[asterisk-bugs] [JIRA] (ASTERISK-24614) Deadlock when DEBUG_THREADS compiler flag enabled

[Richard Mudgett (JIRA)]

Richard Mudgett created ASTERISK-24614:
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             Summary: Deadlock when DEBUG_THREADS compiler flag enabled
                 Key: ASTERISK-24614
                 URL: https://issues.asterisk.org/jira/browse/ASTERISK-24614
             Project: Asterisk
          Issue Type: Bug
      Security Level: None
          Components: Core/General
    Affects Versions: 13.0.2, 12.7.2, 11.14.2, 1.8.32.1
            Reporter: Richard Mudgett


There is a sporadical strange deadlock in where Certified Asterisk 1.8.28-cert2 is running with DEBUG_TRHEADS compiler flag enabled.
In the backtrace log you will find thread 49 waiting for the reentrancy mutex which seems not to get unlocked by thread 7.

When using Certified Asterisk 1.8.15-cert6 (DEBUG_THREADS enabled) instead this deadlock does not occur.

After a look into the source code, it is most likely the changes of ASTERISK-22455 are responsible for this deadlock. In lock.c / int __ast_cond_wait() a pthread_mutex is copied which leads to undefined results since pthread_mutex is an opaque type.

{noformat}
...
	} else if (t->tracking) {
  		pthread_mutex_t reentr_mutex_orig;
 		ast_reentrancy_lock(lt);
		 /* Restore lock tracking to what it was prior to the wait */
 		reentr_mutex_orig = lt->reentr_mutex;
 		*lt = lt_orig;
 		/* un-trash the mutex we just copied over */
 		lt->reentr_mutex = reentr_mutex_orig;
 		ast_reentrancy_unlock(lt);
 
		 ast_restore_lock_info(t);
	 }
...
{noformat}

Thanks to Thomas Airmont for finding this obscure regression in the DEBUG_THREADS code.



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