[Jack-Devel] Lock recursion in Trylock()

Hi all,
This is the first time I am writing to the list. I am not sure this is the right place to send patches, just let me know if you prefer the use of a different channel.
I am using jack in an embedded linux project, and I have had to analyze a crash dump from a (heavily threaded) client application, which failed on the
Jack_error line in JackPosixMutex.cpp: Trylock().

The cause of this is that jack_error() will call JackMessageBuffer::AddMessage() which will call Trylock(), which, if the lock is held, will call jack_error(), and the wole sequence will repeat until the stack is exhausted.

Below is a patch that simply disables the jack_error call for this case. Is it actually an error to call Trylock() from a different thread? This seems more like a copy-paste remnant from the Lock() function. The jack_error() calls in Lock() and Unlock() are probably not a problem, though they make me a bit uncomfortable as well.

I hope this helps,
Cheers,
Luciano

--- a/posix/JackPosixMutex.cpp
+++ b/posix/JackPosixMutex.cpp
@@ -69,7 +69,10 @@ namespace Jack
                 return false;
             }
         } else {
+           /* Calling jack_error here will recursively call Trylock() if
+            * multithreaded debugging is active.  Don't do that.
             jack_error("JackBasePosixMutex::Trylock mutex already locked by thread = %d", current_thread);
+            */
             return false;
         }
     }





--
Luciano Montanaro
EntryNAV - Audio Software Integrator
Magneti Marelli Electronic Systems
Viale Carlo Emanuele II 150, Venaria Reale (To)
Tel. (+39) 011 6879765




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