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Date: Tue, 12 Nov 2013 09:25:49 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: "Wang, Xiaoming" <xiaoming.wang@intel.com>
Cc: Paul Turner <pjt@google.com>, Ingo Molnar <mingo@redhat.com>,
        LKML <linux-kernel@vger.kernel.org>,
        "Liu, Chuansheng" <chuansheng.liu@intel.com>,
        "Zhang, Dongxing" <dongxing.zhang@intel.com>
Subject: Re: [PATCH] [sched]: pick the NULL entity caused the panic.
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On Tue, Nov 12, 2013 at 06:38:24AM +0000, Wang, Xiaoming wrote:
> Dear Paul
> 	How about moving cfs_rq->nr_running into loop. What I worried is that cfs_rq->nr_running
> may zero because cfs_rq is coming from cfs_rq = group_cfs_rq(se) again. We haven't known the 
> reproduction exactly, panic happened only on random test and unstable. 

No; its just plain wrong. If this new condition can be true there's
something fundamentally messed up and we need to figure out what causes
that, not try and paper it over.