Fix CoreJob race condition #1027
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jdonald
reviewed
Oct 28, 2017
| @@ -52,8 +52,10 @@ void CoreJob::OnPended(std::unique_lock<std::mutex>&& lk){ | |||
| // Need to ask the thread pool to handle our events again: | |||
| m_curEventInTeardown = false; | |||
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| if (m_curEvent) | |||
| delete static_cast<std::future<void>*>(m_curEvent); | |||
| std::future<void>* future = static_cast<std::future<void>*>(std::atomic_exchange<void*>(&m_curEvent, nullptr)); | |||
jdonald
approved these changes
Oct 28, 2017
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It was possible for current event handler to be deleted twice, and also for it to inadvertently be started multiple times, causing a few user functions to be run in different threads.
One of the main issues was that, although
CoreJob'sOnPendedfunction expected a lock, two different locks were being passed from different threads to the function, nullifying exclusivity. Also, thewaitfunctions could be called from different threads, potentially causing a double free.A test (
CoreJobTest.PendFromMultipleThreads) has been added, but it doesn't fail every time without this fix. To see the failure case, the test should be repeated multiple times (using--gtest_repeat, specifying the number of runs, and--gtest_throw_on_failure, to stop on failure).