diff --git a/automotive/vehicle/aidl/impl/utils/common/include/RecurrentTimer.h b/automotive/vehicle/aidl/impl/utils/common/include/RecurrentTimer.h index 5f0f7161c2..cd2b72713c 100644 --- a/automotive/vehicle/aidl/impl/utils/common/include/RecurrentTimer.h +++ b/automotive/vehicle/aidl/impl/utils/common/include/RecurrentTimer.h @@ -83,8 +83,9 @@ class RecurrentTimer final { // each time we might introduce outdated elements to the top. We must make sure the heap is // always valid from the top. void removeInvalidCallbackLocked() REQUIRES(mLock); - // Pops the next closest callback (must be valid) from the heap. - std::unique_ptr popNextCallbackLocked() REQUIRES(mLock); + // Gets the next calblack to run (must be valid) from the heap, update its nextTime and put + // it back to the heap. + std::shared_ptr getNextCallbackLocked(int64_t now) REQUIRES(mLock); }; } // namespace vehicle diff --git a/automotive/vehicle/aidl/impl/utils/common/src/RecurrentTimer.cpp b/automotive/vehicle/aidl/impl/utils/common/src/RecurrentTimer.cpp index 43f5d69467..c6d3687553 100644 --- a/automotive/vehicle/aidl/impl/utils/common/src/RecurrentTimer.cpp +++ b/automotive/vehicle/aidl/impl/utils/common/src/RecurrentTimer.cpp @@ -103,68 +103,71 @@ void RecurrentTimer::removeInvalidCallbackLocked() { } } -std::unique_ptr RecurrentTimer::popNextCallbackLocked() { +std::shared_ptr RecurrentTimer::getNextCallbackLocked(int64_t now) { std::pop_heap(mCallbackQueue.begin(), mCallbackQueue.end(), CallbackInfo::cmp); - std::unique_ptr info = std::move(mCallbackQueue[mCallbackQueue.size() - 1]); - mCallbackQueue.pop_back(); + auto& callbackInfo = mCallbackQueue[mCallbackQueue.size() - 1]; + auto nextCallback = callbackInfo->callback; + // intervalCount is the number of interval we have to advance until we pass now. + size_t intervalCount = (now - callbackInfo->nextTime) / callbackInfo->interval + 1; + callbackInfo->nextTime += intervalCount * callbackInfo->interval; + std::push_heap(mCallbackQueue.begin(), mCallbackQueue.end(), CallbackInfo::cmp); + // Make sure the first element is always valid. removeInvalidCallbackLocked(); - return info; + + return nextCallback; } void RecurrentTimer::loop() { - std::unique_lock uniqueLock(mLock); - + std::vector> callbacksToRun; while (true) { - // Wait until the timer exits or we have at least one recurrent callback. - mCond.wait(uniqueLock, [this] { - ScopedLockAssertion lockAssertion(mLock); - return mStopRequested || mCallbackQueue.size() != 0; - }); - - int64_t interval; { + std::unique_lock uniqueLock(mLock); ScopedLockAssertion lockAssertion(mLock); + // Wait until the timer exits or we have at least one recurrent callback. + mCond.wait(uniqueLock, [this] { + ScopedLockAssertion lockAssertion(mLock); + return mStopRequested || mCallbackQueue.size() != 0; + }); + + int64_t interval; if (mStopRequested) { return; } // The first element is the nearest next event. int64_t nextTime = mCallbackQueue[0]->nextTime; int64_t now = uptimeNanos(); + if (nextTime > now) { interval = nextTime - now; } else { interval = 0; } - } - // Wait for the next event or the timer exits. - if (mCond.wait_for(uniqueLock, std::chrono::nanoseconds(interval), [this] { - ScopedLockAssertion lockAssertion(mLock); - return mStopRequested; - })) { - return; - } + // Wait for the next event or the timer exits. + if (mCond.wait_for(uniqueLock, std::chrono::nanoseconds(interval), [this] { + ScopedLockAssertion lockAssertion(mLock); + return mStopRequested; + })) { + return; + } - { - ScopedLockAssertion lockAssertion(mLock); - int64_t now = uptimeNanos(); + now = uptimeNanos(); + callbacksToRun.clear(); while (mCallbackQueue.size() > 0) { int64_t nextTime = mCallbackQueue[0]->nextTime; if (nextTime > now) { break; } - std::unique_ptr info = popNextCallbackLocked(); - info->nextTime += info->interval; - - auto callback = info->callback; - mCallbackQueue.push_back(std::move(info)); - std::push_heap(mCallbackQueue.begin(), mCallbackQueue.end(), CallbackInfo::cmp); - - (*callback)(); + callbacksToRun.push_back(getNextCallbackLocked(now)); } } + + // Do not execute the callback while holding the lock. + for (size_t i = 0; i < callbacksToRun.size(); i++) { + (*callbacksToRun[i])(); + } } } diff --git a/automotive/vehicle/aidl/impl/utils/common/test/RecurrentTimerTest.cpp b/automotive/vehicle/aidl/impl/utils/common/test/RecurrentTimerTest.cpp index a033a248cd..141efc135b 100644 --- a/automotive/vehicle/aidl/impl/utils/common/test/RecurrentTimerTest.cpp +++ b/automotive/vehicle/aidl/impl/utils/common/test/RecurrentTimerTest.cpp @@ -186,6 +186,33 @@ TEST_F(RecurrentTimerTest, testRegisterSameCallbackMultipleTimes) { ASSERT_EQ(countTimerCallbackQueue(&timer), static_cast(0)); } +TEST_F(RecurrentTimerTest, testRegisterCallbackMultipleTimesNoDeadLock) { + // We want to avoid the following situation: + // Caller holds a lock while calling registerTimerCallback, registerTimerCallback will try + // to obtain an internal lock inside timer. + // Meanwhile an recurrent action happens with timer holding an internal lock. The action + // tries to obtain the lock currently hold by the caller. + // The solution is that while calling recurrent actions, timer must not hold the internal lock. + + std::unique_ptr timer = std::make_unique(); + std::mutex lock; + for (size_t i = 0; i < 1000; i++) { + std::scoped_lock lockGuard(lock); + auto action = std::make_shared([&lock] { + // While calling this function, the timer must not hold lock in order not to dead + // lock. + std::scoped_lock lockGuard(lock); + }); + // 10ms + int64_t interval = 10'000'000; + timer->registerTimerCallback(interval, action); + // Sleep for a little while to let the recurrent actions begin. + std::this_thread::sleep_for(std::chrono::milliseconds(1)); + } + // Make sure we stop the timer before we destroy lock. + timer.reset(); +} + } // namespace vehicle } // namespace automotive } // namespace hardware