linux-kernel - Re: [PATCH v10 clocksource 1/7] clocksource: Provide module parameters to inject delays in watchdog

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Message-ID: <20210426161425.GC975577@paulmck-ThinkPad-P17-Gen-1>
Date:   Mon, 26 Apr 2021 09:14:25 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Andi Kleen <ak@...ux.intel.com>
Cc:     tglx@...utronix.de, linux-kernel@...r.kernel.org,
        john.stultz@...aro.org, sboyd@...nel.org, corbet@....net,
        Mark.Rutland@....com, maz@...nel.org, kernel-team@...com,
        neeraju@...eaurora.org, feng.tang@...el.com,
        zhengjun.xing@...el.com, Chris Mason <clm@...com>
Subject: Re: [PATCH v10 clocksource 1/7] clocksource: Provide module
 parameters to inject delays in watchdog

On Mon, Apr 26, 2021 at 09:00:08AM -0700, Andi Kleen wrote:
> > Boot-time coverage is important, as we saw in kbuild test robot testing
> > of v9 of this patchset, which triggered clocksource_tsc_early, but not
> > clocksource_tsc.  Note that v10 avoids this triggering.
> 
> Not sure how that could happen, I didn't think the kbuild bot knows
> how to set these options.

It didn't need to.  My initial choice of maximum skew in the v9 patch
series exceeded what clocksource_tsc_early could remain within, given its
quick calibration.  In v10 of this patch series, clocksource_tsc_early
is given special dispensation.

> Overall I think you should follow the existing frame works instead
> of inventing your own so that things can be later tested in an
> uniform manner.
> 
> Perhaps the fault injection framework needs boot options, but
> they should be generic.

>From Documentation/fault-injection/fault-injection.rst:

------------------------------------------------------------------------

- module parameters

  If the scope of the fault injection capability is limited to a
  single kernel module, it is better to provide module parameters to
  configure the fault attributes.

------------------------------------------------------------------------

And in this case, the fault injection capability is in fact limited to
kernel/clocksource.c.

							Thanx, Paul