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// thread_pool.cpp
#define WORKER_TASK_PROC(name) isize name(void *data)
typedef WORKER_TASK_PROC(WorkerTaskProc);
struct WorkerTask {
WorkerTask *next_task;
WorkerTaskProc *do_work;
void *data;
};
struct ThreadPool {
std::atomic<isize> outstanding_task_count;
WorkerTask *volatile next_task;
BlockingMutex task_list_mutex;
isize thread_count;
};
void thread_pool_thread_entry(ThreadPool *pool) {
while (pool->outstanding_task_count) {
if (!pool->next_task) {
yield(); // No need to grab the mutex.
} else {
mutex_lock(&pool->task_list_mutex);
if (pool->next_task) {
WorkerTask *task = pool->next_task;
pool->next_task = task->next_task;
mutex_unlock(&pool->task_list_mutex);
task->do_work(task->data);
pool->outstanding_task_count.fetch_sub(1);
gb_free(heap_allocator(), task);
} else {
mutex_unlock(&pool->task_list_mutex);
}
}
}
}
#if defined(GB_SYSTEM_WINDOWS)
DWORD __stdcall thread_pool_thread_entry_platform(void *arg) {
thread_pool_thread_entry((ThreadPool *) arg);
return 0;
}
void thread_pool_start_thread(ThreadPool *pool) {
CloseHandle(CreateThread(NULL, 0, thread_pool_thread_entry_platform, pool, 0, NULL));
}
#else
void *thread_pool_thread_entry_platform(void *arg) {
thread_pool_thread_entry((ThreadPool *) arg);
return NULL;
}
void thread_pool_start_thread(ThreadPool *pool) {
pthread_t handle;
pthread_create(&handle, NULL, thread_pool_thread_entry_platform, pool);
pthread_detach(handle);
}
#endif
void thread_pool_init(ThreadPool *pool, gbAllocator const &a, isize thread_count, char const *worker_prefix) {
memset(pool, 0, sizeof(ThreadPool));
mutex_init(&pool->task_list_mutex);
pool->outstanding_task_count.store(1);
pool->thread_count = thread_count;
}
void thread_pool_destroy(ThreadPool *pool) {
mutex_destroy(&pool->task_list_mutex);
}
void thread_pool_wait(ThreadPool *pool) {
for (int i = 0; i < pool->thread_count; i++) {
thread_pool_start_thread(pool);
}
pool->outstanding_task_count.fetch_sub(1);
thread_pool_thread_entry(pool);
}
void thread_pool_add_task(ThreadPool *pool, WorkerTaskProc *proc, void *data) {
WorkerTask *task = gb_alloc_item(heap_allocator(), WorkerTask);
task->do_work = proc;
task->data = data;
mutex_lock(&pool->task_list_mutex);
task->next_task = pool->next_task;
pool->next_task = task;
pool->outstanding_task_count.fetch_add(1);
mutex_unlock(&pool->task_list_mutex);
}
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