linux-kernel - Re: [Bug #15041] Pagemap endless read loop with LTP

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Message-ID: <20100113235010.GF24818@basil.fritz.box>
Date:	Thu, 14 Jan 2010 00:50:10 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Américo Wang <xiyou.wangcong@...il.com>,
	Andi Kleen <andi@...stfloor.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Kernel Testers List <kernel-testers@...r.kernel.org>
Subject: Re: [Bug #15041] Pagemap endless read loop with LTP

On Wed, Jan 13, 2010 at 10:57:34PM +0100, Rafael J. Wysocki wrote:
> On Wednesday 13 January 2010, Américo Wang wrote:
> > On Mon, Jan 11, 2010 at 6:32 AM, Rafael J. Wysocki <rjw@...k.pl> wrote:
> > > This message has been generated automatically as a part of a report
> > > of recent regressions.
> > >
> > > The following bug entry is on the current list of known regressions
> > > from 2.6.32.  Please verify if it still should be listed and let me know
> > > (either way).
> > >
> > >
> > > Bug-Entry       : http://bugzilla.kernel.org/show_bug.cgi?id=15041
> > > Subject         : Pagemap endless read loop with LTP
> > > Submitter       : Andi Kleen <andi@...stfloor.org>
> > > Date            : 2010-01-10 2:09 (1 days old)
> > > References      : http://marc.info/?l=linux-kernel&m=126308941423848&w=4
> > >
> > 
> > According to Andi's later reply, it shoud not be an endless loop,
> > it just takes a rather long time.
> 
> Andi?

It'll try to read 47 bits worth of 0s on 64bit x86-64. 

I haven't tried to wait until that finishes, but I estimate a few months of 
CPU time at least.

The interface is just misdesigned, but I guess we cannot do
anything about that for now. LTP will just need to do a workaround.

This unfortunately breaks older LTP versions.

-Andi
-- 
ak@...ux.intel.com -- Speaking for myself only.
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