linux-kernel - Re: [RFC/PATCH] mm: Pass virtual address to [__]p{te,ud,md}_free

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Date:	Tue, 28 Jul 2009 09:25:29 +0900
From:	Paul Mundt <lethal@...ux-sh.org>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Nick Piggin <npiggin@...e.de>,
	Linux Memory Management <linux-mm@...ck.org>,
	Linux-Arch <linux-arch@...r.kernel.org>,
	linux-kernel@...r.kernel.org, linuxppc-dev@...abs.org,
	Hugh Dickins <hugh@...cali.co.uk>, ralf <ralf@...ux-mips.org>
Subject: Re: [RFC/PATCH] mm: Pass virtual address to [__]p{te,ud,md}_free_tlb()

On Tue, Jul 28, 2009 at 10:17:40AM +1000, Benjamin Herrenschmidt wrote:
> On Mon, 2009-07-27 at 12:11 -0700, Linus Torvalds wrote:
> > On Thu, 23 Jul 2009, Benjamin Herrenschmidt wrote:
> > > 
> > > Hrm... my powerpc-next branch will contain stuff that depend on it, so
> > > I'll probably have to pull it in though, unless I tell all my
> > > sub-maintainers to also pull from that other branch first :-)
> > 
> > Ok, I'll just apply the patch. It does look obvious enough.
> 
> There seem to be a MIPS and SH breakage as a result but I can't see
> how my patch would have broken it, ie, it looks like the bug was
> already in those two archs. The error is that it complains about a
> duplicate definition of __pmd_free_tlb() between those arch pgalloc.h
> and pgtable-nopmd.h
> 
> For MIPS, when CONFIG_32BIT is set, asm/pgalloc.h redefines
> __pmd_free_tlb despite the fact that it's already defined by
> asm-generic/pgtable-nopmd.h (via via pgtable.h via linux/mm.h).
> 
> I -suspect- what happens is that the compiler, before, would ignore the
> double definition (or maybe just warn) due to the definition being
> strictly identical. With the new argument added, it's no longer the case
> as it's called "a" in asm-generic and "addr" in mips... oops.
> 
> In any case, can Ralf and Paul check if the following patch is correct ?
> 
Yup, that seems to be what happened. I've never seen a warning about this
with any compiler version, otherwise we would have caught this much
earlier. As soon as the addr -> a rename took place it blew up
immediately as a redefinition. Is there a magical gcc flag we can turn on
to warn on identical definitions, even if just for testing?

> >From 41928c7945d855ae0eb053eadad590ab6876847e Mon Sep 17 00:00:00 2001
> From: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> Date: Tue, 28 Jul 2009 10:16:48 +1000
> Subject: [PATCH] mm: Remove duplicate definitions in MIPS and SH
> 
> Those definitions are already provided by asm-generic
> 
> Signed-off-by: Benjamin Herrenschmidt <benh@...nel.crashing.org>

Builds and boots fine, thanks.

Acked-by: Paul Mundt <lethal@...ux-sh.org>
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