Pause BIF timers when a process is suspended #10619
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Summary: Bug 1: missing locking of ERTS_PROC_LOCK_BTM (held on some paths but not all) Bug 2: used the scheduler id of the receiver process rather than that of the timer, the two could differ if for example the receiver moved after the creation of the process Bug 3: wrong assertion that timeout is always >0 (sometimes =0 and in that case it will just trigger right after resume) Test Plan: Manual testing on world_e2e_SUITE, putting breakpoints and verifying that both suspend and resume work. Reviewers: Subscribers: Tasks: Tags:
Based on a suggestion by Daniel Gorin, I added a test that creates hundreds of processes and timers, and tries to trigger any race condition that might occur around suspend and resume.
When suspending a process we pause all bif timers targeting it. But until this diff we did not pause any bif timer created after the suspension. Which is an issue for the debugger, as suspending all the processes is not atomic, so new timers can keep appearing even as we're in the middle of suspending processes. This makes the test adding in the last commit pass (it was consistently failing before).
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CT Test Results 3 files 135 suites 49m 3s ⏱️ Results for commit 33601e7. ♻️ This comment has been updated with latest results. To speed up review, make sure that you have read Contributing to Erlang/OTP and that all checks pass. See the TESTING and DEVELOPMENT HowTo guides for details about how to run test locally. Artifacts
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When
erlang:suspend_process()is called, we now pause BIF timers in addition to the process timer. This allows step-debuggers like edb to prevent more spurious timeouts while stopping the world.NB. This handles only timers set by PID, those set by registered name are currently not paused