Messages in this thread | | | From | Luming Yu <> | Date | Wed, 28 Apr 2021 12:49:12 +0800 | Subject | Re: [PATCH v10 clocksource 1/7] clocksource: Provide module parameters to inject delays in watchdog |
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We 'd expect to see clock_source watchdog can avoid to do wrong thing due to the injected delay or in real life delay by doing tsc sync-re-check by applying the patch-set. However , the noise is still cause wrong actions and the patch doesn't defeat the injected's delay please correct me if I'm wrong.
parameters]# cat * 1 1 -1 3 8
[62939.809615] clocksource: clocksource_watchdog_inject_delay(): Injecting delay. [62939.816867] clocksource: clocksource_watchdog_inject_delay(): Injecting delay. [62939.824094] clocksource: clocksource_watchdog_inject_delay(): Injecting delay. [62939.831314] clocksource: clocksource_watchdog_inject_delay(): Injecting delay. [62939.838536] clocksource: timekeeping watchdog on CPU26: hpet read-back delay of 7220833ns, attempt 4, marking unstable [62939.849230] tsc: Marking TSC unstable due to clocksource watchdog [62939.855340] TSC found unstable after boot, most likely due to broken BIOS. Use 'tsc=unstable'. [62939.863972] sched_clock: Marking unstable (62943398530130, -3543150114)<-(62941186607503, -1331276112) [62939.875104] clocksource: Checking clocksource tsc synchronization from CPU 123 to CPUs 0,6,26,62,78,97-98,137. [62939.886518] clocksource: Switched to clocksource hpet
On Tue, Apr 27, 2021 at 2:27 AM Paul E. McKenney <paulmck@kernel.org> wrote: > > On Mon, Apr 26, 2021 at 10:56:27AM -0700, Andi Kleen wrote: > > > ------------------------------------------------------------------------ > > > > > > - 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. > > > > > > I disagree with this recommendation because it prevents fuzzer coverage. > > > > Much better to have an uniform interface that can be automatically > > explored. > > The permissions for these module parameters is 0644, so there is no > reason why the fuzzers cannot use them via sysfs. > > Thanx, Paul
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