_semaphore;
pa_semaphore* pa_semaphore_new(unsigned value);
@ -30,4 +33,16 @@ void pa_semaphore_free(pa_semaphore *m);
void pa_semaphore_post(pa_semaphore *m);
void pa_semaphore_wait(pa_semaphore *m);
/* Static semaphores are basically just atomically updated pointers to
* pa_semaphore objects */
typedef struct pa_static_semaphore {
pa_atomic_ptr_t ptr;
} pa_static_semaphore;
#define PA_STATIC_SEMAPHORE_INIT { PA_ATOMIC_PTR_INIT(NULL) }
/* When you call this make sure to pass always the same value parameter! */
pa_semaphore* pa_static_semaphore_get(pa_static_semaphore *m, unsigned value);
#endif