[asterisk-dev] SIGHUP handling

[Russell Bryant]

We have various bug reports that show crashes within malloc/calloc, so I 
started thinking about possible things that could happen to corrupt the 
internals of malloc.

One thing is the use of memory allocation functions within a signal 
handler.  I did an audit of the signal handlers in asterisk.c and there 
is one that does something very bad.

static void hup_handler(int num)
{
     if (option_verbose > 1)
         printf("Received HUP signal -- Reloading configs\n");
     if (restartnow)
         execvp(_argv[0], _argv);
     /* XXX This could deadlock XXX */
     ast_module_reload(NULL);
     signal(num, hup_handler);
}

One way SIGHUP is used is to trigger a restart of all of Asterisk if 
Asterisk is running with the -c option.  That's fine, because it will 
never go past execvp().  However, should SIGHUP be received for some 
other reason, calling ast_module_reload() is very bad if it interrupts a 
call to malloc/calloc/etc., or some other non-reentrant function that 
will then be called again during the reload process.

So, can anyone think of a good reason why this hander calls 
ast_module_reload()?

-- 
Russell Bryant
Software Engineer
Digium, Inc.