From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1162301AbdEYA4U (ORCPT ); Wed, 24 May 2017 20:56:20 -0400 Received: from bh-25.webhostbox.net ([208.91.199.152]:39340 "EHLO bh-25.webhostbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1034024AbdEYA4O (ORCPT ); Wed, 24 May 2017 20:56:14 -0400 Subject: Re: [PATCH v5 2/3] watchdog: introduce watchdog.open_timeout commandline parameter To: Rasmus Villemoes , Wim Van Sebroeck , Jonathan Corbet Cc: Sebastian Reichel , esben.haabendal@gmail.com, linux-watchdog@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org References: <1495462000-28979-1-git-send-email-rasmus.villemoes@prevas.dk> <1495462000-28979-3-git-send-email-rasmus.villemoes@prevas.dk> From: Guenter Roeck Message-ID: Date: Wed, 24 May 2017 17:56:11 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.1.1 MIME-Version: 1.0 In-Reply-To: <1495462000-28979-3-git-send-email-rasmus.villemoes@prevas.dk> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Authenticated_sender: linux@roeck-us.net X-OutGoing-Spam-Status: No, score=-1.0 X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - bh-25.webhostbox.net X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - roeck-us.net X-Get-Message-Sender-Via: bh-25.webhostbox.net: authenticated_id: linux@roeck-us.net X-Authenticated-Sender: bh-25.webhostbox.net: linux@roeck-us.net X-Source: X-Source-Args: X-Source-Dir: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/22/2017 07:06 AM, Rasmus Villemoes wrote: > The watchdog framework takes care of feeding a hardware watchdog until > userspace opens /dev/watchdogN. If that never happens for some reason > (buggy init script, corrupt root filesystem or whatnot) but the kernel > itself is fine, the machine stays up indefinitely. This patch allows > setting an upper limit for how long the kernel will take care of the > watchdog, thus ensuring that the watchdog will eventually reset the > machine. > > This is particularly useful for embedded devices where some fallback > logic is implemented in the bootloader (e.g., use a different root > partition, boot from network, ...). > > The open timeout is also used as a maximum time for an application to > re-open /dev/watchdogN after closing it. > > A value of 0 (the default) means infinite timeout, preserving the > current behaviour. > > Signed-off-by: Rasmus Villemoes > --- > Documentation/watchdog/watchdog-parameters.txt | 9 +++++++++ > drivers/watchdog/watchdog_dev.c | 26 +++++++++++++++++++++++++- > 2 files changed, 34 insertions(+), 1 deletion(-) > > diff --git a/Documentation/watchdog/watchdog-parameters.txt b/Documentation/watchdog/watchdog-parameters.txt > index 914518a..4801ec6 100644 > --- a/Documentation/watchdog/watchdog-parameters.txt > +++ b/Documentation/watchdog/watchdog-parameters.txt > @@ -8,6 +8,15 @@ See Documentation/admin-guide/kernel-parameters.rst for information on > providing kernel parameters for builtin drivers versus loadable > modules. > > +The watchdog core currently understands one parameter, We have a second parameter queued, handle_boot_enabled. Please rephrase so we don't have to change the text with each new parameter. Thanks, Guenter > +watchdog.open_timeout. This is the maximum time, in milliseconds, for > +which the watchdog framework will take care of pinging a hardware > +watchdog until userspace opens the corresponding /dev/watchdogN > +device. A value of 0 (the default) means an infinite timeout. Setting > +this to a non-zero value can be useful to ensure that either userspace > +comes up properly, or the board gets reset and allows fallback logic > +in the bootloader to try something else. > + > > ------------------------------------------------- > acquirewdt: > diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c > index caa4b90..c807067 100644 > --- a/drivers/watchdog/watchdog_dev.c > +++ b/drivers/watchdog/watchdog_dev.c > @@ -66,6 +66,7 @@ struct watchdog_core_data { > struct mutex lock; > unsigned long last_keepalive; > unsigned long last_hw_keepalive; > + unsigned long open_deadline; > struct delayed_work work; > unsigned long status; /* Internal status bits */ > #define _WDOG_DEV_OPEN 0 /* Opened ? */ > @@ -80,6 +81,21 @@ static struct watchdog_core_data *old_wd_data; > > static struct workqueue_struct *watchdog_wq; > > +static unsigned open_timeout; > +module_param(open_timeout, uint, 0644); > + > +static bool watchdog_past_open_deadline(struct watchdog_core_data *data) > +{ > + if (!open_timeout) > + return false; > + return time_is_before_jiffies(data->open_deadline); > +} > + > +static void watchdog_set_open_deadline(struct watchdog_core_data *data) > +{ > + data->open_deadline = jiffies + msecs_to_jiffies(open_timeout); > +} > + > static inline bool watchdog_need_worker(struct watchdog_device *wdd) > { > /* All variables in milli-seconds */ > @@ -196,7 +212,13 @@ static bool watchdog_worker_should_ping(struct watchdog_core_data *wd_data) > { > struct watchdog_device *wdd = wd_data->wdd; > > - return wdd && (watchdog_active(wdd) || watchdog_hw_running(wdd)); > + if (!wdd) > + return false; > + > + if (watchdog_active(wdd)) > + return true; > + > + return watchdog_hw_running(wdd) && !watchdog_past_open_deadline(wd_data); > } > > static void watchdog_ping_work(struct work_struct *work) > @@ -857,6 +879,7 @@ static int watchdog_release(struct inode *inode, struct file *file) > watchdog_ping(wdd); > } > > + watchdog_set_open_deadline(wd_data); > watchdog_update_worker(wdd); > > /* make sure that /dev/watchdog can be re-opened */ > @@ -955,6 +978,7 @@ static int watchdog_cdev_register(struct watchdog_device *wdd, dev_t devno) > > /* Record time of most recent heartbeat as 'just before now'. */ > wd_data->last_hw_keepalive = jiffies - 1; > + watchdog_set_open_deadline(wd_data); > > /* > * If the watchdog is running, prevent its driver from being unloaded, >