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

[Andrew Morton]

Ingo Molnar wrote:
> 
> On Fri, 20 Sep 2002, Oleg Drokin 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.
> Then every architecture can enhance the implementation if it wishes to.
> 

That would be good, but wouldn't we then need a special per-arch
"cmpxchngable" type, like atomic_t?

Seems that just doing compare-and-exchange on a bare page* might force
some architectures to use a global lock.