Messages in this thread | | | Subject | Re: [PATCH clocksource 4/5] clocksource: Provide a module parameter to fuzz per-CPU clock checking | From | Randy Dunlap <> | Date | Tue, 2 Feb 2021 11:51:02 -0800 |
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On 2/2/21 9:06 AM, paulmck@kernel.org wrote: > From: "Paul E. McKenney" <paulmck@kernel.org> > > Code that checks for clock desynchronization must itself be tested, so > this commit creates a new clocksource.inject_delay_shift_percpu= kernel > boot parameter that adds or subtracts a large value from the check read, > using the specified bit of the CPU ID to determine whether to add or > to subtract. > > Cc: John Stultz <john.stultz@linaro.org> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Stephen Boyd <sboyd@kernel.org> > Cc: Jonathan Corbet <corbet@lwn.net> > Cc: Mark Rutland <Mark.Rutland@arm.com> > Cc: Marc Zyngier <maz@kernel.org> > Cc: Andi Kleen <ak@linux.intel.com> > Reported-by: Chris Mason <clm@fb.com> > Signed-off-by: Paul E. McKenney <paulmck@kernel.org> > --- > Documentation/admin-guide/kernel-parameters.txt | 9 +++++++++ > kernel/time/clocksource.c | 10 +++++++++- > 2 files changed, 18 insertions(+), 1 deletion(-) > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > index 9965266..f561e94 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -593,6 +593,15 @@ > times the value specified for inject_delay_freq > of consecutive non-delays. > > + clocksource.inject_delay_shift_percpu= [KNL] > + Shift count to obtain bit from CPU number to > + determine whether to shift the time of the per-CPU > + clock under test ahead or behind. For example,
It's a good think that you give an example -- it helps a little bit. That sentence above needs to be rewritten...
> + setting this to the value four will result in > + alternating groups of 16 CPUs shifting ahead and > + the rest of the CPUs shifting behind. The default > + value of -1 disable this type of error injection.
disables
> + > clocksource.max_read_retries= [KNL] > Number of clocksource_watchdog() retries due to > external delays before the clock will be marked
-- ~Randy
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