On Apr 8, 2010, at 10:40 PM, vincent habchi wrote:
>> void CFRunLoopWakeUp(CFRunLoopRef rl) {
>> CHECK_FOR_FORK();
>> #if DEPLOYMENT_TARGET_MACOSX || DEPLOYMENT_TARGET_EMBEDDED
>> kern_return_t ret;
>> /* We unconditionally try to send the message, since we don't want
>> * to lose a wakeup, but the send may fail if there is already a
>> * wakeup pending, since the queue length is 1. */
>> ret = __CFSendTrivialMachMessage(rl->_wakeUpPort, 0, MACH_SEND_TIMEOUT,
>> 0);
>> if (ret != MACH_MSG_SUCCESS && ret != MACH_SEND_TIMED_OUT) {
>> HALT;
>> }
>
> Okay, so that means it is impossible to ask a run loop to stop while it is
> being messaged to wake up. Practically, this might not be a severe threat,
> but when you begin to create/destroy threads at small intervals (say, 50 ms),
> the collision seems to be inevitable (especially since I also use timers to
> wake up the loops). I wonder why the queue has only a single entry.
In this circumstance, mach_msg() will block if the queue is full, and either
succeed later or time out. Neither of those paths should end up at HALT.
(mach_msg() may do other things in other circumstances.)
Presumably mach_msg() returned something other than MACH_MSG_SUCCESS or
MACH_SEND_TIMED_OUT in your example. What's in register rax in your crash log?
--
Greg Parker gpar...@apple.com Runtime Wrangler
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