linux-kernel - Re: [BUG] sched: tip/master show panic while booting/rebooting

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Message-ID: <20140219115747.GJ15586@twins.programming.kicks-ass.net>
Date:	Wed, 19 Feb 2014 12:57:47 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Michael wang <wangyun@...ux.vnet.ibm.com>
Cc:	paulus@...ba.org, Ingo Molnar <mingo@...hat.com>,
	acme@...stprotocols.net, Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [BUG] sched: tip/master show panic while booting/rebooting

On Wed, Feb 19, 2014 at 11:12:11AM +0800, Michael wang wrote:
> On 02/18/2014 07:22 PM, Peter Zijlstra wrote:
> > On Tue, Feb 18, 2014 at 01:12:03PM +0800, Michael wang wrote:
> >> Hi, Folks
> >>
> >> Got below panic while testing tip/master on x86 box, it randomly
> >> occur while booting or rebooting, any ideas?
> > 
> > The obvious pick would be the relocation of the idle_balance call, but
> > I'm not sure how that'll end up stalling.
> 
> I've review the code again, seems like it was caused by the same issue
> we discussed (RT/DL enqueued issue), I found that idle_balance() will
> return 1 in such cases:
> 
>         /*
>          * While browsing the domains, we released the rq lock.
>          * A task could have be enqueued in the meantime
>          */
>         if (this_rq->nr_running && !pulled_task)
>                 return 1;
> 
> And if no more fair task to be pulled, we will do balance again and
> again in pick_next_task_fair() until panic in NMI...
> 
> The solution we discussed could solve the problem I suppose, it was
> already in progress, correct?
> 
> Please let me know if there are any thing I could help with ;-)

Great, thanks!

Right, I'm waiting for Ingo to appear and commit some patches into tip.
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