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authorLennart Poettering <lennart@poettering.net>2009-04-21 21:25:27 +0200
committerLennart Poettering <lennart@poettering.net>2009-04-21 21:25:27 +0200
commitfbbcfae769770ca1191e0610ad43722a5768aa40 (patch)
treef8fdb9502a89ecbe703c333d5e033cc0d1e4661b
parent391d50cd26a57b36deee48da1548aa7da88d1a1d (diff)
semaphore: introduce static semaphores
-rw-r--r--src/pulsecore/semaphore-posix.c22
-rw-r--r--src/pulsecore/semaphore.h15
2 files changed, 37 insertions, 0 deletions
diff --git a/src/pulsecore/semaphore-posix.c b/src/pulsecore/semaphore-posix.c
index 616d897d..2aa1bce9 100644
--- a/src/pulsecore/semaphore-posix.c
+++ b/src/pulsecore/semaphore-posix.c
@@ -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;
+}
diff --git a/src/pulsecore/semaphore.h b/src/pulsecore/semaphore.h
index dc3ca6a5..2bf81496 100644
--- a/src/pulsecore/semaphore.h
+++ b/src/pulsecore/semaphore.h
@@ -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