From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
To: Frederic Weisbecker <frederic@kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>,
Fabio Estevam <festevam@gmail.com>,
stable@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>,
"Paul E . McKenney" <paulmck@kernel.org>,
Len Brown <lenb@kernel.org>,
Pengutronix Kernel Team <kernel@pengutronix.de>,
NXP Linux Team <linux-imx@nxp.com>,
Daniel Lezcano <daniel.lezcano@linaro.org>,
Shawn Guo <shawnguo@kernel.org>,
Sascha Hauer <s.hauer@pengutronix.de>,
Linux PM <linux-pm@vger.kernel.org>
Subject: Re: [PATCH 0/4] sched/idle: Fix missing need_resched() checks after rcu_idle_enter()
Date: Tue, 22 Dec 2020 17:19:51 +0100 [thread overview]
Message-ID: <4de33f1a-890b-4d29-20e8-a1163b9c1bf7@intel.com> (raw)
In-Reply-To: <20201222013712.15056-1-frederic@kernel.org>
On 12/22/2020 2:37 AM, Frederic Weisbecker wrote:
> With Paul, we've been thinking that the idle loop wasn't twisted enough
> yet to deserve 2020.
>
> rcutorture, after some recent parameter changes, has been complaining
> about a hung task.
>
> It appears that rcu_idle_enter() may wake up a NOCB kthread but this
> happens after the last generic need_resched() check. Some cpuidle drivers
> fix it by chance but many others don't.
>
> Here is a proposed bunch of fixes. I will need to also fix the
> rcu_user_enter() case, likely using irq_work, since nohz_full requires
> irq work to support self IPI.
>
> Also more generally, this raise the question of local task wake_up()
> under disabled interrupts. When a wake up occurs in a preempt disabled
> section, it gets handled by the outer preempt_enable() call. There is no
> similar mechanism when a wake up occurs with interrupts disabled. I guess
> it is assumed to be handled, at worst, in the next tick. But a local irq
> work would provide instant preemption once IRQs are re-enabled. Of course
> this would only make sense in CONFIG_PREEMPTION, and when the tick is
> disabled...
>
> git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks.git
> sched/idle
>
> HEAD: f2fa6e4a070c1535b9edc9ee097167fd2b15d235
>
> Thanks,
> Frederic
> ---
>
> Frederic Weisbecker (4):
> sched/idle: Fix missing need_resched() check after rcu_idle_enter()
> cpuidle: Fix missing need_resched() check after rcu_idle_enter()
> ARM: imx6q: Fix missing need_resched() check after rcu_idle_enter()
> ACPI: processor: Fix missing need_resched() check after rcu_idle_enter()
>
>
> arch/arm/mach-imx/cpuidle-imx6q.c | 7 ++++++-
> drivers/acpi/processor_idle.c | 10 ++++++++--
> drivers/cpuidle/cpuidle.c | 33 +++++++++++++++++++++++++--------
> kernel/sched/idle.c | 18 ++++++++++++------
> 4 files changed, 51 insertions(+), 17 deletions(-)
Please feel free to add
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
to all patches in the series.
Thanks!
next prev parent reply other threads:[~2020-12-22 16:21 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-22 1:37 [PATCH 0/4] sched/idle: Fix missing need_resched() checks after rcu_idle_enter() Frederic Weisbecker
2020-12-22 1:37 ` [PATCH 1/4] sched/idle: Fix missing need_resched() check " Frederic Weisbecker
2020-12-22 4:20 ` Paul E. McKenney
2020-12-22 1:37 ` [PATCH 2/4] cpuidle: " Frederic Weisbecker
2021-01-05 17:25 ` Dmitry Osipenko
2021-01-05 18:10 ` Dmitry Osipenko
2021-01-05 19:17 ` Paul E. McKenney
2020-12-22 1:37 ` [PATCH 3/4] ARM: imx6q: " Frederic Weisbecker
2020-12-22 1:37 ` [PATCH 4/4] ACPI: processor: " Frederic Weisbecker
2020-12-22 16:19 ` Rafael J. Wysocki [this message]
2021-01-01 16:05 ` [PATCH 0/4] sched/idle: Fix missing need_resched() checks " Paul E. McKenney
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