NSImage _cacheSnapShotRep crash

I'm creating images using an NSOperation subclass; threads are spawned to create the images which are displayed in an imageView. The images are set as a key in an arraycontroller, which is bound to the imageview.

Users are randomly reporting the app crashes and the crash log is showing an 开发者_运维技巧error in a thread calling the selector _cacheSnapshotRep(); I've been unable to reproduce this myself and there's nothing coming up in web searches for this error.

Here are the relevant sections from the crash log:

Exception Type:  EXC_BAD_ACCESS (SIGBUS)
Exception Codes: KERN_PROTECTION_FAILURE at 0x0000000000000000
Crashed Thread:  5  Dispatch queue: com.apple.root.default-priority

Application Specific Information:
objc_msgSend() selector name: _cacheSnapshotRep:

And:

Thread 5 Crashed:  Dispatch queue: com.apple.root.default-priority
0   libobjc.A.dylib                 0x90008edb objc_msgSend + 27
1   com.apple.AppKit                0x962abd48 -[NSImage _usingBestRepresentationForRect:context:hints:body:] + 189
2   com.apple.AppKit                0x962ab87e -[NSImage drawInRect:fromRect:operation:fraction:respectFlipped:hints:] + 1939
3   com.apple.AppKit                0x962aa6a0 -[NSImage _drawMappingAlignmentRectToRect:withState:backgroundStyle:operation:fraction:flip:hints:] + 842
4   com.apple.AppKit                0x963bfb95 -[NSImageCell drawInteriorWithFrame:inView:] + 821
5   com.apple.AppKit                0x963bf7f9 -[NSImageCell drawWithFrame:inView:] + 2133
6   com.apple.AppKit                0x9635066a -[NSControl drawRect:] + 589
7   com.apple.AppKit                0x96348a99 -[NSView _drawRect:clip:] + 3510
8   com.apple.AppKit                0x969ae107 -[_NSViewDrawOperation main] + 257
9   com.apple.Foundation            0x9279c33b -[__NSOperationInternal start] + 811
10  com.apple.Foundation            0x9279bf61 ____startOperations_block_invoke_2 + 94
11  libSystem.B.dylib               0x922ac828 _dispatch_call_block_and_release + 16
12  libSystem.B.dylib               0x9229ea5c _dispatch_worker_thread2 + 222
13  libSystem.B.dylib               0x9229e4f1 _pthread_wqthread + 390
14  libSystem.B.dylib               0x9229e336 start_wqthread + 30

I'm a bit lost as to where to go with this from here, so any advice is appreciated.

Exception Type:  EXC_BAD_ACCESS (SIGBUS)

Looks like a memory management issue to me, NSZombieEnabled or Instruments should aid you in finding what is wrong, especially if you can't reproduce the error yourself.

So it's looking like it's caused by using non-thread safe classes in my sub-threads.

Apple's documentation gives a nice summary of the thread safety rules.