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authorThomas Gleixner <tglx@linutronix.de>2014-02-11 14:35:40 +0100
committerThomas Gleixner <tglx@linutronix.de>2014-02-13 21:55:54 +0100
commitdd5fd9b91a77b4c9c28b7ef9c181b1a875820d0a (patch)
tree3f55bbcb0828da3ae3ca10ee04ec1eab541e200a /kernel
parentad037c1f4ae6f9258f27fddb679ceb703ff07a88 (diff)
downloadlinux-dd5fd9b91a77b4c9c28b7ef9c181b1a875820d0a.tar.gz
tick: Clear broadcast pending bit when switching to oneshot
AMD systems which use the C1E workaround in the amd_e400_idle routine trigger the WARN_ON_ONCE in the broadcast code when onlining a CPU. The reason is that the idle routine of those AMD systems switches the cpu into forced broadcast mode early on before the newly brought up CPU can switch over to high resolution / NOHZ mode. The timer related CPU1 bringup looks like this: clockevent_register_device(local_apic); tick_setup(local_apic); ... idle() tick_broadcast_on_off(FORCE); tick_broadcast_oneshot_control(ENTER) cpumask_set(cpu, broadcast_oneshot_mask); halt(); Now the broadcast interrupt on CPU0 sets CPU1 in the broadcast_pending_mask and wakes CPU1. So CPU1 continues: local_apic_timer_interrupt() tick_handle_periodic(); softirq() tick_init_highres(); cpumask_clr(cpu, broadcast_oneshot_mask); tick_broadcast_oneshot_control(ENTER) WARN_ON(cpumask_test(cpu, broadcast_pending_mask); So while we remove CPU1 from the broadcast_oneshot_mask when we switch over to highres mode, we do not clear the pending bit, which then triggers the warning when we go back to idle. The reason why this is only visible on C1E affected AMD systems is that the other machines enter the deep sleep states via acpi_idle/intel_idle and exit the broadcast mode before executing the remote triggered local_apic_timer_interrupt. So the pending bit is already cleared when the switch over to highres mode is clearing the oneshot mask. The solution is simple: Clear the pending bit together with the mask bit when we switch over to highres mode. Stanislaw came up independently with the same patch by enforcing the C1E workaround and debugging the fallout. I picked mine, because mine has a changelog :) Reported-by: poma <pomidorabelisima@gmail.com> Debugged-by: Stanislaw Gruszka <sgruszka@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Olaf Hering <olaf@aepfle.de> Cc: Dave Jones <davej@redhat.com> Cc: Justin M. Forbes <jforbes@redhat.com> Cc: Josh Boyer <jwboyer@redhat.com> Link: http://lkml.kernel.org/r/alpine.DEB.2.02.1402111434180.21991@ionos.tec.linutronix.de Cc: stable@vger.kernel.org # 3.10+ Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/time/tick-broadcast.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index 43780ab5e27..98977a57ac7 100644
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -756,6 +756,7 @@ out:
static void tick_broadcast_clear_oneshot(int cpu)
{
cpumask_clear_cpu(cpu, tick_broadcast_oneshot_mask);
+ cpumask_clear_cpu(cpu, tick_broadcast_pending_mask);
}
static void tick_broadcast_init_next_event(struct cpumask *mask,