Date: Fri, 12 Dec 2014 14:23:09 -0500
From: Dave Jones <davej@redhat.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Chris Mason <clm@fb.com>, Mike Galbraith <umgwanakikbuti@gmail.com>,
        Ingo Molnar <mingo@kernel.org>, Peter Zijlstra <peterz@infradead.org>,
        =?iso-8859-1?Q?D=E2niel?= Fraga <fragabr@gmail.com>,
        Sasha Levin <sasha.levin@oracle.com>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: frequent lockups in 3.18rc4
Message-ID: <20141212192309.GA10523@redhat.com>
Mail-Followup-To: Dave Jones <davej@redhat.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Chris Mason <clm@fb.com>, Mike Galbraith <umgwanakikbuti@gmail.com>,
	Ingo Molnar <mingo@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	=?iso-8859-1?Q?D=E2niel?= Fraga <fragabr@gmail.com>,
	Sasha Levin <sasha.levin@oracle.com>,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
References: <20141203184111.GA32005@redhat.com>
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 <CA+55aFxVeti8pU=Y_w54oGb8syGduOySAp-ag+KsCom-c12e-Q@mail.gmail.com>
 <1417806247.4845.1@mail.thefacebook.com>
 <CA+55aFz3iUyV9=_rVUdO0WPoOyOKOYkcHCxb3p=2fgSHtCTNgw@mail.gmail.com>
 <20141211145408.GB16800@redhat.com>
 <CA+55aFy1_w1NrkeopMXsxGftO5F03JzKgn-8uTQRnEAXuoiXgg@mail.gmail.com>
 <20141212185454.GB4716@redhat.com>
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On Fri, Dec 12, 2014 at 11:14:06AM -0800, Linus Torvalds wrote:
 > On Fri, Dec 12, 2014 at 10:54 AM, Dave Jones <davej@redhat.com> wrote:
 > >
 > > Something that's still making me wonder if it's some kind of hardware
 > > problem is the non-deterministic nature of this bug.
 > 
 > I'd expect it to be a race condition, though. Which can easily cause
 > these kinds of issues, and the timing will be pretty random even if
 > the load is very regular.
 > 
 > I'm also not sure if the bug ever happens with preemption disabled.

After tomorrow, I'm not going to be in front of this machine until
Wednesday, so I'll leave a no-preempt build running for the duration.
Hopefully that will give us some clues.  I might be able to log into
it while travelling, so I'll provide updates where possible as long
as it doesn't wedge solid.

	Dave

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