Linux-Watchdog Archive on lore.kernel.org
 help / color / Atom feed
From: Dmitry Safonov <dima@arista.com>
To: linux-kernel@vger.kernel.org
Cc: Dmitry Safonov <0x7f454c46@gmail.com>,
	Dmitry Safonov <dima@arista.com>,
	Guenter Roeck <linux@roeck-us.net>,
	Wim Van Sebroeck <wim@linux-watchdog.org>,
	linux-watchdog@vger.kernel.org
Subject: [RFC 1/2] watchdog: Check WDOG_STOP_ON_REBOOT in reboot notifier
Date: Tue, 21 Jan 2020 16:21:44 +0000
Message-ID: <20200121162145.166334-2-dima@arista.com> (raw)
In-Reply-To: <20200121162145.166334-1-dima@arista.com>

Many watchdog drivers use watchdog_stop_on_reboot() helper in order
to stop the watchdog on system reboot. Unfortunately, this logic is
coded in driver's probe function and doesn't allows user to decide what
to do during shutdown/reboot.

On the other side, Xen and Qemu watchdog drivers (xen_wdt and i6300esb)
may be configured to either send NMI or turn off/reboot VM as
the watchdog action. As the kernel may stuck at any state, sending NMIs
can't reliably reboot the VM.

At Arista, we benefited from the following set-up: the emulated watchdogs
trigger VM reset and softdog is set to catch less severe conditions to
generate vmcore. Just before reboot watchdog's timeout is increased
to some good-enough value (3 mins). That keeps watchdog always running
and guarantees that VM doesn't stuck.

As a preparation to move the watchdog's decision to stop on reboot or
not in userspace, allow WDOG_STOP_ON_REBOOT to be set during runtime,
not only on driver's probing. Always register reboot notifier and check
WDOG_STOP_ON_REBOOT inside it (on actual reboot).

Signed-off-by: Dmitry Safonov <dima@arista.com>
---
 drivers/watchdog/watchdog_dev.c | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
index 4b2a85438478..8766dd93028f 100644
--- a/drivers/watchdog/watchdog_dev.c
+++ b/drivers/watchdog/watchdog_dev.c
@@ -1103,6 +1103,10 @@ static int watchdog_reboot_notifier(struct notifier_block *nb,
 	struct watchdog_device *wdd;
 
 	wdd = container_of(nb, struct watchdog_device, reboot_nb);
+
+	if (!test_bit(WDOG_STOP_ON_REBOOT, &wdd->status))
+		return NOTIFY_DONE;
+
 	if (code == SYS_DOWN || code == SYS_HALT) {
 		if (watchdog_active(wdd)) {
 			int ret;
@@ -1139,16 +1143,13 @@ int watchdog_dev_register(struct watchdog_device *wdd)
 		return ret;
 	}
 
-	if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status)) {
-		wdd->reboot_nb.notifier_call = watchdog_reboot_notifier;
+	wdd->reboot_nb.notifier_call = watchdog_reboot_notifier;
 
-		ret = devm_register_reboot_notifier(&wdd->wd_data->dev,
-						    &wdd->reboot_nb);
-		if (ret) {
-			pr_err("watchdog%d: Cannot register reboot notifier (%d)\n",
-			       wdd->id, ret);
-			watchdog_dev_unregister(wdd);
-		}
+	ret = devm_register_reboot_notifier(&wdd->wd_data->dev, &wdd->reboot_nb);
+	if (ret) {
+		pr_err("watchdog%d: Cannot register reboot notifier (%d)\n",
+				wdd->id, ret);
+		watchdog_dev_unregister(wdd);
 	}
 
 	return ret;
-- 
2.25.0


  reply index

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-21 16:21 [RFC 0/2] watchdog: Provide user control over WDOG_STOP_ON_REBOOT Dmitry Safonov
2020-01-21 16:21 ` Dmitry Safonov [this message]
2020-01-21 16:21 ` [RFC 2/2] watchdog/uapi: Add WDIOS_{RUN,STOP}_ON_REBOOT Dmitry Safonov

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200121162145.166334-2-dima@arista.com \
    --to=dima@arista.com \
    --cc=0x7f454c46@gmail.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-watchdog@vger.kernel.org \
    --cc=linux@roeck-us.net \
    --cc=wim@linux-watchdog.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-Watchdog Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-watchdog/0 linux-watchdog/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-watchdog linux-watchdog/ https://lore.kernel.org/linux-watchdog \
		linux-watchdog@vger.kernel.org
	public-inbox-index linux-watchdog

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-watchdog


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git