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If you are working on a native function or method, please take a moment to determine which of the following behaviors describe it:

1) Only called on AppKit thread

Use AWT_ASSERT_APPKIT_THREAD; (defined in ThreadUtilities.h)

2) Only NOT called on AppKit thread

Use AWT_ASSERT_NOT_APPKIT_THREAD; (defined in ThreadUtilities.h)

3) Called on any thread

Make sure any shared data (instance variables or global data) is accessed only as an atomic property, or behind a lock that will not block for an indefinite period of time.

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/System/Library/Frameworks/JavaVM.framework/Frameworks/JavaNativeFoundation.framework/Headers/JNFRunLoop.h

Native locks are evil

• Using pthread_lock() or NSLock will almost always get you in trouble
  • These locks are not recursive like Java locks are
• Using @synchronized in ObjC is slow
  • Since the lock storage is not in the object header itself (like it is in Java) a side-table must be consulted
• If you need to serialize execution of a task in native, use a serial GCD dispatch_queue
  • They are quite cheap to use in the uncontended case
• Avoid doing any work that will call back up into Java while holding a native lock or performing on a serial queue
  • It is very easy to deadlock with a Java semaphore and not realize it
    • These deadlocks are almost impossible to debug