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Message-Id: <1219314010.7827.4.camel@localhost>
Date: Thu, 21 Aug 2008 20:20:10 +1000
From: Michael Ellerman <michael@...erman.id.au>
To: Arnd Bergmann <arnd@...db.de>
Cc: cbe-oss-dev@...abs.org, Robert Richter <robert.richter@....com>,
linux-kernel <linux-kernel@...r.kernel.org>,
linuxppc-dev@...abs.org, oprofile-list@...ts.sourceforge.net,
cel <cel@...ux.vnet.ibm.com>
Subject: Re: [Cbe-oss-dev] powerpc/cell/oprofile: fix mutex locking for
spu-oprofile
On Thu, 2008-08-21 at 10:14 +0200, Arnd Bergmann wrote:
> On Thursday 21 August 2008, Paul Mackerras wrote:
> > Arnd Bergmann writes:
> >
> > > Paul, any chance we can still get this into 2.6.27?
> >
> > Possibly. We'll need a really good explanation for Linus as to why
> > this is needed (what regression or serious bug this fixes) and why it
> > is late. Can you send me something explaining that?
>
> The patch does not fix a regression, the spu-oprofile code basically never
> worked. With the current code in Linux, samples in the profile buffer
> can get corrupted because reader and writer to that buffer use different
> locks for accessing it.
Actually for me it worked[1] a reasonable amount of the time, enough to
be useful. So the spu-oprofile code has always been broken in this way,
but it's not always fatal. So the patch doesn't fix a regression, but it
fixes a serious user-visible bug, which makes it legit rc4 material
IMHO.
[1] that was late last year, so possibly a kernel or two ago.
cheers
--
Michael Ellerman
OzLabs, IBM Australia Development Lab
wwweb: http://michael.ellerman.id.au
phone: +61 2 6212 1183 (tie line 70 21183)
We do not inherit the earth from our ancestors,
we borrow it from our children. - S.M.A.R.T Person
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