From 0639ffcfb52c86722fc718fc854ce0818711fc34 Mon Sep 17 00:00:00 2001
From: Silent <zdanio95@gmail.com>
Date: Sat, 10 Aug 2019 19:38:22 +0200
Subject: [PATCH] Handle spurious wakeups on worker thread condition variables
 properly

---
 ext/native/thread/threadpool.cpp | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/ext/native/thread/threadpool.cpp b/ext/native/thread/threadpool.cpp
index f821fc121d..cdb3db217a 100644
--- a/ext/native/thread/threadpool.cpp
+++ b/ext/native/thread/threadpool.cpp
@@ -27,7 +27,7 @@ void WorkerThread::Process(std::function<void()> work) {
 
 void WorkerThread::WaitForCompletion() {
 	std::unique_lock<std::mutex> guard(doneMutex);
-	if (jobsDone < jobsTarget) {
+	while (jobsDone < jobsTarget) {
 		done.wait(guard);
 	}
 }
@@ -37,7 +37,11 @@ void WorkerThread::WorkFunc() {
 	std::unique_lock<std::mutex> guard(mutex);
 	started = true;
 	while (active) {
-		signal.wait(guard);
+		// 'active == false' is one of the conditions for signaling,
+		// do not "optimize" it
+		while (active && jobsTarget <= jobsDone) {
+			signal.wait(guard);
+		}
 		if (active) {
 			work_();
 			doneMutex.lock();
@@ -67,7 +71,11 @@ void LoopWorkerThread::WorkFunc() {
 	std::unique_lock<std::mutex> guard(mutex);
 	started = true;
 	while (active) {
-		signal.wait(guard);
+		// 'active == false' is one of the conditions for signaling,
+		// do not "optimize" it
+		while (active && jobsTarget <= jobsDone) {
+			signal.wait(guard);
+		}
 		if (active) {
 			work_(start_, end_);
 			doneMutex.lock();