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

Andi Kleen
2010-01-13T23:50:10Z

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@sisk.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@firstfloor.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@linux.intel.com -- Speaking for myself only.