Re: Race condition in list_consume()

Wow. This was exactly the kind of thing I was hunting for ages...
So a simple         warning(0, "SIGHUP received, catching and re- 
opening logs");
was killing it...
Thanks a lot...


On 17.04.2007, at 14:20, Raul Igrisan wrote:

> I was not able to reproduce the hang by running the code you’ve  
> mentioned UNTIL I hit it with
>
> for ((;1;)); do kill -s SIGHUP 12374; done;
>
> from another console.
>
>
>
> It hung and DDD clearly showed why:
>
> SIGHUP was delivered to the main thread(1) which became alertable  
> during executing warning(...), after it managed to add a producer  
> and hung trying to reacquire the permanent lock when called warning 
> (...) again.
>
> But the lock was held by ThreadC (3) waiting for the producer to be  
> removed.
>
>
>
> Now every thread calling debug/warning/ etc will hang.
>
>
>
> You may avoid this by not calling gwlib directly from the signal  
> handler (by setting a flag for example).
>
> The pthreads mutex functions are not async signal safe anyway and  
> are not to be called from signal handlers.
>
>
>
>
>
>
>
> From: Andreas Fink [mailto:[email protected]]
> Sent: 17 April 2007 03:26
> To: Raul Igrisan
> Cc: 'devel Devel'
> Subject: Re: Race condition in list_consume()
>
>
>
> I can now easily reproduce the problem with the attached code. It  
> will run for a few seconds and then deadlock.
>
>
>
> <ThreadC(3).JPG>
> <MainThread(1).JPG>



Andreas Fink

Fink Consulting GmbH
Global Networks Schweiz AG
BebbiCell AG

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