(sent again because it was too long and got held for moderation)
Dear list,
Forgive my potential use of bad terminology and ignorance here. I'm about to
talk about concurrency in the context of core data, and I suspect I'm doing
things terribly wrong.
I have an app which does background processing of the entities in a core data
stack of an NSPersistentDocument . Sometimes I get deadlocks (I think) which,
when sampled, look like the excerpt below.
Roughly, what my app does is:
1) When a File entity is created, it creates for itself a MetaData collector
2) The MetaData collector has a timer which fires every second
3) In the timer selector, if a update is no in process, I do:
a) create a new MetaDataOperation (NSOperation subclass)
- the completion block of this operation tries to post a
notification on the main thread like this
dispatch_sync(dispatch_get_main_queue(), ^{
[blockSelf notifyOfUpdate];
blockSelf = nil;
});
b) add operation to operation queue
c) use an SyntaxChecker (which uses an NSTask) to do some other
processing of the File's content
4) When the SyntaxChecker's NSTask completes, it calls back to its delegate,
the MetaData collector, which then posts notification which is observed by a
view controller. I think this is all on the main thread. This view controller
is essentially the same as those I describe next, which handle displaying the
meta data that's gathered in the MetaDataOperation step.
5) When the MetaData collector gets the notification that an update has
completed, it then does some local state clean up and posts a notification
which is received by a number of view controllers, each of which controls the
display of different parts of the meta data. A typical handler in one of these
view controllers looks like this:
- (void) handleMetadataUpdate:(NSNotification*)aNote
{
[self performSelectorOnMainThread:@selector(updateUI) withObject:nil
waitUntilDone:NO];
}
In the updating of the UI, I do things like:
1) get the set of the relevant File entities from the view controller's
delegate
2) compare the meta data in the File entities to a local set of objects (which
hold references to their corresponding entities), and update any if necessary
3) reload outline view
Naturally, for the sake of brevity, I've simplified the picture a little, but
not much. I believe the salient points are described.
So, now my questions and issues:
1) How can I interpret the call graph shown below? I'm finding it difficult to
extract from that who's blocking whom.
2) Is there something glaringly wrong with the strategy I sketched above? (I
guess so, since it took a lot of experimentation to get it working at all.)
Many thanks for any clues, insights or advice anyone can offer,
Martin
-----------------------------------------------------
Call graph:
2771 Thread_4677360 DispatchQueue_1: com.apple.main-thread (serial)
+ 2771 start (in TeXnicle) + 52 [0x1000018e4]
+ 2771 main (in TeXnicle) + 34 [0x100001912] main.m:32
+ 2771 NSApplicationMain (in AppKit) + 869 [0x7fff829dfcb6]
+ 2771 -[NSApplication run] (in AppKit) + 517 [0x7fff82a3b283]
+ 2771 -[NSApplication
nextEventMatchingMask:untilDate:inMode:dequeue:] (in AppKit) + 128
[0x7fff82a43ed2]
+ 2771 _DPSNextEvent (in AppKit) + 685 [0x7fff82a44613]
+ 2771 BlockUntilNextEventMatchingListInMode (in HIToolbox) +
62 [0x7fff8a0e5cd3]
+ 2771 ReceiveNextEventCommon (in HIToolbox) + 356
[0x7fff8a0e5e42]
+ 2771 RunCurrentEventLoopInMode (in HIToolbox) + 209
[0x7fff8a0e60a4]
+ 2771 CFRunLoopRunSpecific (in CoreFoundation) + 290
[0x7fff81aaa6b2]
+ 2771 __CFRunLoopRun (in CoreFoundation) + 789
[0x7fff81aaadc5]
+ 2771 __CFRunLoopDoSources0 (in CoreFoundation) +
445 [0x7fff81a87aed]
+ 2771
__CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ (in CoreFoundation)
+ 17 [0x7fff81a88101]
+ 2771 _performFileHandleSource (in Foundation)
+ 1280 [0x7fff8a6dba7c]
+ 2771 -[NSNotificationCenter
postNotificationName:object:userInfo:] (in Foundation) + 64 [0x7fff8a61d846]
+ 2771 _CFXNotificationPost (in
CoreFoundation) + 2554 [0x7fff81abb47a]
+ 2771 -[TPSyntaxChecker
texOutputAvailable:] (in TeXnicle) + 535 [0x10017daa7] TPSyntaxChecker.m:481
+ 2771 -[TPSyntaxChecker
syntaxCheckerCheckDidFinish:] (in TeXnicle) + 258 [0x10017e282]
TPSyntaxChecker.m:518
+ 2771 -[TPFileEntityMetadata
syntaxCheckerCheckDidFinish:] (in TeXnicle) + 671 [0x1001975af]
TPFileEntityMetadata.m:249
+ 2771 -[TPFileEntityMetadata
postWarningsUpdateNotification] (in TeXnicle) + 107 [0x1001971ab]
TPFileEntityMetadata.m:225
+ 2771 -[NSNotificationCenter
postNotificationName:object:userInfo:] (in Foundation) + 64 [0x7fff8a61d846]
+ 2771 _CFXNotificationPost (in
CoreFoundation) + 2554 [0x7fff81abb47a]
+ 2771
-[TPWarningsViewController handleMetadataUpdate:] (in TeXnicle) + 70
[0x1001ab046] TPWarningsViewController.m:91
+ 2771
-[NSObject(NSThreadPerformAdditions)
performSelectorOnMainThread:withObject:waitUntilDone:] (in Foundation) + 131
[0x7fff8a6610c8]
+ 2771
-[NSObject(NSThreadPerformAdditions)
performSelector:onThread:withObject:waitUntilDone:modes:] (in Foundation) +
212 [0x7fff8a661220]
+ 2771
-[TPWarningsViewController updateUI] (in TeXnicle) + 56 [0x1001ac408]
TPWarningsViewController.m:235
+ 2771
-[TPWarningsViewController warningsViewlistOfFiles:] (in TeXnicle) + 258
[0x1001acf12] TPWarningsViewController.m:297
+ 2771
-[TeXProjectDocument warningsViewlistOfFiles:] (in TeXnicle) + 155
[0x100022cdb] TeXProjectDocument.m:4060
+ 2771
-[ProjectEntity items] (in TeXnicle) + 311 [0x1000288b7] ProjectEntity.m:94
+ 2771
-[NSManagedObjectContext executeFetchRequest:error:] (in CoreData) + 537
[0x7fff8bcae309]
+ 2771
-[NSPersistentStoreCoordinator executeRequest:withContext:error:] (in
CoreData) + 1138 [0x7fff8bcafba2]
+ 2771
-[_PFLock lock] (in CoreData) + 24 [0x7fff8bc9d548]
+ 2771
pthread_mutex_lock (in libsystem_c.dylib) + 536 [0x7fff824aad9d]
+ 2771
__psynch_mutexwait (in libsystem_kernel.dylib) + 10 [0x7fff8d1f0122]
2771 Thread_4677447 DispatchQueue_2: com.apple.libdispatch-manager
(serial)
+ 2771 _dispatch_mgr_thread (in libdispatch.dylib) + 54 [0x7fff8031c9ee]
+ 2771 _dispatch_mgr_invoke (in libdispatch.dylib) + 883
[0x7fff8031cdea]
+ 2771 kevent (in libsystem_kernel.dylib) + 10 [0x7fff8d1f0d16]
2771 Thread_4677448 DispatchQueue_129: NSOperation low-priority
concurrency-limiting queue (concurrent)
+ 2771 start_wqthread (in libsystem_c.dylib) + 13 [0x7fff82492171]
+ 2771 _pthread_wqthread (in libsystem_c.dylib) + 404 [0x7fff824a7cab]
+ 2771 _dispatch_worker_thread2 (in libdispatch.dylib) + 304
[0x7fff8031b1fa]
+ 2771 _dispatch_client_callout (in libdispatch.dylib) + 8
[0x7fff8031a0b6]
+ 2771 _dispatch_async_f_redirect_invoke (in libdispatch.dylib) +
117 [0x7fff8031f317]
+ 2771 _dispatch_client_callout (in libdispatch.dylib) + 8
[0x7fff8031a0b6]
+ 2771 _dispatch_call_block_and_release (in libdispatch.dylib)
+ 15 [0x7fff8031df01]
+ 2771 __103+[__NSOperationInternal
_observeValueForKeyPath:ofObject:changeKind:oldValue:newValue:indexes:context:]_block_invoke_0121
(in Foundation) + 49 [0x7fff8a719700]
+ 2771 __38-[TPFileEntityMetadata
updateMetadata]_block_invoke_0 (in TeXnicle) + 92 [0x100196dac]
TPFileEntityMetadata.m:168
+ 2771 _dispatch_barrier_sync_f_slow (in
libdispatch.dylib) + 188 [0x7fff8031ea92]
+ 2771 _dispatch_thread_semaphore_wait (in
libdispatch.dylib) + 16 [0x7fff8031ec32]
+ 2771 semaphore_wait_trap (in
libsystem_kernel.dylib) + 10 [0x7fff8d1ee6c2]
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