Fix for deadlock issue 1980 #2121
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This unit test fails until we can remove callbacks that are being executed.
This fixes a potential deadlock when a timer is being removed that's also being executed.
fujitatomoya
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Jan 26, 2021
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makes sense to me. I also confirmed that this PR fixes the deadlock problem introduced here.
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@fujitatomoya , is there anything else I can do to help get this issue merged and resolved? |
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@jacobperron @mjcarroll @sloretz friendly ping. |
jacobperron
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Mar 11, 2021
jacobperron
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Apr 6, 2021
* Add unit test for removing a callback that's being executed. This unit test fails until we can remove callbacks that are being executed. * Use the marked_for_removal flag if the callback is being executed. This fixes a potential deadlock when a timer is being removed that's also being executed.
This was referenced Sep 28, 2022
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We encountered the issue sketched in #1980 in a production system last week.
To understand the issue at hand I've made a minimal-non-working example here. Looking at the source code it seems that the callback queue is actually at fault, not the timer code. The
removeByIDdeadlocks when a callback by that id is currently being executed.The first commit introduces a unit test that demonstrates this deadlock in a unit test.
The second commit is the proposed fix for this problem. We try to obtain the lock, if we fail to obtain the lock we defer removal until the next callback queue cycle using the already existing
marked_for_removalboolean.FYI @guillaumeautran , @mikepurvis , @jasonimercer