Re: [PATCH v2 2/2] watchdog: dw_wdt: keepalive the watchdog at write time

Dmitry Torokhov
2015-05-08T05:24:08Z

On Thu, May 07, 2015 at 09:27:45PM -0700, Doug Anderson wrote:
> 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@chromium.org>
> Reviewed-by: Guenter Roeck <linux@roeck-us.net>
> Tested-by: Jisheng Zhang <jszhang@marvell.com>

Reviewed-by: Dmitry Torokhov <dmitry.torokhov@gmail.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
>

--
Dmitry