Re: [PATCHv5 3/3] watchdog/softlockup: add SOFTLOCKUP_DETECTOR_INTR_STORM Kconfig knob

[Bitao Hu]

On 2024/2/7 05:42, Doug Anderson wrote:
> Hi,
>
> On Tue, Feb 6, 2024 at 1:59 AM Bitao Hu <yaoma@xxxxxxxxxxxxxxxxx> wrote:
> > The interrupt storm detection mechanism we implemented requires a
> > considerable amount of global storage space when configured for
> > the maximum number of CPUs.
> > Therefore, adding a SOFTLOCKUP_DETECTOR_INTR_STORM Kconfig knob that
> > defaults to "yes" if the max number of CPUs is <= 128.
> >
> > Signed-off-by: Bitao Hu <yaoma@xxxxxxxxxxxxxxxxx>
> > ---
> >   kernel/watchdog.c |  2 +-
> >   lib/Kconfig.debug | 13 +++++++++++++
> >   2 files changed, 14 insertions(+), 1 deletion(-)
>
> IMO this should be squashed into patch #1, though I won't insist.
Agree.
> > diff --git a/kernel/watchdog.c b/kernel/watchdog.c
> > index 26dc1ad86276..1595e4a94774 100644
> > --- a/kernel/watchdog.c
> > +++ b/kernel/watchdog.c
> > @@ -338,7 +338,7 @@ __setup("watchdog_thresh=", watchdog_thresh_setup);
> >
> >   static void __lockup_detector_cleanup(void);
> >
> > -#ifdef CONFIG_IRQ_TIME_ACCOUNTING
> > +#ifdef CONFIG_SOFTLOCKUP_DETECTOR_INTR_STORM
> >   #define NUM_STATS_GROUPS       5
> >   #define NUM_STATS_PER_GROUP    4
> >   enum stats_per_group {
> > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> > index 975a07f9f1cc..74002ba7c42d 100644
> > --- a/lib/Kconfig.debug
> > +++ b/lib/Kconfig.debug
> > @@ -1029,6 +1029,19 @@ config SOFTLOCKUP_DETECTOR
> >            chance to run.  The current stack trace is displayed upon
> >            detection and the system will stay locked up.
> >
> > +config SOFTLOCKUP_DETECTOR_INTR_STORM
> > +       bool "Detect Interrupt Storm in Soft Lockups"
> > +       depends on SOFTLOCKUP_DETECTOR && IRQ_TIME_ACCOUNTING
> > +       default y if NR_CPUS <= 128
> > +       help
> > +         Say Y here to enable the kernel to detect interrupt storm
> > +         during "soft lockups".
> > +
> > +         "soft lockups" can be caused by a variety of reasons. If one is caused by
> > +         an interrupt storm, then the storming interrupts will not be on the
> > +         callstack. To detect this case, it is necessary to report the CPU stats
> > +         and the interrupt counts during the "soft lockups".
>
> It's probably not terribly important, but I notice that the other help
> text in this file is generally wrapped to 80 columns. Even though the
> kernel has relaxed the 80 column rule a bit, it still feels like this
> could easily be wrapped to 80 columns without sacrificing any
> readability.
OK.
> In any case:
>
> Reviewed-by: Douglas Anderson <dianders@xxxxxxxxxxxx>