Re: Run loops
Re: Run loops
- Subject: Re: Run loops
- From: Mike Laster <email@hidden>
- Date: Fri, 05 Jul 2002 21:28:54 -0400
On 7/5/02 8:44 PM, "Douglas Davidson" <email@hidden> wrote:
>
On Wednesday, July 3, 2002, at 02:41 PM, Mike Laster wrote:
>
>
> How do I externally force a run loop to "wake up"?
>
>
>
> What I'm trying to do is have my server gracefully shutdown after
>
> receiving
>
> a SIGINT.
>
>
Very few calls are async-signal-safe. I am told that send() and
>
mach_msg() are among them. So, one approach would be to set up an
>
appropriate run loop source (CFSocket, for a socket, or CFMachPort, for
>
a Mach port) and message the underlying socket or Mach port from your
>
signal handler. The Mach port approach probably has lower overhead,
>
but you may be more familiar with the socket approach; socketpair() is
>
useful for this sort of thing.
I ended up hacking together a "version 0" runloop source that uses a
dedicated thread to watch for the event, and a sig handler of:
void _signalHandler(int sig)
{
pthread_mutex_lock(&_signalMutex);
_pendingSignal = sig;
pthread_mutex_unlock(&_signalMutex);
pthread_cond_broadcast(&_signalCondition);
}
Which wakes the thread up, which in turn signals the run loop source.
This seems to work, but I don't like having that extra thread lying around.
I'm also not 100% sure pthread_* calls are async safe, though it seems to
work consistently.
I'd like to convert to a "type 1" approach, but am not sure about mach
messaging. I know I can't use NSMachPort since I can't reliablly use ObjC
from inside of a signal handler.
If I do the Mach port approach, can I do it without the extra thread? I'm
not sure if a thread cand send a message "to itself" so to speak. Where it
sends a message in the handler, and then receives it in the run loop.
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| References: | |
| | >Re: Run loops (From: Douglas Davidson <email@hidden>) |