linux-kernel - [PATCH] intel_idle: Fix false positive RCU splats due to incorrect hardirqs state

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Message-Id: <20220723195932.1302575-1-longman@redhat.com>
Date:   Sat, 23 Jul 2022 15:59:32 -0400
From:   Waiman Long <longman@...hat.com>
To:     Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        Len Brown <lenb@...nel.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Waiman Long <longman@...hat.com>
Subject: [PATCH] intel_idle: Fix false positive RCU splats due to incorrect hardirqs state

Commit 32d4fd5751ea ("cpuidle,intel_idle: Fix CPUIDLE_FLAG_IRQ_ENABLE")
uses raw_local_irq_enable/local_irq_disable() around call to
__intel_idle() in intel_idle_irq().

With interrupt enabled, timer tick interrupt can happen and a
subsequently call to __do_softirq() may change the lockdep hardirqs state
of a debug kernel back to 'on'. This will result in a mismatch between
the cpu hardirqs state (off) and the lockdep hardirqs state (on) causing
a number of false positive "WARNING: suspicious RCU usage" splats.

Fix that by using local_irq_disable() to disable interrupt in
intel_idle_irq().

Fixes: 32d4fd5751ea ("cpuidle,intel_idle: Fix CPUIDLE_FLAG_IRQ_ENABLE")
Signed-off-by: Waiman Long <longman@...hat.com>
---
 drivers/idle/intel_idle.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
index f5c6802aa6c3..907700d1e78e 100644
--- a/drivers/idle/intel_idle.c
+++ b/drivers/idle/intel_idle.c
@@ -162,7 +162,13 @@ static __cpuidle int intel_idle_irq(struct cpuidle_device *dev,

 	raw_local_irq_enable();
 	ret = __intel_idle(dev, drv, index);
-	raw_local_irq_disable();
+
+	/*
+	 * The lockdep hardirqs state may be changed to 'on' with timer
+	 * tick interrupt followed by __do_softirq(). Use local_irq_disable()
+	 * to keep the hardirqs state correct.
+	 */
+	local_irq_disable();

 	return ret;
 }
-- 
2.31.1