From 9bf11ecce5a2758e5a097c2f3a13d08552d0d6f9 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Thu, 15 Dec 2016 12:01:05 +0100 Subject: [PATCH 1/2] clocksource/dummy_timer: Move hotplug callback after the real timers When the dummy timer callback is invoked before the real timer callbacks, then it tries to install that timer for the starting CPU. If the platform does not have a broadcast timer installed the installation fails with a kernel crash. The crash happens due to a unconditional deference of the non available broadcast device. This needs to be fixed in the timer core code. But even when this is fixed in the core code then installing the dummy timer before the real timers is a pointless exercise. Move it to the end of the callback list. Fixes: 00c1d17aab51 ("clocksource/dummy_timer: Convert to hotplug state machine") Reported-and-tested-by: Mason Signed-off-by: Thomas Gleixner Cc: Mark Rutland Cc: Anna-Maria Gleixner Cc: Richard Cochran Cc: Sebastian Andrzej Siewior Cc: Daniel Lezcano Cc: Peter Zijlstra , Cc: Sebastian Frias Cc: Thibaud Cornic Cc: Robin Murphy Link: http://lkml.kernel.org/r/1147ef90-7877-e4d2-bb2b-5c4fa8d3144b@free.fr --- include/linux/cpuhotplug.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h index 22acee76cf4c..2ab7bf53d529 100644 --- a/include/linux/cpuhotplug.h +++ b/include/linux/cpuhotplug.h @@ -101,7 +101,6 @@ enum cpuhp_state { CPUHP_AP_ARM_L2X0_STARTING, CPUHP_AP_ARM_ARCH_TIMER_STARTING, CPUHP_AP_ARM_GLOBAL_TIMER_STARTING, - CPUHP_AP_DUMMY_TIMER_STARTING, CPUHP_AP_JCORE_TIMER_STARTING, CPUHP_AP_EXYNOS4_MCT_TIMER_STARTING, CPUHP_AP_ARM_TWD_STARTING, @@ -115,6 +114,8 @@ enum cpuhp_state { CPUHP_AP_KVM_ARM_VGIC_INIT_STARTING, CPUHP_AP_KVM_ARM_VGIC_STARTING, CPUHP_AP_KVM_ARM_TIMER_STARTING, + /* Must be the last timer callback */ + CPUHP_AP_DUMMY_TIMER_STARTING, CPUHP_AP_ARM_XEN_STARTING, CPUHP_AP_ARM_CORESIGHT_STARTING, CPUHP_AP_ARM_CORESIGHT4_STARTING, From 512f09801b356c54baef62543e51169f03b2e642 Mon Sep 17 00:00:00 2001 From: Boris Ostrovsky Date: Thu, 15 Dec 2016 10:00:57 -0500 Subject: [PATCH 2/2] cpu/hotplug: Clarify description of __cpuhp_setup_state() return value When invoked with CPUHP_AP_ONLINE_DYN state __cpuhp_setup_state() is expected to return positive value which is the hotplug state that the routine assigns. Signed-off-by: Boris Ostrovsky Cc: linux-pm@vger.kernel.org Cc: viresh.kumar@linaro.org Cc: bigeasy@linutronix.de Cc: rjw@rjwysocki.net Cc: xen-devel@lists.xenproject.org Link: http://lkml.kernel.org/r/1481814058-4799-2-git-send-email-boris.ostrovsky@oracle.com Signed-off-by: Thomas Gleixner --- kernel/cpu.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/kernel/cpu.c b/kernel/cpu.c index 217fd2e7f435..5339aca811d2 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -1586,7 +1586,11 @@ EXPORT_SYMBOL_GPL(__cpuhp_state_add_instance); * @startup: startup callback function * @teardown: teardown callback function * - * Returns 0 if successful, otherwise a proper error code + * Returns: + * On success: + * Positive state number if @state is CPUHP_AP_ONLINE_DYN + * 0 for all other states + * On failure: proper (negative) error code */ int __cpuhp_setup_state(enum cpuhp_state state, const char *name, bool invoke,