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Date: Tue, 30 Sep 2014 14:20:59 -0400
From: Dave Jones <davej@redhat.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>,
        Linux Kernel <linux-kernel@vger.kernel.org>,
        Rik van Riel <riel@redhat.com>, Ingo Molnar <mingo@redhat.com>,
        Michel Lespinasse <walken@google.com>
Subject: Re: pipe/page fault oddness.
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On Tue, Sep 30, 2014 at 09:46:45AM -0700, Linus Torvalds wrote:
 > On Tue, Sep 30, 2014 at 9:40 AM, Dave Jones <davej@redhat.com> wrote:
 > >
 > > ah, echo 0 > tracing_on isn't enough, I had to 0 out set_ftrace_pid too.
 > > Never mind.  Subsequent traces all looking the same, minus the tracing
 > > junk though.
 > 
 > Yeah, looks like that copy_page_to_iter+0x3b3 is always there.
 > 
 > > Is there some way I can figure out what address it's faulting on ?
 > > I wonder if that might give some clues.
 > 
 > Could be useful. There's a trace_page_fault_kernel() entry that should
 > give it to you, along with error code.

Hm.

page_fault_kernel:    address=__per_cpu_end ip=copy_page_to_iter error_code=0x2

over and over..

	Dave