Re: Handling Unix signals in a GTK+ application

[Tristan Van Berkom <tristan van berkom gmail com>]

David Necas (Yeti) wrote:

> On Thu, Mar 16, 2006 at 03:55:50PM -0500, Tristan Van Berkom wrote:
>  
>
> > Well, it locks a mutex before accessing the GMainContext; so if gtk+ is
> > compiled with threads... it should work... unless I'm on crack and mutexes
> > are useless from signal handlers... but I dont think so.
> >    
>
> Maybe I'm missing something, but how does this help when the
> signal is delivered to the thread which is just inside
> g_idle_add() (the only thread in a single-threaded program)?
>
>  
You are absolutely right; mutexes /are/ useless from signal handlers,
cooking the inline crack included below with gcc will prove it ;-)

It seems the only reasonable way is to use a pipe().

Cheers,
                        -Tristan

=======================================
#include <glib.h>
#include <signal.h>

GMutex *common_mutex;

void my_sigint (gint signum);

void
my_sigint (gint signum)
{
 signal (SIGINT, my_sigint);

 g_print ("Before lock\n");
 g_mutex_lock (common_mutex);
 g_print ("After lock\n");
}

gboolean
my_timeout (gpointer data)
{
 g_print ("Called\n");

 return TRUE;
}

void main()
{
 GMainLoop *loop;

 g_thread_init (NULL);
 if (!g_thread_supported ())
   g_error ("No thread support");


 signal (SIGINT, my_sigint);
 g_timeout_add (1000, my_timeout, NULL);

 loop = g_main_loop_new (NULL, FALSE);
 common_mutex = g_mutex_new ();

 g_mutex_lock (common_mutex);
 g_main_loop_run (loop);
}