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From: Peter Wemm <peter@FreeBSD.org>
To: Perforce Change Reviews <perforce@freebsd.org>
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Subject: PERFORCE change 204545 for review
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http://p4web.freebsd.org/@@204545?ac=10

Change 204545 by peter@peter_daintree on 2012/01/13 18:35:28

	vfork() is not deprecated and isn't going anywhere.  Revert the misguided
	part 4 of change 16117 back from 1996.  At work we see 1000x improvements
	in certain pathological workloads.

Affected files ...

.. //depot/projects/hammer/lib/libc/stdlib/system.c#4 edit

Differences ...

==== //depot/projects/hammer/lib/libc/stdlib/system.c#4 (text+ko) ====

@@ -56,39 +56,39 @@
 	if (!command)		/* just checking... */
 		return(1);
 
-	/*
-	 * Ignore SIGINT and SIGQUIT, block SIGCHLD. Remember to save
-	 * existing signal dispositions.
-	 */
-	ign.sa_handler = SIG_IGN;
-	(void)sigemptyset(&ign.sa_mask);
-	ign.sa_flags = 0;
-	(void)_sigaction(SIGINT, &ign, &intact);
-	(void)_sigaction(SIGQUIT, &ign, &quitact);
 	(void)sigemptyset(&newsigblock);
 	(void)sigaddset(&newsigblock, SIGCHLD);
 	(void)_sigprocmask(SIG_BLOCK, &newsigblock, &oldsigblock);
-	switch(pid = fork()) {
+	switch(pid = vfork()) {
 	case -1:			/* error */
 		break;
 	case 0:				/* child */
 		/*
 		 * Restore original signal dispositions and exec the command.
 		 */
-		(void)_sigaction(SIGINT, &intact, NULL);
-		(void)_sigaction(SIGQUIT,  &quitact, NULL);
 		(void)_sigprocmask(SIG_SETMASK, &oldsigblock, NULL);
 		execl(_PATH_BSHELL, "sh", "-c", command, (char *)NULL);
 		_exit(127);
 	default:			/* parent */
+		/* 
+		 * If we are running means that the child has either completed
+		 * its execve, or has failed.
+		 * Block SIGINT/QUIT because sh -c handles it and wait for
+		 * it to clean up.
+		 */
+		ign.sa_handler = SIG_IGN;
+		(void)sigemptyset(&ign.sa_mask);
+		ign.sa_flags = 0;
+		(void)_sigaction(SIGINT, &ign, &intact);
+		(void)_sigaction(SIGQUIT, &ign, &quitact);
 		savedpid = pid;
 		do {
 			pid = _wait4(savedpid, &pstat, 0, (struct rusage *)0);
 		} while (pid == -1 && errno == EINTR);
+		(void)_sigaction(SIGINT, &intact, NULL);
+		(void)_sigaction(SIGQUIT,  &quitact, NULL);
 		break;
 	}
-	(void)_sigaction(SIGINT, &intact, NULL);
-	(void)_sigaction(SIGQUIT,  &quitact, NULL);
 	(void)_sigprocmask(SIG_SETMASK, &oldsigblock, NULL);
 	return(pid == -1 ? -1 : pstat);
 }