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From: Thomas Gleixner <tglx@linutronix.de>
To: Feng Tang <feng.tang@intel.com>, "Paul E. McKenney" <paulmck@kernel.org>
Cc: linux-kernel@vger.kernel.org, john.stultz@linaro.org,
	sboyd@kernel.org, corbet@lwn.net, Mark.Rutland@arm.com,
	maz@kernel.org, kernel-team@fb.com, neeraju@codeaurora.org,
	ak@linux.intel.com, zhengjun.xing@intel.com,
	Xing Zhengjun <zhengjun.xing@linux.intel.com>
Subject: Re: [PATCH v10 clocksource 6/7] clocksource: Forgive tsc_early pre-calibration drift
Date: Mon, 26 Apr 2021 17:28:37 +0200	[thread overview]
Message-ID: <87a6plt68q.ffs@nanos.tec.linutronix.de> (raw)
In-Reply-To: <20210426150127.GB23119@shbuild999.sh.intel.com>

On Mon, Apr 26 2021 at 23:01, Feng Tang wrote:
> On Sun, Apr 25, 2021 at 03:47:07PM -0700, Paul E. McKenney wrote:
> We've reported one case that tsc can be wrongly judged as 'unstable'
> by 'refined-jiffies' watchdog [1], while reducing the threshold could
> make it easier to be triggered.
>
> It could be reproduced on the a plaform with a 115200 serial console,
> and hpet been disabled (several x86 platforms has this), add 
> 'initcall_debug' cmdline parameter to get more debug message, we can
> see:
>
> [    1.134197] clocksource: timekeeping watchdog on CPU1: Marking clocksource 'tsc-early' as unstable because the skew is too large:
> [    1.134214] clocksource:                       'refined-jiffies' wd_nesc: 500000000 wd_now: ffff8b35 wd_last: ffff8b03 mask: ffffffff
> [    1.134217] clocksource:                       'tsc-early' cs_nsec: 507537855 cs_now: 4e63c9d09 cs_last: 4bebd81f5 mask: ffffffffffffffff
> [    1.134220] clocksource:                       No current clocksource.
> [    1.134222] tsc: Marking TSC unstable due to clocksource watchdog

Yes, refined jiffies is the worst case.

Though the worst of everything is that any of this exists at all, but
you knew that already :)

Thanks,

        tglx

  parent reply	other threads:[~2021-04-26 15:28 UTC|newest]

Thread overview: 72+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-25 22:45 [PATCH v10 clocksource 0/7] Do not mark clocks unstable due to delays for v5.13 Paul E. McKenney
2021-04-25 22:47 ` [PATCH v10 clocksource 1/7] clocksource: Provide module parameters to inject delays in watchdog Paul E. McKenney
2021-04-26  4:07   ` Andi Kleen
2021-04-26  7:13     ` Thomas Gleixner
2021-04-26 15:28     ` Paul E. McKenney
2021-04-26 16:00       ` Andi Kleen
2021-04-26 16:14         ` Paul E. McKenney
2021-04-26 17:56           ` Andi Kleen
2021-04-26 18:24             ` Paul E. McKenney
2021-04-28  4:49               ` Luming Yu
2021-04-28 13:57                 ` Paul E. McKenney
2021-04-28 14:24                   ` Luming Yu
2021-04-28 14:37                     ` Thomas Gleixner
2021-04-25 22:47 ` [PATCH v10 clocksource 2/7] clocksource: Retry clock read if long delays detected Paul E. McKenney
2021-04-27  1:44   ` Feng Tang
2021-04-25 22:47 ` [PATCH v10 clocksource 3/7] clocksource: Check per-CPU clock synchronization when marked unstable Paul E. McKenney
2021-04-26  4:12   ` Andi Kleen
2021-04-26  7:16     ` Thomas Gleixner
2021-04-25 22:47 ` [PATCH v10 clocksource 4/7] clocksource: Provide a module parameter to fuzz per-CPU clock checking Paul E. McKenney
2021-04-25 22:47 ` [PATCH v10 clocksource 5/7] clocksource: Limit number of CPUs checked for clock synchronization Paul E. McKenney
2021-04-25 22:47 ` [PATCH v10 clocksource 6/7] clocksource: Forgive tsc_early pre-calibration drift Paul E. McKenney
2021-04-26 15:01   ` Feng Tang
2021-04-26 15:25     ` Paul E. McKenney
2021-04-26 15:36       ` Feng Tang
2021-04-26 18:26         ` Paul E. McKenney
2021-04-27  1:13           ` Feng Tang
2021-04-27  3:46             ` Paul E. McKenney
2021-04-27  4:16               ` Feng Tang
2021-04-26 15:28     ` Thomas Gleixner [this message]
2021-04-27 21:03     ` Thomas Gleixner
2021-04-27  7:27   ` [clocksource] 8c30ace35d: WARNING:at_kernel/time/clocksource.c:#clocksource_watchdog kernel test robot
2021-04-27  7:27     ` kernel test robot
2021-04-27  8:45     ` Feng Tang
2021-04-27  8:45       ` Feng Tang
2021-04-27 13:37       ` Paul E. McKenney
2021-04-27 13:37         ` Paul E. McKenney
2021-04-27 17:50         ` Paul E. McKenney
2021-04-27 17:50           ` Paul E. McKenney
2021-04-27 21:09           ` Thomas Gleixner
2021-04-27 21:09             ` Thomas Gleixner
2021-04-28  1:48             ` Paul E. McKenney
2021-04-28  1:48               ` Paul E. McKenney
2021-04-28 10:14               ` Thomas Gleixner
2021-04-28 10:14                 ` Thomas Gleixner
2021-04-28 18:31                 ` Paul E. McKenney
2021-04-28 18:31                   ` Paul E. McKenney
2021-04-28 13:34             ` Thomas Gleixner
2021-04-28 13:34               ` Thomas Gleixner
2021-04-28 15:39               ` Peter Zijlstra
2021-04-28 15:39                 ` Peter Zijlstra
2021-04-28 17:00                 ` Thomas Gleixner
2021-04-28 17:00                   ` Thomas Gleixner
2021-04-29  7:38                   ` Feng Tang
2021-04-29  7:38                     ` Feng Tang
2021-04-28 18:31               ` Paul E. McKenney
2021-04-28 18:31                 ` Paul E. McKenney
2021-04-29  8:27                 ` Thomas Gleixner
2021-04-29  8:27                   ` Thomas Gleixner
2021-04-29 14:26                   ` Paul E. McKenney
2021-04-29 14:26                     ` Paul E. McKenney
2021-04-29 17:30                     ` Thomas Gleixner
2021-04-29 17:30                       ` Thomas Gleixner
2021-04-29 23:04                       ` Andi Kleen
2021-04-29 23:04                         ` Andi Kleen
2021-04-30  0:24                         ` Paul E. McKenney
2021-04-30  0:24                           ` Paul E. McKenney
2021-04-30  0:59                           ` Paul E. McKenney
2021-04-30  0:59                             ` Paul E. McKenney
2021-04-30  5:08                       ` Paul E. McKenney
2021-04-30  5:08                         ` Paul E. McKenney
2021-04-25 22:47 ` [PATCH v9 clocksource 6/6] clocksource: Reduce WATCHDOG_THRESHOLD Paul E. McKenney
2021-04-25 22:47 ` [PATCH v10 clocksource 7/7] " Paul E. McKenney

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