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Fix HAL_CleanNotifier race. (#793)

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This race was caused by holding a lock while calling into FRC_ChipObject,
which was waiting for the callback to exit before returning, and our
callback wanted to grab the same lock.
This commit is contained in:
Peter Johnson
2017-11-30 20:45:40 -08:00
committed by GitHub
parent cbd08a1e11
commit 65a044f633
1 changed files with 10 additions and 10 deletions
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20
hal/src/main/native/athena/Notifier.cpp
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@@ -88,7 +88,7 @@ static void alarmCallback(uint32_t, void*) {
}
});
if (closestTrigger != UINT64_MAX) {
if (notifierAlarm && closestTrigger != UINT64_MAX) {
// Simply truncate the hardware trigger time to 32-bit.
notifierAlarm->writeTriggerTime(static_cast<uint32_t>(closestTrigger),
&status);
@@ -156,16 +156,16 @@ void HAL_CleanNotifier(HAL_NotifierHandle notifierHandle, int32_t* status) {
notifier->cond.notify_all();
if (notifierRefCount.fetch_sub(1) == 1) {
std::lock_guard<wpi::mutex> lock(notifierMutex);
// if this was the last notifier, clean up alarm and manager
if (notifierAlarm) {
notifierAlarm->writeEnable(false, status);
notifierAlarm = nullptr;
}
if (notifierManager) {
notifierManager->disable(status);
notifierManager = nullptr;
}
// the notifier can call back into our callback, so don't hold the lock
// here (the atomic fetch_sub will prevent multiple parallel entries
// into this function)
if (notifierAlarm) notifierAlarm->writeEnable(false, status);
if (notifierManager) notifierManager->disable(status);
std::lock_guard<wpi::mutex> lock(notifierMutex);
notifierAlarm = nullptr;
notifierManager = nullptr;
closestTrigger = UINT64_MAX;
}
}