[Libevent-users] Bug in signal.c

[Scott Lamb]

On May 28, 2007, at 8:28 AM, Jesse Keller wrote:

> Just implemented libevent in a new program using the cool eventxx C++
> wrapper.  Anyway, I decided to track down the event_base_free bug a
> little more.  Here's the original bug and patch.
>
> http://monkeymail.org/archives/libevent-users/2006-April/000141.html
>
> Seems that we don't need to go through all that effort of fixing the
> symptom, it's just that the internal event between the signal handler
> and the dispatcher is never deleted.
>
> Here's the patch that fixes the problem for me (versus the 1.3b  
> release)
>
>
> --- signal.c    2007-03-03 23:05:07.000000000 -0500
> +++ signal.c.new        2007-05-28 11:10:57.000000000 -0400
> @@ -143,6 +143,11 @@
>         int evsignal;
>
>         evsignal = EVENT_SIGNAL(ev);
> +
> +       if (ev_signal_added) {
> +               ev_signal_added = 0;
> +               event_del(&ev_signal);
> +       }
>
>         return (sigaction(EVENT_SIGNAL(ev),(struct sigaction *) 
> SIG_DFL,
> NULL));
>  }

But ev_signal is for the pipe used to wake up on receipt of *any*  
signal. Consider this code snippet:

     signal_set(&ev1, SIGUSR1, signal_cb, NULL);
     event_add(&ev1, NULL);
     signal_set(&ev2, SIGUSR2, signal_cb, NULL);
     event_add(&ev2, NULL);
     event_del(&ev2);

     raise(SIGUSR1);
     event_dispatch(EVLOOP_ONCE);

without your change, the dispatch would return immediately. With your  
change, it would wait until timeout.

-- 
Scott Lamb <http://www.slamb.org/>