linux-kernel - [PATCH] clockevents/drivers/cs5535: improve resilience to spurious interrupts

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Message-Id: <20171019211651.039346004D@linux.fjfi.cvut.cz>
Date:   Thu, 19 Oct 2017 22:57:02 +0200
From:   David Kozub <zub@...ux.fjfi.cvut.cz>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH] clockevents/drivers/cs5535: improve resilience to spurious
 interrupts

This solves a BUG on ALIX 2c3 where mfgpt_tick is called before
clockevents_config_and_register returns. This caused mfgpt_tick to call a
null function pointer.

Thanks to Daniel Lezcano and Thomas Gleixner for helping me analyze this
and suggesting a solution.

Suggested-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: David Kozub <zub@...ux.fjfi.cvut.cz>
---
 drivers/clocksource/cs5535-clockevt.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/clocksource/cs5535-clockevt.c b/drivers/clocksource/cs5535-clockevt.c
index a1df588343f2..56100506b933 100644
--- a/drivers/clocksource/cs5535-clockevt.c
+++ b/drivers/clocksource/cs5535-clockevt.c
@@ -117,7 +117,8 @@ static irqreturn_t mfgpt_tick(int irq, void *dev_id)
 	/* Turn off the clock (and clear the event) */
 	disable_timer(cs5535_event_clock);
 
-	if (clockevent_state_shutdown(&cs5535_clockevent))
+	if (clockevent_state_detached(&cs5535_clockevent) ||
+			clockevent_state_shutdown(&cs5535_clockevent))
 		return IRQ_HANDLED;
 
 	/* Clear the counter */
-- 
2.14.2