openrc-shutdown: broadcast: simplify non-blocking logic

The sigsetjump/siglongjmp logic originates from sysvinit, and was added before the fork() call was there. Instead of playing games with signal handlers, just let the kernel kill the process with SIGALARM if write() blocks for some unknown reason. Bug: https://bugs.gentoo.org/923326 Signed-off-by: Mike Gilbert <[email protected]>
OpenRC · May 23, 2024 · 9236460 · 9236460
1 parent 3d30b6f
commit 9236460
Showing 1 changed file with 13 additions and 40 deletions.
diff --git a/src/openrc-shutdown/broadcast.c b/src/openrc-shutdown/broadcast.c
@@ -17,8 +17,6 @@
 #include <fcntl.h>
 #include <paths.h>
 #include <pwd.h>
-#include <signal.h>
-#include <setjmp.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -37,15 +35,6 @@
 # define _PATH_DEV	"/dev/"
 #endif
 
-static sigjmp_buf jbuf;
-
-/*
- *	Alarm handler
- */
-RC_NORETURN static void handler(int arg RC_UNUSED)
-{
-	siglongjmp(jbuf, 1);
-}
 
 static void getuidtty(char **userp, char **ttyp)
 {
@@ -123,16 +112,11 @@ void broadcast(char *text)
 	char	*date;
 	char *p;
 	char *line = NULL;
-	struct sigaction sa;
 	int	flags;
 	char *term = NULL;
 	struct utmpx *utmp;
-	/*
-	 * These are set across the sigsetjmp call, so they can't be stored on
-	 * the stack, otherwise they might be clobbered.
-	 */
-	static int fd;
-	static FILE *tp;
+	int fd;
+	FILE *tp;
 
 	getuidtty(&user, &tty);
 
@@ -159,11 +143,6 @@ void broadcast(char *text)
 	if (fork() != 0)
 		return;
 
-	memset(&sa, 0, sizeof(sa));
-	sa.sa_handler = handler;
-	sigemptyset(&sa.sa_mask);
-	sigaction(SIGALRM, &sa, NULL);
-
 	setutxent();
 
 	while ((utmp = getutxent()) != NULL) {
@@ -178,25 +157,19 @@ void broadcast(char *text)
 			continue;
 		}
 
-		/*
-		 *	Open it non-delay
-		 */
-		if (sigsetjmp(jbuf, 1) == 0) {
-			alarm(2);
-			flags = O_WRONLY|O_NDELAY|O_NOCTTY;
-			if (file_isatty(term) && (fd = open(term, flags)) >= 0) {
-				if (isatty(fd) && (tp = fdopen(fd, "w")) != NULL) {
-					fputs(line, tp);
-					fputs(text, tp);
-					fflush(tp);
-				}
+		/* Request non-blocking I/O */
+		flags = O_WRONLY|O_NONBLOCK|O_NOCTTY;
+		if (file_isatty(term) && (fd = open(term, flags)) >= 0) {
+			if (isatty(fd) && (tp = fdopen(fd, "w")) != NULL) {
+				alarm(2); /* Let the kernel kill us if write() blocks */
+				fputs(line, tp);
+				fputs(text, tp);
+				fclose(tp);
+				alarm(0);
 			}
+			else
+				close(fd);
 		}
-		alarm(0);
-		if (fd >= 0)
-			close(fd);
-		if (tp != NULL)
-			fclose(tp);
 		free(term);
 	}
 	endutxent();