Xen devel - Mar 2009 - [PATCH] cpuidle: suspend/resume scheduler tick timer during cpu idle entry/exit V2

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



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