From: "Paul E. McKenney" <paulmck@kernel.org>
To: Rik van Riel <riel@fb.com>
Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com,
John Stultz <john.stultz@linaro.org>,
Thomas Gleixner <tglx@linutronix.de>,
Stephen Boyd <sboyd@kernel.org>, Jonathan Corbet <corbet@lwn.net>,
Mark Rutland <Mark.Rutland@arm.com>,
Marc Zyngier <maz@kernel.org>
Subject: Re: [PATCH RFC clocksource 2/5] clocksource: Retry clock read if long delays detected
Date: Wed, 6 Jan 2021 11:53:21 -0800 [thread overview]
Message-ID: <20210106195321.GC2743@paulmck-ThinkPad-P72> (raw)
In-Reply-To: <edbe9ac5fc3f76601f752ce2c5a8052dc05fd4f6.camel@fb.com>
On Wed, Jan 06, 2021 at 11:28:00AM -0500, Rik van Riel wrote:
> On Tue, 2021-01-05 at 16:41 -0800, paulmck@kernel.org wrote:
> >
> > @@ -203,7 +204,6 @@ static void
> > clocksource_watchdog_inject_delay(void)
> > injectfail = inject_delay_run;
> > if (!(++injectfail / inject_delay_run % inject_delay_freq)) {
> > printk("%s(): Injecting delay.\n", __func__);
> > - injectfail = 0;
> > for (i = 0; i < 2 * WATCHDOG_THRESHOLD / NSEC_PER_MSEC;
> > i++)
> > udelay(1000);
>
> Wait, patch 1 just added that line?
>
> Should patch 1 not add it and this
> patch go without
> this removal? :)
Good catch, will fix. ;-)
> + wdagain_nsec = clocksource_cyc2ns(delta, watchdog-
> >mult, watchdog->shift);
> + if (wdagain_nsec < 0 || wdagain_nsec >
> WATCHDOG_MAX_SKEW) {
> + wderr_nsec = wdagain_nsec;
> + if (nretries++ < max_read_retries)
> + goto retry;
> + }
>
> Given that clocksource_cyc2ns uses unsigned multiplication
> followed by a right shift, do we need to test for <0?
I am worried about the possibility of the "shift" argument to
clocksource_cyc2ns() being zero. For example, unless I am missing
something, clocksource_tsc has a zero .shift field.
Thanx, Paul
next prev parent reply other threads:[~2021-01-06 19:54 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 [this message]
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
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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