From: Randy Dunlap <rdunlap@infradead.org>
To: paulmck@kernel.org
Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com,
john.stultz@linaro.org, tglx@linutronix.de, sboyd@kernel.org,
corbet@lwn.net, Mark.Rutland@arm.com, maz@kernel.org,
ak@linux.intel.com, clm@fb.com
Subject: Re: [PATCH clocksource 4/5] clocksource: Provide a module parameter to fuzz per-CPU clock checking
Date: Tue, 2 Feb 2021 17:31:55 -0800 [thread overview]
Message-ID: <b878262a-4c98-91bd-eb88-456a869dc9e1@infradead.org> (raw)
In-Reply-To: <20210203005020.GI2743@paulmck-ThinkPad-P72>
On 2/2/21 4:50 PM, Paul E. McKenney wrote:
> On Tue, Feb 02, 2021 at 11:51:02AM -0800, Randy Dunlap wrote:
>> 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...
>
> That is a bit obscure, now that you mention it.
>
>>> + 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
>
> Good eyes!
>
> So how about like this?
Much better, thanks.
> clocksource.inject_delay_shift_percpu= [KNL]
> Clocksource delay injection partitions the CPUs
> into two sets, one whose clocks are moved ahead
> and the other whose clocks are moved behind.
> This kernel parameter selects the CPU-number
> bit that determines which of these two sets the
> corresponding CPU is placed into. For example,
> setting this parameter to the value four will
I know that in "writing," "four" should be written out as you have it,
but IMO using "4" here would be much better. FWIW.
> result in the first set containing alternating
> groups of 16 CPUs whose clocks are moved ahead,
> while the second set will contain the rest of
> the CPUs, whose clocks are moved behind.
>
> The default value of -1 disables this type of
> error injection.
>
> Thanx, Paul
>
>>> +
>>> clocksource.max_read_retries= [KNL]
>>> Number of clocksource_watchdog() retries due to
>>> external delays before the clock will be marked
thanks!
--
~Randy
next prev parent reply other threads:[~2021-02-03 1:33 UTC|newest]
Thread overview: 72+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-06 0:40 [PATCH RFC clocksource] Do not mark clocks unstable due to delays Paul E. McKenney
2021-01-06 0:41 ` [PATCH RFC clocksource 1/5] clocksource: Provide module parameters to inject delays in watchdog paulmck
2021-01-06 0:41 ` [PATCH RFC clocksource 2/5] clocksource: Retry clock read if long delays detected paulmck
2021-01-06 16:28 ` Rik van Riel
2021-01-06 19:53 ` Paul E. McKenney
2021-01-06 20:59 ` Rik van Riel
2021-01-06 0:41 ` [PATCH RFC clocksource 3/5] clocksource: Check per-CPU clock synchronization when marked unstable paulmck
2021-01-06 0:41 ` [PATCH RFC clocksource 4/5] clocksource: Provide a module parameter to fuzz per-CPU clock checking paulmck
2021-01-06 0:41 ` [PATCH RFC clocksource 5/5] clocksource: Do pairwise clock-desynchronization checking paulmck
2021-01-12 0:42 ` [PATCH v2 clocksource] Do not mark clocks unstable due to delays Paul E. McKenney
2021-01-12 0:45 ` [PATCH v2 clocksource 1/5] clocksource: Provide module parameters to inject delays in watchdog paulmck
2021-01-12 0:45 ` [PATCH v2 clocksource 2/5] clocksource: Retry clock read if long delays detected paulmck
2021-01-12 0:45 ` [PATCH v2 clocksource 3/5] clocksource: Check per-CPU clock synchronization when marked unstable paulmck
2021-01-12 0:45 ` [PATCH v2 clocksource 4/5] clocksource: Provide a module parameter to fuzz per-CPU clock checking paulmck
2021-01-12 0:45 ` [PATCH v2 clocksource 5/5] clocksource: Do pairwise clock-desynchronization checking paulmck
2021-02-02 17:04 ` [PATCH v3 clocksource] Do not mark clocks unstable due to delays Paul E. McKenney
2021-02-02 17:06 ` [PATCH clocksource 1/5] clocksource: Provide module parameters to inject delays in watchdog paulmck
2021-02-02 17:06 ` [PATCH clocksource 2/5] clocksource: Retry clock read if long delays detected paulmck
2021-02-02 17:06 ` [PATCH clocksource 3/5] clocksource: Check per-CPU clock synchronization when marked unstable paulmck
2021-02-02 17:06 ` [PATCH clocksource 4/5] clocksource: Provide a module parameter to fuzz per-CPU clock checking paulmck
2021-02-02 19:51 ` Randy Dunlap
