From: Frederic Weisbecker <frederic@kernel.org>
To: LKML <linux-kernel@vger.kernel.org>
Cc: Frederic Weisbecker <frederic@kernel.org>,
"Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
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>
Subject: [PATCH 3/4] ARM: imx6q: Fix missing need_resched() check after rcu_idle_enter()
Date: Tue, 22 Dec 2020 02:37:11 +0100 [thread overview]
Message-ID: <20201222013712.15056-4-frederic@kernel.org> (raw)
In-Reply-To: <20201222013712.15056-1-frederic@kernel.org>
Entering RCU idle mode may cause a deferred wake up of an RCU NOCB_GP
kthread (rcuog) to be serviced.
Usually a wake up happening while running the idle task is spotted in
one of the need_resched() checks carefully placed within the idle loop
that can break to the scheduler.
Unfortunately imx6q_enter_wait() is beyond the last generic
need_resched() check and it performs a wfi right away after the call to
rcu_idle_enter(). We may halt the CPU with a resched request unhandled,
leaving the task hanging.
Fix this with performing a last minute need_resched() check after
calling rcu_idle_enter().
Reported-by: Paul E. McKenney <paulmck@kernel.org>
Fixes: 1a67b9263e06 (ARM: imx6q: Fixup RCU usage for cpuidle)
Cc: stable@vger.kernel.org
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Pengutronix Kernel Team <kernel@pengutronix.de>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: NXP Linux Team <linux-imx@nxp.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
---
arch/arm/mach-imx/cpuidle-imx6q.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/arch/arm/mach-imx/cpuidle-imx6q.c b/arch/arm/mach-imx/cpuidle-imx6q.c
index 094337dc1bc7..31a60d257d3d 100644
--- a/arch/arm/mach-imx/cpuidle-imx6q.c
+++ b/arch/arm/mach-imx/cpuidle-imx6q.c
@@ -25,7 +25,12 @@ static int imx6q_enter_wait(struct cpuidle_device *dev,
raw_spin_unlock(&cpuidle_lock);
rcu_idle_enter();
- cpu_do_idle();
+ /*
+ * Last need_resched() check must come after rcu_idle_enter()
+ * which may wake up RCU internal tasks.
+ */
+ if (!need_resched())
+ cpu_do_idle();
rcu_idle_exit();
raw_spin_lock(&cpuidle_lock);
--
2.25.1
next prev parent reply other threads:[~2020-12-22 1:38 UTC|newest]
Thread overview: 13+ 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 ` Frederic Weisbecker [this message]
2020-12-22 1:37 ` [PATCH 4/4] ACPI: processor: " Frederic Weisbecker
2020-12-22 16:19 ` [PATCH 0/4] sched/idle: Fix missing need_resched() checks " Rafael J. Wysocki
2021-01-01 16:05 ` Paul E. McKenney
2021-01-04 15:20 [PATCH 0/4] sched/idle: Fix missing need_resched() checks after rcu_idle_enter() v2 Frederic Weisbecker
2021-01-04 15:20 ` [PATCH 3/4] ARM: imx6q: Fix missing need_resched() check after rcu_idle_enter() Frederic Weisbecker
2021-01-04 15:57 ` Fabio Estevam
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