Deadlock in Mac client (10.6.8)

[michaelrhanson]

I am observing multiple hangs (Application Not Responding / beachball) failures of Mumble on a 2.4Ghz Intel Core 2 Duo iMac running OS 10.6.8.

In the Diagnostic Logs, I observe numerous .hang files. The stack trace appears to implicate a remote AppleScript call during the handling of Log::postNotification, variously called by MainWindow::msgTextMessage, MainWindow::msgUserState, etc.

Specifically, I see postNotification calling qt_mac_execute_apple_script, which works its way down through the OSA and UAS libraries, until it hits AESendMessage, which then goes into a semaphore spin inside sendToModernProcess. The application becomes nonresponsive and has to be force-terminated.

In a few of the .hang reports I can see re-entrant calls to the main loop in my stack, which sounds like it could be a source of deadlock. Specifically, I see MainWindow::msgUserState calling postNotification, working down through AppleScript to UASRemoteSend, then InternalComponentActive, then AEDefaultActiveProc -- which then calls WaitNextEvent, and goes off through the main event dispatch AGAIN on the same stack, and handles a MainWindow::msgTextMessage call, which works down to another AppleScript call. I don't know my way around the Mumble code, but having two calls to WaitNextEvent on the same stack sounds pretty weird to me, and a recipe for deadlocks.

Does this sound like anything somebody knows about? The problem is pretty immediate and fatal -- the client becomes unusable after several minutes, usually.

Thanks.

[michaelrhanson]

Did some more digging: it looks like this code branch is the "GrowlHelperApp" apple event dispatch -- that is, on a pre 10.8 system, Mumble sends notifications to Growl instead of the system notification library.

So: I think I'm finding a deadlock in the Growl message handling on pre-10.8 systems. Anybody else seen that?

[michaelrhanson]

Posted a more detailed analysis and diagnosis here:

https://github.com/mumble-voip/mumble/issues/1152

[michaelrhanson]

Diagnosed as an old version of Growl, and fixed by updating Growl.