alsa-utils/0007-aplay-fix-the-CPU-busy-loop-in-the-pause-handler.patch

From c1b92db5ef01311e5fc983f3134caa00826d0c2d Mon Sep 17 00:00:00 2001
From: Jaroslav Kysela <perex@perex.cz>
Date: Sun, 8 Nov 2020 19:11:12 +0100
Subject: [PATCH 07/25] 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>
---
 aplay/aplay.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/aplay/aplay.c b/aplay/aplay.c
index ae609880bfd7..d385da25fea1 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);
 			}
-- 
2.26.2