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Subject: Re: [next-20180517][ppc] watchdog: CPU 88 self-detected hard LOCKUP
 @ update_cfs_group+0x30/0x150
From: Abdul Haleem <abdhalee@linux.vnet.ibm.com>
To: Nicholas Piggin <npiggin@gmail.com>
Cc: sachinp <sachinp@linux.vnet.ibm.com>, Stephen Rothwell
 <sfr@canb.auug.org.au>, linux-kernel <linux-kernel@vger.kernel.org>,
 linux-next <linux-next@vger.kernel.org>, linuxppc-dev
 <linuxppc-dev@lists.ozlabs.org>
Date: Tue, 29 May 2018 18:39:40 +0530
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 <20180521165056.5f3dceeb@roar.ozlabs.ibm.com>
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On Mon, 2018-05-21 at 16:50 +1000, Nicholas Piggin wrote:
> Ah, it's POWER8.
> 
> I'm betting we have a bug with nohz timer offloading somewhere.
> 
> I *think* we may have seen similar on P9 as well, but that may be
> related to problems with stop states.
> 
> Can you reproduce it easily? I'm thinking maybe adding some
> tracepoints that track decrementer settings and interrupts, and
> nohz offload activity might show something up.

Yes, the problem is reproducible consistently on our CI setup and today
It triggered on 4.17.0-rc6 (mainline) too.

-- 
Regard's

Abdul Haleem
IBM Linux Technology Centre