Add sync.Barrier; Add sync.Blocking_Mutex for unix

core/sync/barrier.odin

@@ -0,0 +1,81 @@
+package sync
+
+
+// A barrier enabling multiple threads to synchronize the beginning of some computation
+/*
+ * Example:
+ *
+ * 	package example
+ *
+ * 	import "core:fmt"
+ * 	import "core:sync"
+ * 	import "core:thread"
+ *
+ * 	barrier := &sync.Barrier{};
+ *
+ * 	main :: proc() {
+ * 		fmt.println("Start");
+ *
+ * 		THREAD_COUNT :: 4;
+ * 		threads: [THREAD_COUNT]^thread.Thread;
+ *
+ * 		sync.barrier_init(barrier, THREAD_COUNT);
+ * 		defer sync.barrier_destroy(barrier);
+ *
+ *
+ * 		for _, i in threads {
+ * 			threads[i] = thread.create_and_start(proc(t: ^thread.Thread) {
+ * 				// Same messages will be printed together but without any interleaving
+ * 				fmt.println("Getting ready!");
+ * 				sync.barrier_wait(barrier);
+ * 				fmt.println("Off their marks they go!");
+ * 			});
+ * 		}
+ *
+ * 		for t in threads {
+ * 			thread.destroy(t); // join and free thread
+ * 		}
+ * 		fmt.println("Finished");
+ * 	}
+ *
+ */
+Barrier :: struct {
+	mutex: Blocking_Mutex,
+	cond:  Condition,
+	index:         int,
+	generation_id: int,
+	thread_count:  int,
+}
+
+barrier_init :: proc(b: ^Barrier, thread_count: int) {
+	blocking_mutex_init(&b.mutex);
+	condition_init(&b.cond, &b.mutex);
+	b.index = 0;
+	b.generation_id = 0;
+	b.thread_count = thread_count;
+}
+
+barrier_destroy :: proc(b: ^Barrier) {
+	blocking_mutex_destroy(&b.mutex);
+	condition_destroy(&b.cond);
+}
+
+// Block the current thread until all threads have rendezvoused
+// Barrier can be reused after all threads rendezvoused once, and can be used continuously
+barrier_wait :: proc(b: ^Barrier) -> (is_leader: bool) {
+	blocking_mutex_lock(&b.mutex);
+	defer blocking_mutex_unlock(&b.mutex);
+	local_gen := b.generation_id;
+	b.index += 1;
+	if b.index < b.thread_count {
+		for local_gen == b.generation_id && b.index < b.thread_count {
+			condition_wait_for(&b.cond);
+		}
+		return false;
+	}
+
+	b.index = 0;
+	b.generation_id += 1;
+	condition_broadcast(&b.cond);
+	return true;
+}