From: Frederic Weisbecker <frederic@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Frederic Weisbecker <frederic@kernel.org>,
"Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
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 4/4] ACPI: processor: Fix missing need_resched() check after rcu_idle_enter()
Date: Mon, 4 Jan 2021 16:20:58 +0100 [thread overview]
Message-ID: <20210104152058.36642-5-frederic@kernel.org> (raw)
In-Reply-To: <20210104152058.36642-1-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 within acpi_idle_enter_bm() the call to rcu_idle_enter()
is already beyond the last generic need_resched() check. The cpu idle
implementation happens to be ok because it ends up calling
mwait_idle_with_hints() or acpi_safe_halt() which both perform their own
need_resched() checks. But the suspend to idle implementation doesn't so
it may suspend 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>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Fixes: 1fecfdbb7acc (ACPI: processor: Take over RCU-idle for C3-BM idle)
Cc: stable@vger.kernel.org
Cc: Len Brown <lenb@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar<mingo@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
---
drivers/acpi/processor_idle.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index d93e400940a3..c4939c49d972 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -604,8 +604,14 @@ static int acpi_idle_enter_bm(struct cpuidle_driver *drv,
}
rcu_idle_enter();
-
- acpi_idle_do_entry(cx);
+ /*
+ * Last need_resched() check must come after rcu_idle_enter()
+ * which may wake up RCU internal tasks. mwait_idle_with_hints()
+ * and acpi_safe_halt() have their own checks but s2idle
+ * implementation doesn't.
+ */
+ if (!need_resched())
+ acpi_idle_do_entry(cx);
rcu_idle_exit();
--
2.25.1
next prev parent reply other threads:[~2021-01-04 15:22 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
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 1/4] sched/idle: Fix missing need_resched() check after rcu_idle_enter() Frederic Weisbecker
2021-01-05 9:55 ` Peter Zijlstra
2021-01-05 12:57 ` Frederic Weisbecker
2021-01-06 10:33 ` Peter Zijlstra
2021-01-05 23:25 ` Paul E. McKenney
2021-01-05 23:47 ` Frederic Weisbecker
2021-01-04 15:20 ` [PATCH 2/4] cpuidle: " Frederic Weisbecker
2021-01-04 15:20 ` [PATCH 3/4] ARM: imx6q: " Frederic Weisbecker
2021-01-04 15:57 ` Fabio Estevam
2021-01-04 15:20 ` Frederic Weisbecker [this message]
-- strict thread matches above, loose matches on Subject: below --
2020-12-22 1:37 [PATCH 0/4] sched/idle: Fix missing need_resched() checks " Frederic Weisbecker
2020-12-22 1:37 ` [PATCH 4/4] ACPI: processor: Fix missing need_resched() check " Frederic Weisbecker
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