Hello, all ...
I'm experiencing a hang in my app when I do things too quickly. When
I pause the app and examine the callstack, I see this:
#0 0x31467b18 in semaphore_timedwait_signal_trap ()
#1 0x3145e984 in semaphore_timedwait_signal ()
#2 0x3145b104 in _pthread_cond_wait ()
#3 0x3145b260 in pthread_cond_timedwait_relative_np ()
#4 0x348cbd58 in CAGuard::WaitFor ()
#5 0x34909954 in ClientAudioQueue::ServicePendingCallbacks ()
#6 0x34909ab8 in AudioQueueStop ()
#7 0x00014334 in -[AudioStreamer stop] (self=0x895800,
_cmd=0x3018cc44) at /Users/jmzorko/work/root/Magnatune/Classes/
AudioStreamer.m:529
#8 0x00003566 in -[MagnatuneAppDelegate stopStream] (self=0x11cc40,
_cmd=0x18694) at /Users/jmzorko/work/root/Magnatune/Classes/
MagnatuneAppDelegate.m:237
#9 0x0000f8d2 in -[SongController tableView:didSelectRowAtIndexPath:]
(self=0x12e4c0, _cmd=0x300f1a90, tableView=0x186080,
indexPath=0x1491a0) at /Users/jmzorko/work/root/Magnatune/Classes/
SongController.m:212
This is happening inside my observeValueForKeyPath method ...
basically the background thread that does the Core Audio stuff has
been told to stop via AudioQueueStop(), and the IsRunning callback set
the value of a boolean called isPlaying to false. I've registered as
an observer to this boolean, and usually things work well. However,
when I select a new song to play too soon after a previous song,
observeValueForKeyPath seems to hang. Here is observeValueForKeyPath:
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object
change:(NSDictionary *)change
context:(void *)context
{
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
NSLog(@"observeValueForKeyPath -- current thread ID: %x, keypath:
%s", [NSThread currentThread], [keyPath UTF8String]);
if ([keyPath isEqualToString:@"isPlaying"])
{
NSLog(@"calling handleIsPlaying");
[self performSelectorOnMainThread:@selector(handleIsPlaying:)
withObject:keyPath waitUntilDone:YES];
[pool release];
return;
}
.
.
.
[pool release];
[super observeValueForKeyPath:keyPath ofObject:object change:change
context:context];
}
... and here is handleIsPlaying:
- (void)handleIsPlaying:(NSString *)isPlaying
{
NSLog(@"inside handleIsPlaying");
if ([streamer isPlaying])
{
NSLog(@"handleIsPlaying reports that the streamer is currently
playing");
}
else
{
NSLog(@"stopping and releasing audio engine");
[streamer removeObserver:self forKeyPath:@"isPlaying"];
[streamer removeObserver:self forKeyPath:@"failed"];
if (!self.toldAudioStreamerToStop)
{
[streamer removeObserver:self
forKeyPath:@"buffersEmpty"];
}
[streamer release];
//streamer = nil;
NSLog(@"audio engine is released -- streamer not nil yet because
thread might not have stopped yet");
}
NSLog(@"finished handleIsPlaying");
}
... I can't immediately see why handleIsPlaying() or
observeValueForKeyPath() would hang, but according to the callstack,
it's waiting for something. The last thing I see in my console log is:
2008-11-28 06:29:44.459 Magnatune[1357:20b] calling AudioQueueStop()
from AudioStreamer stop method
2008-11-28 06:29:44.990 Magnatune[1357:ba0f] ---------------- audio
queue callback called
2008-11-28 06:29:45.001 Magnatune[1357:ba0f] observeValueForKeyPath --
current thread ID: 1a3860, keypath: isPlaying
2008-11-28 06:29:45.007 Magnatune[1357:ba0f] calling handleIsPlaying
If anyone could illuminate me as to what the problem is (what is
CAGuard supposed to guard against, and why am I running into this
issue?), i'd be very appreciative.
Regards,
John
Falling You - exploring the beauty of voice and sound
http://www.fallingyou.com
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