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To: Andrea Arcangeli <andrea@suse.de>
Cc: "Magnus Naeslund(f)" <mag@fbab.net>,
        linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: Alpha compile problem solved by Andrea (pte_alloc)
In-Reply-To: <052901c0ceca$e6a543c0$020a0a0a@totalmef> <20010427155246.O16020@athlon.random> <m1k843qoc1.fsf@frodo.biederman.org> <20010430014653.C923@athlon.random>
From: ebiederm@xmission.com (Eric W. Biederman)
Date: 29 Apr 2001 21:55:06 -0600
In-Reply-To: Andrea Arcangeli's message of "Mon, 30 Apr 2001 01:46:53 +0200"
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Andrea Arcangeli <andrea@suse.de> writes:

> On Sun, Apr 29, 2001 at 05:27:10PM -0600, Eric W. Biederman wrote:
> > 
> > Do you know if anyone has fixed the lazy vmalloc code?  I know of
> > as of early 2.4 it was broken on alpha.  At the time I noticed it I didn't
> > have time to persue it, but before I forget to even put in a bug
> > report I thought I'd ask if you know anything about it?
> 
> On alpha it's racy if you set CONFIG_ALPHA_LARGE_VMALLOC y (so don't do
> that as you don't need it). As long as you use only 1 entry of the pgd
> for the whole vmalloc space (CONFIG_ALPHA_LARGE_VMALLOC n) alpha is
> safe.

Hmm. I was having problems reproducible with
CONFIG_ALPHA_LARGE_VMALLOC n.

Enabling the large vmalloc was my work around, because the large
vmalloc whet back to the prelazy allocation code.

I was getting repeatable problems inside of an mtd driver.  The
problem I had was entries failed to propagate across different tasks.
I think it was something like the first pgd was lazily allocated and
not propagated.   

I don't have a SRM on my 264 alpha so alpha (for reference on which
code paths were followed.

> 
> OTOH x86 is racy and there's no workaround available at the moment.

GH

Well racy is easier to work with than just plain non-functional. 

Eric

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