linux-kernel - Re: too many timer retries happen when do local timer swtich with broadcast timer

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Message-ID: <20130222103149.GC12140@e102568-lin.cambridge.arm.com>
Date:	Fri, 22 Feb 2013 10:31:49 +0000
From:	Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Santosh Shilimkar <santosh.shilimkar@...com>,
	Jason Liu <liu.h.jason@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: too many timer retries happen when do local timer swtich with
 broadcast timer

On Fri, Feb 22, 2013 at 10:24:00AM +0000, Thomas Gleixner wrote:
> On Fri, 22 Feb 2013, Santosh Shilimkar wrote:
> > BTW, Lorenzo off-list mentioned to me about warning in boot-up
> > which I missed while testing your patch. It will take bit more
> > time for me to look into it and hence thought of reporting it.
> > 
> > [    2.186126] ------------[ cut here ]------------
> > [    2.190979] WARNING: at kernel/time/tick-broadcast.c:501
> > tick_broadcast_oneshot_control+0x1c0/0x21c()
> 
> Which one is that? tick_broadcast_pending or tick_force_broadcast_mask ?

It is the tick_force_broadcast_mask and I think that's because on all
systems we are testing, the broadcast timer IRQ is a thundering herd,
all CPUs get out of idle at once and try to get out of broadcast mode
at more or less the same time.

Lorenzo

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