Subj : NPTL and sigwait() problem under linux
To   : comp.programming.threads
From : Daniele
Date : Tue Aug 16 2005 07:18 pm

I want to create a thread that handles all the signals sent to the 
process, and all the other threads shouldn't be aware of signals at all.

I used sigprocmask() to block all the signals before creating any 
thread, then I spawn a thread that calls sigwait(), and it used to work 
(with LinuxThreads). Now I have a debian sid system, with kernel 
2.6.11.7 and NPTL, and it doesn't work anymore.
I tried to use pthread_sigmask instead of sigprocmask(), but nope.

Thanks for any help,
Daniele


This is the code:

static int terminate = 0;
void* signal_thread(void* param)
{
     sigset_t *set = (sigset_t*) param;
     int sig;
     while(!terminate) {
         sigwait(set, &sig);
         switch(sig) {
         case SIGINT:
         case SIGTERM:
	    /* ...do cleanup, etc... */
             terminate = 1;
             break;
         case SIGUSR1:
	    /* ...handle the signal here...  */
	    break;
     }
     return NULL;
}

static pthread_t sig_thr = (pthread_t) 0;
void signal_init(void)
{
     static sigset_t signals;
     int err;
     sigemptyset(&signals);
     sigaddset(&signals, SIGTERM);
     sigaddset(&signals, SIGINT);
     sigaddset(&signals, SIGUSR1);
     sigprocmask(SIG_BLOCK, &signals, NULL);
     err = pthread_create(&sig_thr, NULL, signal_thread, &signals);
     if(err != 0) {
         fprintf(stderr, "signal_init (pthread_create): %s\n", 
strerror(err));
         exit(err);
     }
}

void signal_finish(void)
{
     if(sig_thr != (pthread_t) 0) {
         pthread_cancel(sig_thr);
         pthread_join(sig_thr, NULL);
     }
}

int main(void)
{
     signal_init();
     /* ... run program, create other threads, etc... */
     signal_finish();
     return 0;
}

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