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Date: Fri, 20 Sep 2002 15:43:47 +0400
From: Oleg Drokin <green@namesys.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: Linus Torvalds <torvalds@transmeta.com>,
       William Lee Irwin III <wli@holomorphy.com>,
       linux-kernel@vger.kernel.org
Subject: Re: [patch] generic-pidhash-2.5.36-D4, BK-curr
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Hello!

On Fri, Sep 20, 2002 at 11:40:16AM +0200, Ingo Molnar wrote:
> > > +			if (cmpxchg(&map->page, NULL, page))
> > > +				free_page(page);
> > Note that this piece breaks compilation for every arch that does not
> > have cmpxchg implementation.
> > This is the case with x86 (with CONFIG_X86_CMPXCHG undefined, e.g. i386),
> > ARM, CRIS, m68k, MIPS, MIPS64, PARISC, s390, SH, sparc32, UML (for x86).
> we need a cmpxchg() function in the generic library, using a spinlock.  

But this is not safe for arches that provides SMP but does not provide
cmpxchg in hadware, right?
I mean it is only safe to use such spinlock-based function if
all other places read and write this value via special functions that are
also taking this spinlock.
Do you think we can count on this?

Bye,
    Oleg
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