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Prevent endless loop in lock cycle detection #1510 #1635

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Prevent endless loop in lock cycle detection #1510 #1635

wants to merge 1 commit into from

Commits on Jun 11, 2022

  1. This change prevents an endless loop in: ReentrantCycleDetectingLock.… 

    …detectPotentialLocksCycle()

Due to how code in ReentrantCycleDetectingLock.lockOrDetectPotentialLocksCycle() is synchronized,
its possible for a thread to both own/hold a lock (according to ReentrantCycleDetectingLock.lockOwnerThread)
and wait on the same lock (according to CycleDetectingLock.lockThreadIsWaitingOn).
In this state, if another thread tries to hold the same lock an endless loop will occur when calling detectPotentialLocksCycle().

With this change detectPotentialLocksCycle() removes the lock owning thread from
ReentrantCycleDetectingLock.lockOwnerThread,
if it detects that "this" lock is both waited on and owned by the same thread.
This prevents the endless loop during cycle detection.

Fix for: google#1510
    @trancexpress
    trancexpress committed Jun 11, 2022
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