[Xen-devel] [PATCH] cpuidle: suspend/resume scheduler tick timer during cpu idle entry/exit V2

["Yu, Ke" <ke.yu@xxxxxxxxx>]

Hi Keir,

This attached is the version 2 of the patch. The major update is fixing the 
soft-lockup issue.

The root cause is: sched_tick_suspend will call __stop_timer and may raise 
TIMER_SOFTIRQ if the timer deadline is changed. In this case, the assumption of 
no softirq pending in acpi_processor_idle is broken, and later the hpet 
broadcast wakeup IPI will not be delivered to this CPU, since its softirq 
pending bit is set. Then the CPU will be sleeping until random external 
interrupt happen. To fix this issue, the sched_tick_suspend is moved before the 
softirq pending bit checking, to keep the assumption correct.

I also measure the performance by SPECJbb in dom0, no performance degradation 
observed.

Best Regards
Ke

Attachment: stop-sched-timer-idle-v2.patch
Description: stop-sched-timer-idle-v2.patch

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