Transfer - Remove recursive locks in snapshot node #1004
Merged
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In the given situation, a deadlock could potentially arise. Let's look at the nodes A, B, and C:
Thread 1:
convertToWrapper ->
acquired lock on A
-> convertToWrapper ->acquired lock on B
-> convertToWrapper ->Attempt to acquire lock on C
Thread 2:
CheckCompleted -> setCompleted ->
acquired lock on C
-> CheckCompleted -> setCompleted ->Attempt to acquire lock on B
Both Thread 1 and Thread 2 find themselves in a state of mutual waiting. Thread 1 is waiting for the mutex of C, which is held by Thread 2, while Thread 2 is waiting for the mutex of B, which is held by Thread 1.
The solution is to ensure that each thread never holds more than one mutex at a time.
Proofs from the logs - Deadlock of 680 minutes
Proof for thread 1's scenario:
Proof for thread 2's scenario: