From: Tzung-Bi Shih <tzungbi@kernel.org>
To: Guenter Roeck <linux@roeck-us.net>
Cc: linux-watchdog@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 8/8] watchdog: core: Update last_keepalive in watchdog_start()
Date: Wed, 30 Sep 2026 19:54:49 +0800 [thread overview]
Message-ID: <arz4iU0SQDRDFMjU@tzungbi-laptop> (raw)
In-Reply-To: <20260929134635.2567137-9-linux@roeck-us.net>
On Tue, Sep 29, 2026 at 06:46:35AM -0700, Guenter Roeck wrote:
> When starting a watchdog whose hardware is already running,
> watchdog_start() calls __watchdog_ping() before marking the watchdog
> active, and fails to update wd_data->last_keepalive. As a result:
>
> 1. wd_data->last_keepalive remains 0, causing watchdog_get_timeleft() to
> calculate the elapsed time since the epoch and return 0 time left.
> 2. watchdog_update_worker() inside __watchdog_ping() evaluates
> watchdog_need_worker() and watchdog_next_keepalive() while WDOG_ACTIVE
> is still clear, using wd_data->open_deadline instead of
> wd_data->last_keepalive. If open_deadline has expired, the background
> keepalive timer is not armed; conversely, if the active watchdog does
> not need a worker, the boot keepalive timer is not canceled.
>
> Set WDOG_ACTIVE and wd_data->last_keepalive to started_at before calling
> __watchdog_ping(), and revert WDOG_ACTIVE and update the worker if
> __watchdog_ping() fails.
>
> Fixes: fbbe35dfcf94 ("watchdog: use __watchdog_ping in startup")
> Assisted-by: LLM
> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Tzung-Bi Shih <tzungbi@kernel.org>
prev parent reply other threads:[~2026-09-30 11:54 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-29 13:46 [PATCH 0/8] watchdog: core: Fix locking, lifetime, suspend, and state management bugs Guenter Roeck
2026-09-29 13:46 ` [PATCH 1/8] watchdog: core: Clear wd_data pointer on errors Guenter Roeck
2026-09-30 11:53 ` Tzung-Bi Shih
2026-09-29 13:46 ` [PATCH 2/8] watchdog: core: Add missing locks Guenter Roeck
2026-09-30 11:53 ` Tzung-Bi Shih
2026-09-29 13:46 ` [PATCH 3/8] watchdog: core: Prevent ping worker from re-arming timer on suspend Guenter Roeck
2026-09-30 11:53 ` Tzung-Bi Shih
2026-09-29 13:46 ` [PATCH 4/8] watchdog: core: Stop pretimeout hrtimer " Guenter Roeck
2026-09-30 11:54 ` Tzung-Bi Shih
2026-09-29 13:46 ` [PATCH 5/8] watchdog: core: Restore WDOG_HW_RUNNING if stopping watchdog fails Guenter Roeck
2026-09-30 11:54 ` Tzung-Bi Shih
2026-09-30 12:37 ` Guenter Roeck
2026-09-29 13:46 ` [PATCH 6/8] watchdog: core: Cancel timer if cdev_device_add() fails Guenter Roeck
2026-09-30 11:54 ` Tzung-Bi Shih
2026-09-29 13:46 ` [PATCH 7/8] watchdog: core: Fix unbalanced module_put() in watchdog_open() Guenter Roeck
2026-09-30 11:54 ` Tzung-Bi Shih
2026-09-29 13:46 ` [PATCH 8/8] watchdog: core: Update last_keepalive in watchdog_start() Guenter Roeck
2026-09-30 11:54 ` Tzung-Bi Shih [this message]
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