Re: [patch] generic-pidhash-2.5.36-D4, BK-curr

From: Oleg Drokin (
Date: Fri Sep 20 2002 - 06:43:47 EST


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?

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