Re: Possible regression due to "tick: broadcast: Prevent livelock from event handler"

From: Thomas Gleixner
Date: Fri Jul 03 2015 - 10:17:42 EST


On Fri, 3 Jul 2015, Wolfram Sang wrote:

>
> > So with high res timers it boots. Can you please provide the output of
> > /proc/timer_list for that case?

> Tick Device: mode: 1
> Per CPU device: 0
> Clock Event Device: e0180000.timer
> max_delta_ns: 131071523464982
> min_delta_ns: 61035
> mult: 70369
> shift: 31
> mode: 3
> next_event: 40760000000 nsecs
> set_next_event: em_sti_clock_event_next
> set_mode: em_sti_clock_event_mode
> event_handler: hrtimer_interrupt
> retries: 0

So this is a single core machine and uses the em_sti timer w/o the
broadcast nonsense. In Simons case it looks like em_sti is used as
broadcast device.

Though the issues you see in the highres=n case might be the same as
the ones Simon is observing.

So in that nohz=y highres=n case, does adding idle=poll on the command
line fix the issue?

Thanks,

tglx
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