From mboxrd@z Thu Jan 1 00:00:00 1970 From: gregkh@linuxfoundation.org (Greg Kroah-Hartman) Date: Tue, 24 Jan 2017 08:55:35 +0100 Subject: [PATCH 4.4 25/42] clocksource/exynos_mct: Clear interrupt when cpu is shut down In-Reply-To: <20170124075509.299412838@linuxfoundation.org> References: <20170124075509.299412838@linuxfoundation.org> Message-ID: <20170124075510.367397946@linuxfoundation.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Joonyoung Shim commit bc7c36eedb0c7004aa06c2afc3c5385adada8fa3 upstream. 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 Signed-off-by: Joonyoung Shim Cc: linux-samsung-soc at vger.kernel.org Cc: cw00.choi at samsung.com Cc: daniel.lezcano at linaro.org Cc: javier at osg.samsung.com Cc: kgene at kernel.org Cc: krzk at kernel.org Cc: linux-arm-kernel at lists.infradead.org Link: http://lkml.kernel.org/r/1484628876-22065-1-git-send-email-jy0922.shim at samsung.com Signed-off-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman --- drivers/clocksource/exynos_mct.c | 1 + 1 file changed, 1 insertion(+) --- a/drivers/clocksource/exynos_mct.c +++ b/drivers/clocksource/exynos_mct.c @@ -482,6 +482,7 @@ static void exynos4_local_timer_stop(str 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]); }