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WorkerThreadPool: Avoid deadlocks when CommandQueueMT is involved

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This commit lets CommandQueueMT play nicely with the WorkerThreadPool to avoid
non-progressable situations caused by an interdependence between both. While a
command queue is being flushed, it allows the WTP to release its lock while tasks
are being awaited so they can make progress in case they need in turn to post
to the command queue.
This commit is contained in:
Pedro J. Estébanez
2023-12-29 01:27:17 +01:00
parent 9444d297ed
commit ae418f9469
3 changed files with 63 additions and 16 deletions
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28
core/object/worker_thread_pool.cpp
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@@ -33,6 +33,7 @@
#include "core/object/script_language.h"
#include "core/os/os.h"
#include "core/os/thread_safe.h"
#include "core/templates/command_queue_mt.h"
void WorkerThreadPool::Task::free_template_userdata() {
ERR_FAIL_NULL(template_userdata);
@@ -43,6 +44,8 @@ void WorkerThreadPool::Task::free_template_userdata() {
WorkerThreadPool *WorkerThreadPool::singleton = nullptr;
thread_local CommandQueueMT *WorkerThreadPool::flushing_cmd_queue = nullptr;
void WorkerThreadPool::_process_task(Task *p_task) {
int pool_thread_index = thread_ids[Thread::get_caller_id()];
ThreadData &curr_thread = threads[pool_thread_index];
@@ -428,7 +431,15 @@ Error WorkerThreadPool::wait_for_task_completion(TaskID p_task_id) {
if (!task_to_process) {
caller_pool_thread->awaited_task = task;
if (flushing_cmd_queue) {
flushing_cmd_queue->unlock();
}
caller_pool_thread->cond_var.wait(lock);
if (flushing_cmd_queue) {
flushing_cmd_queue->lock();
}
DEV_ASSERT(exit_threads || caller_pool_thread->signaled || task->completed);
caller_pool_thread->awaited_task = nullptr;
}
@@ -540,7 +551,14 @@ void WorkerThreadPool::wait_for_group_task_completion(GroupID p_group) {
{
Group *group = *groupp;
if (flushing_cmd_queue) {
flushing_cmd_queue->unlock();
}
group->done_semaphore.wait();
if (flushing_cmd_queue) {
flushing_cmd_queue->lock();
}
uint32_t max_users = group->tasks_used + 1; // Add 1 because the thread waiting for it is also user. Read before to avoid another thread freeing task after increment.
uint32_t finished_users = group->finished.increment(); // fetch happens before inc, so increment later.
@@ -563,6 +581,16 @@ int WorkerThreadPool::get_thread_index() {
return singleton->thread_ids.has(tid) ? singleton->thread_ids[tid] : -1;
}
void WorkerThreadPool::thread_enter_command_queue_mt_flush(CommandQueueMT *p_queue) {
ERR_FAIL_COND(flushing_cmd_queue != nullptr);
flushing_cmd_queue = p_queue;
}
void WorkerThreadPool::thread_exit_command_queue_mt_flush() {
ERR_FAIL_NULL(flushing_cmd_queue);
flushing_cmd_queue = nullptr;
}
void WorkerThreadPool::init(int p_thread_count, float p_low_priority_task_ratio) {
ERR_FAIL_COND(threads.size() > 0);
if (p_thread_count < 0) {