linux-kernel - [PATCH v2 2/2] watchdog: dw_wdt: keepalive the watchdog at write time

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Date:	Thu,  7 May 2015 21:27:45 -0700
From:	Doug Anderson <dianders@...omium.org>
To:	wim@...ana.be, linux@...ck-us.net
Cc:	jszhang@...vell.com, Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Doug Anderson <dianders@...omium.org>,
	linux-watchdog@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2 2/2] watchdog: dw_wdt: keepalive the watchdog at write time

If you've got code that does this in a tight loop
  1. Open watchdog
  2. Send 'expect close'
  3. Close watchdog
...you'll eventually trigger a watchdog reset.  You can reproduce this
by using daisydog (1) and running:
  while true; do daisydog -c > /dev/null; done

The problem is that each time you write to the watchdog for 'expect
close' it moves the timer .5 seconds out.  The timer thus never fires
and never pats the watchdog for you.

1: http://git.chromium.org/gitweb/?p=chromiumos/third_party/daisydog.git

Signed-off-by: Doug Anderson <dianders@...omium.org>
Reviewed-by: Guenter Roeck <linux@...ck-us.net>
Tested-by: Jisheng Zhang <jszhang@...vell.com>
---
Changes in v2: None

 drivers/watchdog/dw_wdt.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/watchdog/dw_wdt.c b/drivers/watchdog/dw_wdt.c
index a284abd..6ea0634 100644
--- a/drivers/watchdog/dw_wdt.c
+++ b/drivers/watchdog/dw_wdt.c
@@ -215,6 +215,7 @@ static ssize_t dw_wdt_write(struct file *filp, const char __user *buf,
 	}
 
 	dw_wdt_set_next_heartbeat();
+	dw_wdt_keepalive();
 	mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT);
 
 	return len;
-- 
2.2.0.rc0.207.ga3a616c

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