linux-kernel - [PATCH v2] Documentation/watchdog: check return value for magic close

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Date:	Tue, 19 Jul 2016 17:41:22 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Wim Van Sebroeck <wim@...ana.be>
Cc:	Arnd Bergmann <arnd@...db.de>, Guenter Roeck <linux@...ck-us.net>,
	Jonathan Corbet <corbet@....net>,
	Timur Tabi <timur@...eaurora.org>,
	linux-watchdog@...r.kernel.org, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2] Documentation/watchdog: check return value for magic close

A recent commit added a write to the watchdog test code for doing the "magic
close", but that caused a compile-time warning:

Documentation/watchdog/src/watchdog-test.c: In function ‘main’:
Documentation/watchdog/src/watchdog-test.c:94:5: warning: ignoring return value of ‘write’, declared with attribute warn_unused_result [-Wunused-result]

This changes the code to print a runtime warning if the write fails.

Fixes: 5a2d3de19602 ("Documentation/watchdog: add support for magic close to watchdog-test")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
v2: fix typo as pointed out by both Guenter Roeck and Randy Dunlap
---
 Documentation/watchdog/src/watchdog-test.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/Documentation/watchdog/src/watchdog-test.c b/Documentation/watchdog/src/watchdog-test.c
index c69153913722..6983d05097e2 100644
--- a/Documentation/watchdog/src/watchdog-test.c
+++ b/Documentation/watchdog/src/watchdog-test.c
@@ -2,6 +2,7 @@
  * Watchdog Driver Test Program
  */
 
+#include <errno.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -35,9 +36,13 @@ static void keep_alive(void)
 
 static void term(int sig)
 {
-    write(fd, &v, 1);
+    int ret = write(fd, &v, 1);
+
     close(fd);
-    printf("\nStopping watchdog ticks...\n");
+    if (ret < 0)
+	printf("\nStopping watchdog ticks failed (%d)...\n", errno);
+    else
+	printf("\nStopping watchdog ticks...\n");
     exit(0);
 }
 
@@ -45,6 +50,7 @@ int main(int argc, char *argv[])
 {
     int flags;
     unsigned int ping_rate = 1;
+    int ret;
 
     setbuf(stdout, NULL);
 
@@ -91,7 +97,9 @@ int main(int argc, char *argv[])
 	sleep(ping_rate);
     }
 end:
-    write(fd, &v, 1);
+    ret = write(fd, &v, 1);
+    if (ret < 0)
+	printf("Stopping watchdog ticks failed (%d)...\n", errno);
     close(fd);
     return 0;
 }
-- 
2.9.0