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[SYCL] Avoid overuse of CPU on wait read-write lock loop #2525

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merged 3 commits into from
Sep 24, 2020
Merged

[SYCL] Avoid overuse of CPU on wait read-write lock loop #2525

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b0fc609
[SYCL] Avoid overuse of CPU on wait mutex loop
vladimirlaz Sep 23, 2020
fa932e7
[SYCL] revert unnecessary change
vladimirlaz Sep 23, 2020
e13fd3c
[SYCL] add comment describing change
vladimirlaz Sep 24, 2020
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13 changes: 7 additions & 6 deletions sycl/source/detail/scheduler/scheduler.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -12,9 +12,11 @@
#include <detail/scheduler/scheduler.hpp>
#include <detail/stream_impl.hpp>

#include <chrono>
#include <memory>
#include <mutex>
#include <set>
#include <thread>
#include <vector>

__SYCL_INLINE_NAMESPACE(cl) {
Expand Down Expand Up @@ -153,11 +155,9 @@ void Scheduler::waitForEvent(EventImplPtr Event) {
}

void Scheduler::cleanupFinishedCommands(EventImplPtr FinishedEvent) {
// Avoiding deadlock situation, where one thread is in the process of
// enqueueing (with a locked mutex) a currently blocked task that waits for
// another thread which is stuck at attempting cleanup.
std::unique_lock<std::shared_timed_mutex> Lock(MGraphLock, std::try_to_lock);
if (Lock.owns_lock()) {
std::unique_lock<std::shared_timed_mutex> Lock(MGraphLock, std::defer_lock);
{
lockSharedTimedMutex(Lock);
Command *FinishedCmd = static_cast<Command *>(FinishedEvent->getCommand());
// The command might have been cleaned up (and set to nullptr) by another
// thread
Expand Down Expand Up @@ -268,7 +268,8 @@ void Scheduler::lockSharedTimedMutex(
// TODO: after switching to C++17, change std::shared_timed_mutex to
// std::shared_mutex and use std::lock_guard here both for Windows and Linux.
while (!Lock.owns_lock()) {
Lock.try_lock();
Lock.try_lock_for(std::chrono::milliseconds(10));
std::this_thread::yield();
}
#else
// It is a deadlock on UNIX in implementation of lock and lock_shared, if
Expand Down