Messages in this thread | | | Date | Mon, 26 Apr 2021 08:28:01 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH v10 clocksource 1/7] clocksource: Provide module parameters to inject delays in watchdog |
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On Sun, Apr 25, 2021 at 09:07:36PM -0700, Andi Kleen wrote:
[ . . . ]
> > + clocksource.inject_delay_period= [KNL] > > + Number of calls to clocksource_watchdog() before > > + delays are injected between reads from the > > + two clocksources. Values of zero disable this > > + delay injection. These delays can cause clocks > > + to be marked unstable, so use of this parameter > > + should therefore be avoided on production systems. > > + Defaults to zero (disabled). > > + > > + clocksource.inject_delay_repeat= [KNL] > > + Number of repeated clocksource_watchdog() delay > > + injections per period. If inject_delay_period > > + is five and inject_delay_repeat is three, there > > + will be five delay-free reads followed by three > > + delayed reads. > > I'm not sure command line options are the right way to do this. > How about integrating it with the fault injection framework in debugfs. > > This way syzkaller etc. can play with it, which long term would > give much better test coverage. > > This wouldn't allow boot time coverage, but presumably that's not > too important here.
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.
Thanx, Paul
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