2021-02-03 0:50 ` Paul E. McKenney
2021-02-03 1:31 ` Randy Dunlap [this message]
2021-02-03 1:40 ` Paul E. McKenney
2021-02-02 17:06 ` [PATCH clocksource 5/5] clocksource: Do pairwise clock-desynchronization checking paulmck
2021-02-17 21:28 ` [PATCH v3 clocksource] Do not mark clocks unstable due to delays Paul E. McKenney
2021-02-17 21:29 ` [PATCH clocksource 1/5] clocksource: Provide module parameters to inject delays in watchdog paulmck
2021-02-17 21:29 ` [PATCH clocksource 2/5] clocksource: Retry clock read if long delays detected paulmck
2021-02-17 21:29 ` [PATCH clocksource 3/5] clocksource: Check per-CPU clock synchronization when marked unstable paulmck
2021-02-17 21:29 ` [PATCH clocksource 4/5] clocksource: Provide a module parameter to fuzz per-CPU clock checking paulmck
2021-02-17 21:29 ` [PATCH clocksource 5/5] clocksource: Do pairwise clock-desynchronization checking paulmck
2021-03-04 0:49 ` [PATCH v5 clocksource] Do not mark clocks unstable due to delays for v5.13 Paul E. McKenney
2021-03-04 0:53 ` [PATCH kernel/time 1/5] clocksource: Provide module parameters to inject delays in watchdog paulmck
2021-03-04 0:53 ` [PATCH kernel/time 2/5] clocksource: Retry clock read if long delays detected paulmck
2021-03-04 0:53 ` [PATCH kernel/time 3/5] clocksource: Check per-CPU clock synchronization when marked unstable paulmck
2021-03-04 0:53 ` [PATCH kernel/time 4/5] clocksource: Provide a module parameter to fuzz per-CPU clock checking paulmck
2021-03-04 0:53 ` [PATCH kernel/time 5/5] clocksource: Do pairwise clock-desynchronization checking paulmck
2021-04-02 20:29 ` [PATCH v5 clocksource] Do not mark clocks unstable due to delays for v5.13 Paul E. McKenney
2021-04-02 20:31 ` [PATCH v6 clocksource] Do not mark clocks unstable dueclocksource: Provide module parameters to inject delays in watchdog paulmck
2021-04-02 22:22 ` Thomas Gleixner
2021-04-02 22:37 ` Paul E. McKenney
2021-04-02 22:48 ` [PATCH v7 clocksource] Do not mark clocks unstable due to delays for v5.13 Paul E. McKenney
2021-04-02 22:49 ` [PATCH v7 clocksource 1/5] clocksource: Provide module parameters to inject delays in watchdog paulmck
2021-04-02 22:49 ` [PATCH v7 clocksource 2/5] clocksource: Retry clock read if long delays detected paulmck
2021-04-10 8:41 ` Thomas Gleixner
2021-04-10 23:50 ` Paul E. McKenney
2021-04-02 22:49 ` [PATCH v7 clocksource 3/5] clocksource: Check per-CPU clock synchronization when marked unstable paulmck
2021-04-10 9:00 ` Thomas Gleixner
2021-04-11 0:20 ` Paul E. McKenney
2021-04-11 10:33 ` Thomas Gleixner
2021-04-11 16:46 ` Paul E. McKenney
2021-04-12 4:21 ` Paul E. McKenney
2021-04-12 13:08 ` Thomas Gleixner
2021-04-12 18:20 ` Paul E. McKenney
2021-04-12 18:54 ` Thomas Gleixner
2021-04-12 19:57 ` Paul E. McKenney
2021-04-12 20:37 ` Thomas Gleixner
2021-04-12 23:18 ` Paul E. McKenney
2021-04-13 20:49 ` Thomas Gleixner
2021-04-14 4:48 ` Paul E. McKenney
2021-04-02 22:49 ` [PATCH v7 clocksource 4/5] clocksource: Provide a module parameter to fuzz per-CPU clock checking paulmck
2021-04-02 22:49 ` [PATCH v7 clocksource 5/5] clocksource: Do pairwise clock-desynchronization checking paulmck
2021-04-10 9:04 ` Thomas Gleixner
2021-04-11 0:21 ` Paul E. McKenney
2021-04-10 8:01 ` [PATCH v7 clocksource] Do not mark clocks unstable due to delays for v5.13 Thomas Gleixner
2021-04-10 23:26 ` Paul E. McKenney
2021-04-11 10:58 ` Thomas Gleixner
2021-04-11 16:50 ` Paul E. McKenney
2021-04-02 20:31 ` [PATCH v6 clocksource] Do not mark clocks unstable dueclocksource: Retry clock read if long delays detected paulmck
2021-04-02 20:31 ` [PATCH v6 clocksource] Do not mark clocks unstable dueclocksource: Check per-CPU clock synchronization when marked unstable paulmck
2021-04-02 20:31 ` [PATCH v6 clocksource] Do not mark clocks unstable dueclocksource: Provide a module parameter to fuzz per-CPU clock checking paulmck
2021-04-02 20:31 ` [PATCH v6 clocksource] Do not mark clocks unstable dueclocksource: Do pairwise clock-desynchronization checking paulmck
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