From: Peter Zijlstra <peterz@infradead.org>
To: Xi Wang <xii@google.com>
Cc: Ingo Molnar <mingo@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Josh Don <joshdon@google.com>,
linux-kernel@vger.kernel.org, Paul Turner <pjt@google.com>
Subject: Re: [PATCH v2 1/1] sched: watchdog: Touch kernel watchdog with sched count
Date: Wed, 21 Oct 2020 12:12:57 +0200 [thread overview]
Message-ID: <20201021101257.GC2628@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20201020205704.1741543-2-xii@google.com>
On Tue, Oct 20, 2020 at 01:57:04PM -0700, Xi Wang wrote:
> + if (watchdog_touch_with_sched) {
> + /* Trigger reschedule for the next round */
> + set_tsk_need_resched(current);
> + set_preempt_need_resched();
Blergh.. that's gross. This relies on this being in IRQ context and
either: PREEMPT=y *OR* this always being from userspace. Otherwise
there's no guarantee the return-from-interrupt will actually schedule.
> + /* sched_count increase in __schedule is taken as watchdog touched */
> + if (sched_get_count(smp_processor_id()) -
> + __this_cpu_read(watchdog_sched_prev)) {
> + __touch_watchdog();
> + __this_cpu_write(soft_watchdog_warn, false);
> + return HRTIMER_RESTART;
> + }
> + }
> +
> /* check for a softlockup
> * This is done by making sure a high priority task is
> * being scheduled. The task touches the watchdog to
> --
> 2.29.0.rc1.297.gfa9743e501-goog
>
next prev parent reply other threads:[~2020-10-21 10:13 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-20 20:57 [PATCH v2 0/1] Touch kernel watchdog with sched count Xi Wang
2020-10-20 20:57 ` [PATCH v2 1/1] sched: watchdog: " Xi Wang
2020-10-21 9:59 ` Peter Zijlstra
2020-10-21 10:12 ` Peter Zijlstra [this message]
2020-10-21 10:24 ` Peter Zijlstra
2020-10-21 11:11 ` Peter Zijlstra
2020-10-21 23:48 ` Xi Wang
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