linux-kernel - [tip:timers/urgent] clocksource/exynos_mct: Clear interrupt when cpu is shut down

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Message-ID: <tip-bc7c36eedb0c7004aa06c2afc3c5385adada8fa3@git.kernel.org>
Date:   Tue, 17 Jan 2017 01:13:08 -0800
From:   tip-bot for Joonyoung Shim <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, hpa@...or.com,
        jy0922.shim@...sung.com, tglx@...utronix.de, mingo@...nel.org,
        sw0312.kim@...sung.com
Subject: [tip:timers/urgent] clocksource/exynos_mct: Clear interrupt when
 cpu is shut down

Commit-ID:  bc7c36eedb0c7004aa06c2afc3c5385adada8fa3
Gitweb:     http://git.kernel.org/tip/bc7c36eedb0c7004aa06c2afc3c5385adada8fa3
Author:     Joonyoung Shim <jy0922.shim@...sung.com>
AuthorDate: Tue, 17 Jan 2017 13:54:36 +0900
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Tue, 17 Jan 2017 10:08:38 +0100

clocksource/exynos_mct: Clear interrupt when cpu is shut down

When a CPU goes offline a potentially pending timer interrupt is not
cleared. When the CPU comes online again then the pending interrupt is
delivered before the per cpu clockevent device is initialized. As a
consequence the tick interrupt handler dereferences a NULL pointer.

[   51.251378] Unable to handle kernel NULL pointer dereference at virtual address 00000040
[   51.289348] task: ee942d00 task.stack: ee960000
[   51.293861] PC is at tick_periodic+0x38/0xb0
[   51.298102] LR is at tick_handle_periodic+0x1c/0x90

Clear the pending interrupt in the cpu dying path.

Fixes: 56a94f13919c ("clocksource: exynos_mct: Avoid blocking calls in the cpu hotplug notifier")
Reported-by: Seung-Woo Kim <sw0312.kim@...sung.com>
Signed-off-by: Joonyoung Shim <jy0922.shim@...sung.com>
Cc: linux-samsung-soc@...r.kernel.org
Cc: cw00.choi@...sung.com
Cc: daniel.lezcano@...aro.org
Cc: stable@...r.kernel.org
Cc: javier@....samsung.com
Cc: kgene@...nel.org
Cc: krzk@...nel.org
Cc: linux-arm-kernel@...ts.infradead.org
Link: http://lkml.kernel.org/r/1484628876-22065-1-git-send-email-jy0922.shim@samsung.com
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>

---
 drivers/clocksource/exynos_mct.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/clocksource/exynos_mct.c b/drivers/clocksource/exynos_mct.c
index 4da1dc2..670ff0f 100644
--- a/drivers/clocksource/exynos_mct.c
+++ b/drivers/clocksource/exynos_mct.c
@@ -495,6 +495,7 @@ static int exynos4_mct_dying_cpu(unsigned int cpu)
 	if (mct_int_type == MCT_INT_SPI) {
 		if (evt->irq != -1)
 			disable_irq_nosync(evt->irq);
+		exynos4_mct_write(0x1, mevt->base + MCT_L_INT_CSTAT_OFFSET);
 	} else {
 		disable_percpu_irq(mct_irqs[MCT_L0_IRQ]);
 	}