Re: [PATCH 9/9] watchdog: skip checks when panic is in progress

[Jinchao Wang]

On 8/20/25 23:18, Yury Norov wrote:
> On Wed, Aug 20, 2025 at 05:14:54PM +0800, Jinchao Wang wrote:
> > Both watchdog_buddy_check_hardlockup() and
> > watchdog_overflow_callback() may trigger
> > during a panic. This can lead to recursive
> > panic handling.
> >
> > Add panic_in_progress() checks so watchdog
> > activity is skipped once a panic has begun.
> >
> > This prevents recursive panic and keeps the
> > panic path more reliable.
> >
> > Signed-off-by: Jinchao Wang <wangjinchao600@xxxxxxxxx>
> > ---
> >   kernel/watchdog_buddy.c | 5 +++++
> >   kernel/watchdog_perf.c  | 3 +++
> >   2 files changed, 8 insertions(+)
> >
> > diff --git a/kernel/watchdog_buddy.c b/kernel/watchdog_buddy.c
> > index ee754d767c21..79a85623028c 100644
> > --- a/kernel/watchdog_buddy.c
> > +++ b/kernel/watchdog_buddy.c
> > @@ -93,6 +93,11 @@ void watchdog_buddy_check_hardlockup(int hrtimer_interrupts)
> >   	 */
> >   	if (hrtimer_interrupts % 3 != 0)
> >   		return;
> > +	/*
> > +	 * pass the buddy check if a panic is in process
> > +	 */
> > +	if (panic_in_progress())
> > +		return;
> >   
> >   	/* check for a hardlockup on the next CPU */
> >   	next_cpu = watchdog_next_cpu(smp_processor_id());
> > diff --git a/kernel/watchdog_perf.c b/kernel/watchdog_perf.c
> > index 9c58f5b4381d..7641de750ca5 100644
> > --- a/kernel/watchdog_perf.c
> > +++ b/kernel/watchdog_perf.c
> > @@ -12,6 +12,7 @@
> >   
> >   #define pr_fmt(fmt) "NMI watchdog: " fmt
> >   
> > +#include <linux/panic.h>
> >   #include <linux/nmi.h>
> >   #include <linux/atomic.h>
> >   #include <linux/module.h>
> > @@ -110,6 +111,8 @@ static void watchdog_overflow_callback(struct perf_event *event,
> >   
> >   	if (!watchdog_check_timestamp())
> >   		return;
> > +	if (panic_in_progress())
> > +		return;
>
> It looks like watchdog_check_timestamp() does some real work, like
> updates last_timestamp and so on. Under the panic condition all this
> may be unreliable, right?
>
> Maybe it's worth to make panic_in_progress() the first check in the
> chain?
That's a good point. Thank you.
> With that,
>
> Reviewed-by: Yury Norov (NVIDIA) <yury.norov@xxxxxxxxx>
>
> >   
> >   	watchdog_hardlockup_check(smp_processor_id(), regs);
> >   }
> > --
> > 2.43.0


--
Best regards,
Jinchao