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Improve worker thread shutdown.

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Always ensure worker thread task queue is drained before shutting down.
This commit is contained in:
Geza Lore 2022-06-27 14:16:20 +01:00
parent ced39d0982
commit 1bb6433649
2 changed files with 12 additions and 15 deletions
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21
include/verilated_threads.cpp
View File

@ -50,31 +50,26 @@ VlMTaskVertex::VlMTaskVertex(uint32_t upstreamDepCount)
VlWorkerThread::VlWorkerThread(uint32_t threadId, VerilatedContext* contextp,
VlExecutionProfiler* profilerp, VlStartWorkerCb startCb)
: m_ready_size{0}
, m_exiting{false}
, m_cthread{startWorker, this, threadId, profilerp, startCb}
, m_contextp{contextp} {}
VlWorkerThread::~VlWorkerThread() {
m_exiting.store(true, std::memory_order_release);
wakeUp();
shutdown();
// The thread should exit; join it.
m_cthread.join();
}
void VlWorkerThread::shutdownTask(void*, bool) {
// Deliberately empty, we use the address of this function as a magic number
}
void VlWorkerThread::workerLoop() {
ExecRec work;
work.m_fnp = nullptr;
while (true) {
if (VL_LIKELY(!work.m_fnp)) dequeWork(&work);
// Do this here, not above, to avoid a race with the destructor.
if (VL_UNLIKELY(m_exiting.load(std::memory_order_acquire))) break;
if (VL_LIKELY(work.m_fnp)) {
work.m_fnp(work.m_selfp, work.m_evenCycle);
work.m_fnp = nullptr;
}
dequeWork(&work);
if (VL_UNLIKELY(work.m_fnp == shutdownTask)) break;
work.m_fnp(work.m_selfp, work.m_evenCycle);
}
}

6
include/verilated_threads.h
View File

@ -165,7 +165,6 @@ private:
// Store the size atomically, so we can spin wait
std::atomic<size_t> m_ready_size;
std::atomic<bool> m_exiting; // Worker thread should exit
std::thread m_cthread; // Underlying C++ thread record
VerilatedContext* const m_contextp; // Context for spawned thread
@ -198,7 +197,6 @@ public:
m_ready.erase(m_ready.begin());
m_ready_size.fetch_sub(1, std::memory_order_relaxed);
}
inline void wakeUp() { addTask(nullptr, nullptr, false); }
inline void addTask(VlExecFnp fnp, VlSelfP selfp, bool evenCycle)
VL_MT_SAFE_EXCLUDES(m_mutex) {
bool notify;
@ -210,6 +208,10 @@ public:
}
if (notify) m_cv.notify_one();
}
inline void shutdown() { addTask(shutdownTask, nullptr, false); }
static void shutdownTask(void*, bool);
void workerLoop();
static void startWorker(VlWorkerThread* workerp, uint32_t threadId,
VlExecutionProfiler* profilerp, VlStartWorkerCb startCb);