subprocs.c

/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 8 -*-
 *
 * subprocs.c --- choosing, spawning, and killing screenhacks.
 *
 * xscreensaver, Copyright (c) 1991-2003 Jamie Zawinski <jwz@jwz.org>
 * Modified:     Copyright (c) 2004 William Jon McCann <mccann@jhu.edu>
 *
 * Permission to use, copy, modify, distribute, and sell this software and its
 * documentation for any purpose is hereby granted without fee, provided that
 * the above copyright notice appear in all copies and that both that
 * copyright notice and this permission notice appear in supporting
 * documentation.  No representations are made about the suitability of this
 * software for any purpose.  It is provided "as is" without express or
 * implied warranty.
 */

#include "config.h"

#include <stdlib.h>
#include <ctype.h>
#include <stdio.h>
#include <string.h>

#ifndef ESRCH
# include <errno.h>
#endif

#include <sys/time.h>		/* sys/resource.h needs this for timeval */
# include <sys/wait.h>		/* for waitpid() and associated macros */

#ifdef VMS
# include <processes.h>
# include <unixio.h>		/* for close */
# include <unixlib.h>		/* for getpid */
# define pid_t int
# define fork  vfork
#endif /* VMS */

#ifndef _POSIX_SOURCE
# define _POSIX_SOURCE
#endif
#include <signal.h>		/* for the signal names */

#include <glib.h>
#include "subprocs.h"

#if !defined(SIGCHLD) && defined(SIGCLD)
# define SIGCHLD SIGCLD
#endif

/* Semaphore to temporarily turn the SIGCHLD handler into a no-op.
   Don't alter this directly -- use block_sigchld() / unblock_sigchld().
*/
static int block_sigchld_handler = 0;


sigset_t
block_sigchld (void)
{
	sigset_t child_set;
	sigemptyset (&child_set);
	sigaddset (&child_set, SIGCHLD);
	sigaddset (&child_set, SIGPIPE);
	sigprocmask (SIG_BLOCK, &child_set, 0);
	block_sigchld_handler++;
	return child_set;
}

void
unblock_sigchld (void)
{
	sigset_t child_set;
	sigemptyset (&child_set);
	sigaddset (&child_set, SIGCHLD);
	sigaddset (&child_set, SIGPIPE);
	sigprocmask (SIG_UNBLOCK, &child_set, 0);
	block_sigchld_handler--;
}

int
signal_pid (int    pid,
	    int    signal)
{
	int status = -1;
	gboolean verbose = TRUE;

	if (block_sigchld_handler)
		/* This function should not be called from the signal handler. */
		abort();

	block_sigchld ();                      /* we control the horizontal... */

	status = kill (pid, signal);

	if (verbose && status < 0) {
		if (errno == ESRCH)
			g_message ("Child process %lu was already dead.",
				   (unsigned long) pid);
		else {
			char buf [1024];
			snprintf (buf, sizeof (buf), "Couldn't kill child process %lu",
				 (unsigned long) pid);
			perror (buf);
		}
	}

	unblock_sigchld ();

	if (block_sigchld_handler < 0)
		abort ();

	return status;
}

#ifndef VMS

void
await_dying_children (int      pid,
		      gboolean debug)
{
	while (1) {
		int wait_status = 0;
		pid_t kid;

		errno = 0;
		kid = waitpid (-1, &wait_status, WNOHANG|WUNTRACED);

		if (debug) {
			if (kid < 0 && errno)
				g_message ("waitpid(%d) ==> %ld (%d)", pid, (long) kid, errno);
			else if (kid != 0)
				g_message ("waitpid(%d) ==> %ld", pid, (long) kid);
		}

		/* 0 means no more children to reap.
		   -1 means error -- except "interrupted system call" isn't a "real"
		   error, so if we get that, we should just try again. */
		if (kid < 0 && errno != EINTR)
			break;
	}
}


#else  /* VMS */
static void await_dying_children (saver_info *si) { return; }
#endif /* VMS */