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

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Message-ID: <alpine.DEB.2.11.1507031612410.3916@nanos>
Date:	Fri, 3 Jul 2015 16:17:13 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Wolfram Sang <wsa@...-dreams.de>
cc:	Simon Horman <horms@...ge.net.au>,
	Kevin Hilman <khilman@...nel.org>,
	Tyler Baker <tyler.baker@...aro.org>,
	Borislav Petkov <bp@...en8.de>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	Magnus Damm <magnus.damm@...il.com>, linux-sh@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: Possible regression due to "tick: broadcast: Prevent livelock
 from event handler"

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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