util: move pipe_barrier into src/util and rename to util_barrier

The #if guard is probably not 100% equivalent to the previous PIPE_OS
check, but if anything it should be an over-approximation (are there
pthread implementations without barriers?), so people will get either
a good implementation or compile errors that are easy to fix.

Reviewed-by: Marek Olšák <[email protected]>

1 files changed, 74 insertions, 0 deletions

diff --git a/src/util/u_thread.h b/src/util/u_thread.h
index 6b5458af86a..e484d8aa74f 100644
--- a/src/util/u_thread.h
+++ b/src/util/u_thread.h
@@ -100,4 +100,78 @@ static inline bool u_thread_is_self(thrd_t thread)
    return false;
 }
 
+/*
+ * util_barrier
+ */
+
+#if defined(HAVE_PTHREAD)
+
+typedef pthread_barrier_t util_barrier;
+
+static inline void util_barrier_init(util_barrier *barrier, unsigned count)
+{
+   pthread_barrier_init(barrier, NULL, count);
+}
+
+static inline void util_barrier_destroy(util_barrier *barrier)
+{
+   pthread_barrier_destroy(barrier);
+}
+
+static inline void util_barrier_wait(util_barrier *barrier)
+{
+   pthread_barrier_wait(barrier);
+}
+
+
+#else /* If the OS doesn't have its own, implement barriers using a mutex and a condvar */
+
+typedef struct {
+   unsigned count;
+   unsigned waiters;
+   uint64_t sequence;
+   mtx_t mutex;
+   cnd_t condvar;
+} util_barrier;
+
+static inline void util_barrier_init(util_barrier *barrier, unsigned count)
+{
+   barrier->count = count;
+   barrier->waiters = 0;
+   barrier->sequence = 0;
+   (void) mtx_init(&barrier->mutex, mtx_plain);
+   cnd_init(&barrier->condvar);
+}
+
+static inline void util_barrier_destroy(util_barrier *barrier)
+{
+   assert(barrier->waiters == 0);
+   mtx_destroy(&barrier->mutex);
+   cnd_destroy(&barrier->condvar);
+}
+
+static inline void util_barrier_wait(util_barrier *barrier)
+{
+   mtx_lock(&barrier->mutex);
+
+   assert(barrier->waiters < barrier->count);
+   barrier->waiters++;
+
+   if (barrier->waiters < barrier->count) {
+      uint64_t sequence = barrier->sequence;
+
+      do {
+         cnd_wait(&barrier->condvar, &barrier->mutex);
+      } while (sequence == barrier->sequence);
+   } else {
+      barrier->waiters = 0;
+      barrier->sequence++;
+      cnd_broadcast(&barrier->condvar);
+   }
+
+   mtx_unlock(&barrier->mutex);
+}
+
+#endif
+
 #endif /* U_THREAD_H_ */