On Feb 21, 2012, at 6:50 AM, Dragan Milić <mi...@mac.com> wrote: > First of all, I apologise if this is not the right topic for this list. > > Some beta testers of an application I'm working on experience rather strange > and sudden crashes, very often when the application is doing nothing, just > sitting idle in the background. The crash happens in a thread named > "com.apple.root.default-priority" and it's not even controlled by the > application. As far as I figure it out, it is triggered by the system to > release some memory from caches the application uses. This is the part of the > crash report related to that particular thread: > > Thread 8 Crashed:: Dispatch queue: com.apple.root.default-priority > 0 libsystem_kernel.dylib 0x00007fff8d847ce2 __pthread_kill + 10 > 1 libsystem_c.dylib 0x00007fff9009e7d2 pthread_kill + 95 > 2 libsystem_c.dylib 0x00007fff9008fa7a abort + 143 > 3 libc++abi.dylib 0x00007fff8a1e77bc abort_message + 214 > 4 libc++abi.dylib 0x00007fff8a1e4fcf default_terminate() > + 28 > 5 libobjc.A.dylib 0x00007fff8a69a1b9 _objc_terminate + 94 > 6 libc++abi.dylib 0x00007fff8a1e5001 > safe_handler_caller(void (*)()) + 11 > 7 libc++abi.dylib 0x00007fff8a1e505c std::terminate() + 16 > 8 libc++abi.dylib 0x00007fff8a1e6152 __cxa_throw + 114 > 9 libobjc.A.dylib 0x00007fff8a699e7a objc_exception_throw > + 327 > 10 com.apple.CoreFoundation 0x00007fff8c8b92a9 -[NSException raise] > + 9 > 11 com.apple.ExceptionHandling 0x0000000100332e0a > NSExceptionHandlerUncaughtSignalHandler + 37 > 12 libsystem_c.dylib 0x00007fff900f0cfa _sigtramp + 26 > 13 com.apple.CoreFoundation 0x00007fff8c793c0b CFRelease + 27 > 14 libcache.dylib 0x00007fff8fb4d8e4 _value_entry_remove > + 142 > 15 libcache.dylib 0x00007fff8fb4d9cd _entry_unmap + 81 > 16 libcache.dylib 0x00007fff8fb4da71 _entry_evict + 153 > 17 libcache.dylib 0x00007fff8fb4db04 _evict_last + 106 > 18 libcache.dylib 0x00007fff8fb4dcf2 > _cache_enforce_limits + 34 > 19 libcache.dylib 0x00007fff8fb4dea5 > cache_handle_memory_pressure + 125 > 20 libdispatch.dylib 0x00007fff888bf2b6 > _dispatch_source_invoke + 635 > 21 libdispatch.dylib 0x00007fff888bbf77 > _dispatch_queue_invoke + 71 > 22 libdispatch.dylib 0x00007fff888bb760 > _dispatch_worker_thread2 + 198 > 23 libsystem_c.dylib 0x00007fff9009e3da _pthread_wqthread + > 316 > 24 libsystem_c.dylib 0x00007fff9009fb85 start_wqthread + 13 > > All those crash reports for the crashing thread look the same. Only a few > people experience them, but regularly. For others, it practically impossible > to reproduce. > > I'm using higher level Cocoa NSCache API to cache objects. Cached objects are > various image representations and much rarely attributed strings and NSNumber > instances. I see the crash happens after CFRelease() call, but I can't figure > out why. If I try to do CFRelease(NULL), I get almost the same sequence, > similar to: > > 3 libc++abi.dylib 0x00007fff8a1e77bc abort_message + 214 > 4 libc++abi.dylib 0x00007fff8a1e4fcf default_terminate() > + 28 > 5 libobjc.A.dylib 0x00007fff8a69a1b9 _objc_terminate + 94 > 6 libc++abi.dylib 0x00007fff8a1e5001 > safe_handler_caller(void (*)()) + 11 > 7 libc++abi.dylib 0x00007fff8a1e505c std::terminate() + 16 > 8 libc++abi.dylib 0x00007fff8a1e6152 __cxa_throw + 114 > 9 libobjc.A.dylib 0x00007fff8a699e7a objc_exception_throw > + 327 > 10 com.apple.CoreFoundation 0x00007fff8c8b92a9 -[NSException raise] > + 9 > 11 com.apple.ExceptionHandling 0x0000000100332e0a > NSExceptionHandlerUncaughtSignalHandler + 37 > 12 libsystem_c.dylib 0x00007fff900f0cfa _sigtramp + 26 > > But I don't know who and why does (if at all) that NULL pointer release. The > documentation for libcache says "Calling cache functions from cache callbacks > should be avoided to prevent deadlock." I thought maybe when releasing cached > objects libcache calls callback methods to release memory and then image > representations are doing some caching on their own, which would effectively > be calling cache functions from cache callbacks. But this is just a wild > guess, I've no idea what is really going on. > > So, I'd really appreciate if anyone can help me with this. I've got no idea > whether it's a but in the application, or the OS. If necessary, I can send > the full crash report and also explain what object are being cached using > NSCache.
Yep, that's CFRelease(NULL), plus ExceptionHandling.framework catching the Unix signal and trying to turn it into an Objective-C exception. That background thread is part of NSCache. This could be a bug in your use of NSCache, a memory smasher somewhere, or a bug in NSCache itself. You may be able to reproduce this by forcing the app into a low memory situation. That background thread is evicting NSCache contents in responds to low memory. Once you can reproduce, you should try zombies and guard malloc. -- Greg Parker gpar...@apple.com Runtime Wrangler _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
