| Message ID | 20200223114939.194754-1-dima@arista.com (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
| Series | [PATCHv3] watchdog: Add stop_on_reboot parameter to control reboot policy | expand |
On 2/23/20 3:49 AM, Dmitry Safonov wrote: > 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. > > Provide new stop_on_reboot module parameter to let user control > watchdog's reboot policy. > > Cc: Guenter Roeck <linux@roeck-us.net> > Cc: Wim Van Sebroeck <wim@linux-watchdog.org> > Cc: linux-watchdog@vger.kernel.org > Signed-off-by: Dmitry Safonov <dima@arista.com> Reviewed-by: Guenter Roeck <linux@roeck-us.net> > --- > Changes: > v3: Make module parameter read-only in runtime (Thanks Guenter for > spotting the typo!) > v2: Add module parameter instead of ioctl() > > drivers/watchdog/watchdog_core.c | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > > diff --git a/drivers/watchdog/watchdog_core.c b/drivers/watchdog/watchdog_core.c > index 861daf4f37b2..423844757812 100644 > --- a/drivers/watchdog/watchdog_core.c > +++ b/drivers/watchdog/watchdog_core.c > @@ -39,6 +39,10 @@ > > static DEFINE_IDA(watchdog_ida); > > +static int stop_on_reboot = -1; > +module_param(stop_on_reboot, int, 0444); > +MODULE_PARM_DESC(stop_on_reboot, "Stop watchdogs on reboot (0=keep watching, 1=stop)"); > + > /* > * Deferred Registration infrastructure. > * > @@ -254,6 +258,14 @@ static int __watchdog_register_device(struct watchdog_device *wdd) > } > } > > + /* Module parameter to force watchdog policy on reboot. */ > + if (stop_on_reboot != -1) { > + if (stop_on_reboot) > + set_bit(WDOG_STOP_ON_REBOOT, &wdd->status); > + else > + clear_bit(WDOG_STOP_ON_REBOOT, &wdd->status); > + } > + > if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status)) { > wdd->reboot_nb.notifier_call = watchdog_reboot_notifier; > >
diff --git a/drivers/watchdog/watchdog_core.c b/drivers/watchdog/watchdog_core.c index 861daf4f37b2..423844757812 100644 --- a/drivers/watchdog/watchdog_core.c +++ b/drivers/watchdog/watchdog_core.c @@ -39,6 +39,10 @@ static DEFINE_IDA(watchdog_ida); +static int stop_on_reboot = -1; +module_param(stop_on_reboot, int, 0444); +MODULE_PARM_DESC(stop_on_reboot, "Stop watchdogs on reboot (0=keep watching, 1=stop)"); + /* * Deferred Registration infrastructure. * @@ -254,6 +258,14 @@ static int __watchdog_register_device(struct watchdog_device *wdd) } } + /* Module parameter to force watchdog policy on reboot. */ + if (stop_on_reboot != -1) { + if (stop_on_reboot) + set_bit(WDOG_STOP_ON_REBOOT, &wdd->status); + else + clear_bit(WDOG_STOP_ON_REBOOT, &wdd->status); + } + if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status)) { wdd->reboot_nb.notifier_call = watchdog_reboot_notifier;
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. Provide new stop_on_reboot module parameter to let user control watchdog's reboot policy. Cc: Guenter Roeck <linux@roeck-us.net> Cc: Wim Van Sebroeck <wim@linux-watchdog.org> Cc: linux-watchdog@vger.kernel.org Signed-off-by: Dmitry Safonov <dima@arista.com> --- Changes: v3: Make module parameter read-only in runtime (Thanks Guenter for spotting the typo!) v2: Add module parameter instead of ioctl() drivers/watchdog/watchdog_core.c | 12 ++++++++++++ 1 file changed, 12 insertions(+)