[jira] [Created] (IMPALA-14433) Deadlock in OpenTelemetry Tracing Code

["Jason Fehr (Jira)" <ji...@apache.org>]

Jason Fehr created IMPALA-14433:
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             Summary: Deadlock in OpenTelemetry Tracing Code
                 Key: IMPALA-14433
                 URL: https://issues.apache.org/jira/browse/IMPALA-14433
             Project: IMPALA
          Issue Type: Bug
    Affects Versions: Impala 5.0.0
            Reporter: Jason Fehr
            Assignee: Jason Fehr


All functions in the SpanManager class operate under the assumption that child_span_mu_ in the SpanManager class will be locked before the ClientRequestState lock. However, the ImpalaServer::ExecuteInternal function takes the ClientRequestState lock before calling SpanManager::EndChildSpanPlanning.

Simplified Explanation:
1. Thread 1 -- ImpalaServer::ExecuteInternal takes ClientRequestState lock
2. Thread 2 -- a SpanManager function (such as StartChildSpanClose) locks child_span_mu_
3. Thread 2 -- attempts to take ClientRequestState lock, waits because Thread 1 owns that lock
4. Thread 1 --  ImpalaServer::ExecuteInternal calls SpanManager::EndChildSpanPlanning
5. Thread 1 -- attempts to take child_span_mu_ lock but waits because Thread 2 owns that lock

Detailed Explanation:
The deadlock happens when another function (such as StartChildSpanClose) is called after ImpalaServer::ExecuteInternal has taken a lock on the ClientRequestState lock but before that same function calls SpanManager::EndChildSpanPlanning.  In this case, the other function takes a lock on child_span_mu_ followed by trying to take the ClientRequestState lock.  Since ImpalaServer::ExecuteInternal already holds that lock, the other function waits.  Then, when ImpalaServer::ExecuteInternal calls SpanManager::EndChildSpanPlanning, it tries to lock child_span_mu_ which is already held.



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