1 files changed, 184 insertions, 0 deletions
diff --git a/src/thread_pool.cpp b/src/thread_pool.cpp
new file mode 100644
index 000000000..2467ba609
--- /dev/null
+++ b/src/thread_pool.cpp
@@ -0,0 +1,184 @@
+// worker_queue.cpp
+
+#define WORKER_TASK_PROC(name) isize name(void *data)
+typedef WORKER_TASK_PROC(WorkerTaskProc);
+
+struct WorkerTask {
+	WorkerTaskProc *do_work;
+	void *data;
+	isize result;
+};
+
+
+struct ThreadPool {
+	gbMutex     mutex;
+	gbSemaphore sem_available;
+	gbAtomic32  processing_work_count;
+	bool        is_running;
+
+	gbAllocator allocator;
+
+	WorkerTask *tasks;
+	isize volatile task_head;
+	isize volatile task_tail;
+	isize volatile task_capacity;
+
+	gbThread *threads;
+	isize thread_count;
+
+	char worker_prefix[10];
+	i32 worker_prefix_len;
+};
+
+void thread_pool_init(ThreadPool *pool, gbAllocator const &a, isize thread_count, char const *worker_prefix = nullptr);
+void thread_pool_destroy(ThreadPool *pool);
+void thread_pool_start(ThreadPool *pool);
+void thread_pool_join(ThreadPool *pool);
+void thread_pool_add_task(ThreadPool *pool, WorkerTaskProc *proc, void *data);
+void thread_pool_kick(ThreadPool *pool);
+void thread_pool_kick_and_wait(ThreadPool *pool);
+GB_THREAD_PROC(worker_thread_internal);
+
+void thread_pool_init(ThreadPool *pool, gbAllocator const &a, isize thread_count, char const *worker_prefix) {
+	pool->allocator = a;
+	pool->task_head = 0;
+	pool->task_tail = 0;
+	pool->task_capacity = 1024;
+	pool->tasks = gb_alloc_array(a, WorkerTask, pool->task_capacity);
+	pool->thread_count = gb_max(thread_count, 0);
+	pool->threads = gb_alloc_array(a, gbThread, pool->thread_count);
+	gb_mutex_init(&pool->mutex);
+	gb_semaphore_init(&pool->sem_available);
+	pool->is_running = true;
+
+	pool->worker_prefix_len = 0;
+	if (worker_prefix) {
+		i32 worker_prefix_len = cast(i32)gb_strlen(worker_prefix);
+		worker_prefix_len = gb_min(worker_prefix_len, 10);
+		gb_memmove(pool->worker_prefix, worker_prefix, worker_prefix_len);
+		pool->worker_prefix_len = worker_prefix_len;
+	}
+
+	for (isize i = 0; i < pool->thread_count; i++) {
+		gbThread *t = &pool->threads[i];
+		gb_thread_init(t);
+		t->user_index = i;
+		#if 0
+		// TODO(bill): Fix this on Linux as it causes a seg-fault
+		if (pool->worker_prefix_len > 0) {
+			char worker_name[16] = {};
+			gb_snprintf(worker_name, gb_size_of(worker_name), "%.*s%u", pool->worker_prefix_len, pool->worker_prefix, cast(u16)i);
+			gb_thread_set_name(t, worker_name);
+		}
+		#endif
+	}
+}
+
+void thread_pool_start(ThreadPool *pool) {
+	for (isize i = 0; i < pool->thread_count; i++) {
+		gbThread *t = &pool->threads[i];
+		gb_thread_start(t, worker_thread_internal, pool);
+	}
+}
+
+void thread_pool_join(ThreadPool *pool) {
+	pool->is_running = false;
+
+	gb_semaphore_post(&pool->sem_available, cast(i32)pool->thread_count);
+
+	gb_yield();
+
+	for (isize i = 0; i < pool->thread_count; i++) {
+		gbThread *t = &pool->threads[i];
+		gb_thread_join(t);
+	}
+}
+
+
+void thread_pool_destroy(ThreadPool *pool) {
+	thread_pool_join(pool);
+
+	gb_semaphore_destroy(&pool->sem_available);
+	gb_mutex_destroy(&pool->mutex);
+	gb_free(pool->allocator, pool->threads);
+	pool->thread_count = 0;
+	gb_free(pool->allocator, pool->tasks);
+	pool->task_head = 0;
+	pool->task_tail = 0;
+	pool->task_capacity = 0;
+}
+
+
+void thread_pool_add_task(ThreadPool *pool, WorkerTaskProc *proc, void *data) {
+	gb_mutex_lock(&pool->mutex);
+
+	if (pool->task_tail == pool->task_capacity) {
+		isize new_cap = 2*pool->task_capacity + 8;
+		WorkerTask *new_tasks = gb_alloc_array(pool->allocator, WorkerTask, new_cap);
+		gb_memmove(new_tasks, pool->tasks, (pool->task_tail)*gb_size_of(WorkerTask));
+		pool->tasks = new_tasks;
+		pool->task_capacity = new_cap;
+	}
+	WorkerTask task = {};
+	task.do_work = proc;
+	task.data = data;
+
+	pool->tasks[pool->task_tail++] = task;
+	gb_semaphore_post(&pool->sem_available, 1);
+	gb_mutex_unlock(&pool->mutex);
+}
+
+bool thread_pool_try_and_pop_task(ThreadPool *pool, WorkerTask *task) {
+	bool got_task = false;
+	if (gb_mutex_try_lock(&pool->mutex)) {
+		if (pool->task_tail > pool->task_head) {
+			gb_atomic32_fetch_add(&pool->processing_work_count, +1);
+			*task = pool->tasks[pool->task_head++];
+			got_task = true;
+		}
+		gb_mutex_unlock(&pool->mutex);
+	}
+	return got_task;
+}
+void thread_pool_do_work(ThreadPool *pool, WorkerTask *task) {
+	task->result = task->do_work(task->data);
+	gb_atomic32_fetch_add(&pool->processing_work_count, -1);
+}
+
+void thread_pool_wait_to_process(ThreadPool *pool) {
+	while (pool->task_tail > pool->task_head || gb_atomic32_load(&pool->processing_work_count) != 0) {
+		WorkerTask task = {};
+		if (thread_pool_try_and_pop_task(pool, &task)) {
+			thread_pool_do_work(pool, &task);
+		}
+
+		// Safety-kick
+		if (pool->task_tail > pool->task_head && gb_atomic32_load(&pool->processing_work_count) == 0) {
+			gb_mutex_lock(&pool->mutex);
+			gb_semaphore_post(&pool->sem_available, cast(i32)(pool->task_tail-pool->task_head));
+			gb_mutex_unlock(&pool->mutex);
+		}
+
+		gb_yield();
+	}
+
+	thread_pool_join(pool);
+}
+
+
+GB_THREAD_PROC(worker_thread_internal) {
+	ThreadPool *pool = cast(ThreadPool *)thread->user_data;
+	while (pool->is_running) {
+		gb_semaphore_wait(&pool->sem_available);
+
+		WorkerTask task = {};
+		if (thread_pool_try_and_pop_task(pool, &task)) {
+			thread_pool_do_work(pool, &task);
+		}
+	}
+	// Cascade
+	gb_semaphore_release(&pool->sem_available);
+
+	return 0;
+}
+