Date: Thu, 4 Dec 2014 09:56:31 -0500
From: Dave Jones <davej@redhat.com>
To: Will Deacon <will.deacon@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
        "Kirill A. Shutemov" <kirill@shutemov.name>, Tejun Heo <tj@kernel.org>,
        Andy Lutomirski <luto@amacapital.net>, Don Zickus <dzickus@redhat.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Linux Kernel <linux-kernel@vger.kernel.org>,
        the arch/x86 maintainers <x86@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>
Subject: Re: frequent lockups in 3.18rc4
Message-ID: <20141204145631.GA22794@redhat.com>
Mail-Followup-To: Dave Jones <davej@redhat.com>,
	Will Deacon <will.deacon@arm.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	"Kirill A. Shutemov" <kirill@shutemov.name>,
	Tejun Heo <tj@kernel.org>, Andy Lutomirski <luto@amacapital.net>,
	Don Zickus <dzickus@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Linux Kernel <linux-kernel@vger.kernel.org>,
	the arch/x86 maintainers <x86@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>
References: <546D0530.8040800@mit.edu>
 <20141120152509.GA5412@redhat.com>
 <20141125122217.GA15280@arm.com>
 <20141201114854.GB18466@arm.com>
 <CA+55aFyhB5LBVadA5TfuX8+TrZZWTHwT-2NCYRLat8Fp6eBjgw@mail.gmail.com>
 <20141201171036.GH18466@arm.com>
 <CA+55aFwooh31=GMVUoriev+t92=roye_ck+czqr48M1sQ3UOMg@mail.gmail.com>
 <20141201182519.GA16749@node.dhcp.inet.fi>
 <CA+55aFz+ODi34J2n0kzXm+v++B7KW1e9NSFU=f-jgonPA1bNxg@mail.gmail.com>
 <20141204105103.GD14519@arm.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20141204105103.GD14519@arm.com>
User-Agent: Mutt/1.5.23 (2014-03-12)
Sender: linux-kernel-owner@vger.kernel.org

On Thu, Dec 04, 2014 at 10:51:03AM +0000, Will Deacon wrote:

 > and, as before, it has a weird child process that I can't backtrace:
 > 
 > trinity-c1      R  running task        0   861    811 0x00000000
 > Call trace:

When I get these, ftrace is a godsend.

cd /sys/kernel/debug/tracing/
echo 861 >> set_ftrace_pid
echo function_graph >> current_tracer
echo 1 >> tracing_on
wait a little while
cat trace > trace.txt

repeat last two steps if necessary

(assuming it's stuck in kernel space, which /proc/861/stack should
 be able to confirm. Usually when I see this problem, that just shows
 0xffffffffffffffff)

	Dave

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/