From: Jaroslav Kysela <perex@perex.cz>
Date: Sun, 8 Nov 2020 18:11:12 +0000 (+0100)
Subject: aplay: fix the CPU busy loop in the pause handler
X-Git-Tag: v1.2.5~103
X-Git-Url: https://git.alsa-project.org/?a=commitdiff_plain;h=c1b92db5ef01311e5fc983f3134caa00826d0c2d;p=alsa-utils.git

aplay: fix the CPU busy loop in the pause handler

Use the standard poll mechanism to ensure that there's
something in the input to avoid busy loop on the file
descriptor with the non-block mode set.

Signed-off-by: Jaroslav Kysela <perex@perex.cz>
---

diff --git a/aplay/aplay.c b/aplay/aplay.c
index ae60988..d385da2 100644
--- a/aplay/aplay.c
+++ b/aplay/aplay.c
@@ -1553,6 +1553,19 @@ static void done_stdin(void)
 	tcsetattr(fileno(stdin), TCSANOW, &term);
 }
 
+static char wait_for_input(void)
+{
+	struct pollfd pfd;
+	unsigned char b;
+
+	do {
+		pfd.fd = fileno(stdin);
+		pfd.events = POLLIN;
+		poll(&pfd, 1, -1);
+	} while (read(fileno(stdin), &b, 1) != 1);
+	return b;
+}
+
 static void do_pause(void)
 {
 	int err;
@@ -1571,7 +1584,7 @@ static void do_pause(void)
 		return;
 	}
 	while (1) {
-		while (read(fileno(stdin), &b, 1) != 1);
+		b = wait_for_input();
 		if (b == ' ' || b == '\r') {
 			while (read(fileno(stdin), &b, 1) == 1);
 			if (snd_pcm_state(handle) == SND_PCM_STATE_SUSPENDED)
@@ -1596,7 +1609,7 @@ static void check_stdin(void)
 				while (read(fileno(stdin), &b, 1) == 1);
 				fprintf(stderr, _("\r=== PAUSE ===                                                            "));
 				fflush(stderr);
-			do_pause();
+				do_pause();
 				fprintf(stderr, "                                                                          \r");
 				fflush(stderr);
 			}