Fix #807: recv wait can deadlock on an application thread #808
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Thanks! Great catch. Will try to get this landed on Monday, in time for 16.4.4. |
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Just pushed some changes to try a slightly simpler approach, without thread-local storage. Also pushed some style fixes/tweaks. I'll have to get some sleep now, so I'll land this first thing tomorrow -- but in case you get a chance to test in the meantime please let me know how it goes :) |
oleavr
approved these changes
Jul 16, 2024
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Super. Agreed this is simpler and solves the deadlock, I was able to confirm in testing as well. Thx! |
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This is a fix for #807 : recv wait can deadlock on an application thread.
See the issue description for a discussion of the root cause.
The proposed fix here operates by introducing a thread-local variable,
event_count_last_seen. After entering the mutex, which ensures a stable reading ofcore->event_count, the thread enters the wait forevent_condonly ifcore->event_countis equal toevent_count_last_seen. In this way, we can guarantee that we won't begin waiting onevent_condat a time when the event we need has already been broadcast, which would produce the deadlock.