linux-kernel - Re: pipe/page fault oddness.

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Date:	Tue, 30 Sep 2014 14:20:59 -0400
From:	Dave Jones <davej@...hat.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Al Viro <viro@...iv.linux.org.uk>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Rik van Riel <riel@...hat.com>,
	Ingo Molnar <mingo@...hat.com>,
	Michel Lespinasse <walken@...gle.com>
Subject: Re: pipe/page fault oddness.

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@...hat.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


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