Fix deadlock in race condition#294
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Ryan Molden analyzed a deadlock and the docs for `Monitor.Wait` and found that our call that includes a timeout means when the other lock holder takes more than 3 seconds to do its work and call `Monitor.PulseAll` that we'll still get `false` from `Monitor.Wait`. Then when we loop around to `Monitor.Wait` again, it will block for a `PulseAll` that may never recur. The fix is to double-check the state before re-entering the Wait to see if we just missed the `PulseAll` call. If we did, we break out of the loop immediately. I also add more to another code comment discussing thread concerns to make it clearer that it's doing what it is supposed to.
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This fixes devdiv-1357805. |
Codecov Report
@@ Coverage Diff @@
## main #294 +/- ##
==========================================
- Coverage 89.62% 89.55% -0.07%
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Files 87 87
Lines 6053 6111 +58
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+ Hits 5425 5473 +48
- Misses 628 638 +10
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ryanmolden
approved these changes
Jan 31, 2022
milopezc
approved these changes
Jan 31, 2022
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Ryan Molden analyzed a deadlock and the docs for
Monitor.Waitand found that our call that includes a timeout means when the other lock holder takes more than 3 seconds to do its work and callMonitor.PulseAllthat we'll still getfalsefromMonitor.Wait. Then when we loop around toMonitor.Waitagain, it will block for aPulseAllthat may never recur.The fix is to double-check the state before re-entering the Wait to see if we just missed the
PulseAllcall. If we did, we break out of the loop immediately.I also add more to another code comment discussing thread concerns to make it clearer that it's doing what it is supposed to.