Take a step back, observe what the app does. Whether it blocks on slow system calls or coarse grained locks is irrelevant. The point is, the GUI thread hangs.

Take a step back, observe what the app does. Whether it blocks on slow system calls or coarse grained locks is irrelevant. The point is, the GUI thread hangs. That isn't supposed to happen. Quite a bit of Apple software does this. This suggests that this is somewhat systemic.