As the last preparations for the MacOS X final release take place the one or other show stopper bug pops up. One particular nasty one was in reality rearing its ugly head in July for the first time. The problem is that if an app does pretty heavily use setitimer sometimes SIGALRM get lost. If the app is waiting on some timed event the app will stall and if a kill with SIGALRM is used from the command line the app will continue. The very same problem did appear years ago on SunOS 4.1.3 and was fixed by Sun with a patch. Unfortunately SunOS is closed source and thus I do not know exactly what the fix was, but looking through the FreeBSD cvs I believe that I may have found the culprit. There appears to be rare case that the setitimer mechanism might inccur a race condition with the hardware tick timer, the fix was at 1.9 of kern_time.c.