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Internals: Fix unbalanced V3LockGuard locking (#4193)

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This commit is contained in:
Mariusz Glebocki
2023-05-13 10:32:33 -04:00
committed by GitHub
parent be429a5800
commit 949be301de
9 changed files with 58 additions and 75 deletions
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src/V3ThreadPool.cpp
+38 -32
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@@ -23,29 +23,33 @@
// c++11 requires definition of static constexpr as well as declaration
constexpr unsigned int V3ThreadPool::FUTUREWAITFOR_MS;
void V3ThreadPool::resize(unsigned n) VL_MT_UNSAFE {
void V3ThreadPool::resize(unsigned n) VL_MT_UNSAFE VL_EXCLUDES(m_mutex)
VL_EXCLUDES(m_stoppedJobsMutex) {
// This function is not thread-safe and can result in race between threads
UASSERT(V3MutexConfig::s().lockConfig(),
"Mutex config needs to be locked before starting ThreadPool");
V3LockGuard lock{m_mutex};
V3LockGuard stoppedJobsLock{m_stoppedJobsMutex};
UASSERT(m_queue.empty(), "Resizing busy thread pool");
// Shut down old threads
m_shutdown = true;
m_stoppedJobs = 0;
m_cv.notify_all();
m_stoppedJobsCV.notify_all();
stoppedJobsLock.unlock();
lock.unlock();
{
V3LockGuard lock{m_mutex};
V3LockGuard stoppedJobsLock{m_stoppedJobsMutex};
UASSERT(m_queue.empty(), "Resizing busy thread pool");
// Shut down old threads
m_shutdown = true;
m_stoppedJobs = 0;
m_cv.notify_all();
m_stoppedJobsCV.notify_all();
}
while (!m_workers.empty()) {
m_workers.front().join();
m_workers.pop_front();
}
lock.lock();
// Start new threads
m_shutdown = false;
for (unsigned int i = 1; i < n; ++i) {
m_workers.emplace_back(&V3ThreadPool::startWorker, this, i);
if (n > 1) {
V3LockGuard lock{m_mutex};
// Start new threads
m_shutdown = false;
for (unsigned int i = 1; i < n; ++i) {
m_workers.emplace_back(&V3ThreadPool::startWorker, this, i);
}
}
}
@@ -60,7 +64,7 @@ void V3ThreadPool::workerJobLoop(int id) VL_MT_SAFE {
job_t job;
{
V3LockGuard lock(m_mutex);
m_cv.wait(lock, [&]() VL_REQUIRES(m_mutex) {
m_cv.wait(m_mutex, [&]() VL_REQUIRES(m_mutex) {
return !m_queue.empty() || m_shutdown || m_stopRequested;
});
if (m_shutdown) return; // Terminate if requested
@@ -100,9 +104,9 @@ void V3ThreadPool::requestExclusiveAccess(const V3ThreadPool::job_t&& exclusiveA
V3LockGuard stoppedJobLock{m_stoppedJobsMutex};
// if some other job already requested exclusive access
// wait until it stops
if (stopRequested()) { waitStopRequested(stoppedJobLock); }
if (stopRequested()) { waitStopRequested(); }
m_stopRequested = true;
waitOtherThreads(stoppedJobLock);
waitOtherThreads();
m_exclusiveAccess = true;
exclusiveAccessJob();
m_exclusiveAccess = false;
@@ -114,25 +118,26 @@ void V3ThreadPool::requestExclusiveAccess(const V3ThreadPool::job_t&& exclusiveA
bool V3ThreadPool::waitIfStopRequested() VL_MT_SAFE {
V3LockGuard stoppedJobLock(m_stoppedJobsMutex);
if (!stopRequested()) return false;
waitStopRequested(stoppedJobLock);
waitStopRequested();
return true;
}
void V3ThreadPool::waitStopRequested(V3LockGuard& stoppedJobLock) VL_REQUIRES(m_stoppedJobsMutex) {
void V3ThreadPool::waitStopRequested() VL_REQUIRES(m_stoppedJobsMutex) {
++m_stoppedJobs;
m_stoppedJobsCV.notify_all();
m_stoppedJobsCV.wait(
stoppedJobLock, [&]() VL_REQUIRES(m_stoppedJobsMutex) { return !m_stopRequested.load(); });
m_stoppedJobsCV.wait(m_stoppedJobsMutex, [&]() VL_REQUIRES(m_stoppedJobsMutex) {
return !m_stopRequested.load();
});
--m_stoppedJobs;
m_stoppedJobsCV.notify_all();
}
void V3ThreadPool::waitOtherThreads(V3LockGuard& stoppedJobLock) VL_MT_SAFE_EXCLUDES(m_mutex)
void V3ThreadPool::waitOtherThreads() VL_MT_SAFE_EXCLUDES(m_mutex)
VL_REQUIRES(m_stoppedJobsMutex) {
++m_stoppedJobs;
m_stoppedJobsCV.notify_all();
m_cv.notify_all();
m_stoppedJobsCV.wait(stoppedJobLock, [&]() VL_REQUIRES(m_stoppedJobsMutex) {
m_stoppedJobsCV.wait(m_stoppedJobsMutex, [&]() VL_REQUIRES(m_stoppedJobsMutex) {
// count also the main thread
return m_stoppedJobs == (m_workers.size() + 1);
});
@@ -152,19 +157,20 @@ void V3ThreadPool::selfTest() {
});
};
auto secondJob = [&](int sleep) -> void {
V3LockGuard lock{commonMutex};
lock.unlock();
commonMutex.lock();
commonMutex.unlock();
s().waitIfStopRequested();
lock.lock();
V3LockGuard lock{commonMutex};
std::this_thread::sleep_for(std::chrono::milliseconds{sleep});
commonValue = 1000;
};
auto thirdJob = [&](int sleep) -> void {
V3LockGuard lock{commonMutex};
std::this_thread::sleep_for(std::chrono::milliseconds{sleep});
lock.unlock();
{
V3LockGuard lock{commonMutex};
std::this_thread::sleep_for(std::chrono::milliseconds{sleep});
}
s().requestExclusiveAccess([&]() { firstJob(sleep); });
lock.lock();
V3LockGuard lock{commonMutex};
commonValue = 1000;
};
std::list<std::future<void>> futures;