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handle steal-fail vs steal-empty

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This commit is contained in:
Colin Davidson
2024-07-14 00:29:58 -07:00
parent cdede4928c
commit 4420128dc1
1 changed files with 24 additions and 12 deletions
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36
src/thread_pool.cpp
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@@ -10,6 +10,12 @@ gb_internal void thread_pool_destroy(ThreadPool *pool);
gb_internal bool thread_pool_add_task(ThreadPool *pool, WorkerTaskProc *proc, void *data);
gb_internal void thread_pool_wait(ThreadPool *pool);
enum GrabState {
GrabSuccess = 0,
GrabEmpty = 1,
GrabFailed = 2,
};
struct ThreadPool {
gbAllocator threads_allocator;
Slice<Thread> threads;
@@ -82,7 +88,7 @@ void thread_pool_queue_push(Thread *thread, WorkerTask task) {
futex_broadcast(&thread->pool->tasks_available);
}
bool thread_pool_queue_take(Thread *thread, WorkerTask *task) {
GrabState thread_pool_queue_take(Thread *thread, WorkerTask *task) {
ssize_t bot = thread->queue.bottom.load(std::memory_order_relaxed) - 1;
TaskRingBuffer *cur_ring = thread->queue.ring.load(std::memory_order_relaxed);
thread->queue.bottom.store(bot, std::memory_order_relaxed);
@@ -98,28 +104,28 @@ bool thread_pool_queue_take(Thread *thread, WorkerTask *task) {
if (!thread->queue.top.compare_exchange_strong(top, top + 1, std::memory_order_seq_cst, std::memory_order_relaxed)) {
// Race failed
thread->queue.bottom.store(bot + 1, std::memory_order_relaxed);
return false;
return GrabEmpty;
}
thread->queue.bottom.store(bot + 1, std::memory_order_relaxed);
return true;
return GrabSuccess;
}
// We got a task without hitting a race
return true;
return GrabSuccess;
} else {
// Queue is empty
thread->queue.bottom.store(bot + 1, std::memory_order_relaxed);
return false;
return GrabEmpty;
}
}
bool thread_pool_queue_steal(Thread *thread, WorkerTask *task) {
GrabState thread_pool_queue_steal(Thread *thread, WorkerTask *task) {
ssize_t top = thread->queue.top.load(std::memory_order_acquire);
std::atomic_thread_fence(std::memory_order_seq_cst);
ssize_t bot = thread->queue.bottom.load(std::memory_order_acquire);
bool ret = false;
GrabState ret = GrabEmpty;
if (top < bot) {
// Queue is not empty
TaskRingBuffer *cur_ring = thread->queue.ring.load(std::memory_order_consume);
@@ -127,9 +133,9 @@ bool thread_pool_queue_steal(Thread *thread, WorkerTask *task) {
if (!thread->queue.top.compare_exchange_strong(top, top + 1, std::memory_order_seq_cst, std::memory_order_relaxed)) {
// Race failed
ret = false;
ret = GrabFailed;
} else {
ret = true;
ret = GrabSuccess;
}
}
return ret;
@@ -149,7 +155,7 @@ gb_internal void thread_pool_wait(ThreadPool *pool) {
while (pool->tasks_left.load(std::memory_order_acquire)) {
// if we've got tasks on our queue, run them
while (thread_pool_queue_take(current_thread, &task)) {
while (!thread_pool_queue_take(current_thread, &task)) {
task.do_work(task.data);
pool->tasks_left.fetch_sub(1, std::memory_order_release);
}
@@ -178,7 +184,7 @@ gb_internal THREAD_PROC(thread_pool_thread_proc) {
usize finished_tasks = 0;
i32 state;
while (thread_pool_queue_take(current_thread, &task)) {
while (!thread_pool_queue_take(current_thread, &task)) {
task.do_work(task.data);
pool->tasks_left.fetch_sub(1, std::memory_order_release);
@@ -200,7 +206,13 @@ gb_internal THREAD_PROC(thread_pool_thread_proc) {
Thread *thread = &pool->threads.data[idx];
WorkerTask task;
if (thread_pool_queue_steal(thread, &task)) {
GrabState ret = thread_pool_queue_steal(thread, &task);
if (ret == GrabFailed) {
goto main_loop_continue;
} else if (ret == GrabEmpty) {
continue;
} else if (ret == GrabSuccess) {
task.do_work(task.data);
pool->tasks_left.fetch_sub(1, std::memory_order_release);