From 64fa37f09b29a7675246a36361e25fd218ab7852 Mon Sep 17 00:00:00 2001
From: Jaroslav Kysela <perex@perex.cz>
Date: Tue, 1 Feb 2022 20:45:27 +0100
Subject: alsactl: lock - use alarm signal and F_SETLKW rather polling

Signed-off-by: Jaroslav Kysela <perex@perex.cz>
---
 alsactl/lock.c | 41 ++++++++++++++++++++++++++++++++++-------
 1 file changed, 34 insertions(+), 7 deletions(-)

(limited to 'alsactl')

diff --git a/alsactl/lock.c b/alsactl/lock.c
index aa77254..0238e95 100644
--- a/alsactl/lock.c
+++ b/alsactl/lock.c
@@ -27,15 +27,26 @@
 #include <fcntl.h>
 #include <errno.h>
 #include <string.h>
+#include <signal.h>
+#include <sys/time.h>
 #include <sys/stat.h>
 #include "alsactl.h"
 
+static int alarm_flag;
+
+static void signal_handler_alarm(int sig)
+{
+	alarm_flag = 1;
+}
+
 static int state_lock_(int lock, int timeout, int _fd)
 {
 	int fd = -1, err = 0;
 	struct flock lck;
 	struct stat st;
 	char lcktxt[14];
+	struct sigaction sig_alarm, sig_alarm_orig;
+	struct itimerval itv;
 	char *nfile = lockfile;
 
 	if (do_lock <= 0)
@@ -93,15 +104,31 @@ static int state_lock_(int lock, int timeout, int _fd)
 			goto out;
 		}
 	}
-	while (timeout > 0) {
-		if (fcntl(fd, F_SETLK, &lck) < 0) {
-			sleep(1);
-			timeout--;
-		} else {
+	alarm_flag = 0;
+	memset(&sig_alarm, 0, sizeof(sig_alarm));
+	sigemptyset(&sig_alarm.sa_mask);
+	sig_alarm.sa_handler = signal_handler_alarm;
+	if (sigaction(SIGALRM, &sig_alarm, &sig_alarm_orig) < 0) {
+		err = -ENXIO;
+		goto out;
+	}
+	memset(&itv, 0, sizeof(itv));
+	itv.it_value.tv_sec = timeout;
+	if (setitimer(ITIMER_REAL, &itv, NULL) < 0) {
+		err = -ENXIO;
+		sigaction(SIGALRM, &sig_alarm_orig, NULL);
+		goto out;
+	}
+	while (alarm_flag == 0) {
+		if (fcntl(fd, F_SETLKW, &lck) == 0)
 			break;
-		}
+		if (errno == EAGAIN || errno == ERESTART)
+			continue;
 	}
-	if (timeout <= 0) {
+	memset(&itv, 0, sizeof(itv));
+	setitimer(ITIMER_REAL, &itv, NULL);
+	sigaction(SIGALRM, &sig_alarm_orig, NULL);
+	if (alarm_flag) {
 		err = -EBUSY;
 		goto out;
 	}
-- 
cgit v1.2.1