From: Joonyoung Shim jy0922.shim@samsung.com
[ Upstream commit bc7c36eedb0c7004aa06c2afc3c5385adada8fa3 ]
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@samsung.com Signed-off-by: Joonyoung Shim jy0922.shim@samsung.com Cc: linux-samsung-soc@vger.kernel.org Cc: cw00.choi@samsung.com Cc: daniel.lezcano@linaro.org Cc: stable@vger.kernel.org Cc: javier@osg.samsung.com Cc: kgene@kernel.org Cc: krzk@kernel.org Cc: linux-arm-kernel@lists.infradead.org Link: http://lkml.kernel.org/r/1484628876-22065-1-git-send-email-jy0922.shim@samsu... Signed-off-by: Thomas Gleixner tglx@linutronix.de Signed-off-by: Sasha Levin sashal@kernel.org --- 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 c844616028d2..714f9a767b17 100644 --- a/drivers/clocksource/exynos_mct.c +++ b/drivers/clocksource/exynos_mct.c @@ -487,6 +487,7 @@ static void exynos4_local_timer_stop(struct clock_event_device *evt) 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]); }