Re: uses of cmpxchg/xadd in spinlock.h and rwsem.h vs. CONFIG_M386

From: Nick Piggin
Date: Tue May 12 2009 - 11:37:44 EST


On Tue, May 12, 2009 at 04:19:00PM +0100, Jan Beulich wrote:
> While looking at a completely different issue I happened to grep for uses of
> xadd, and it would appear to me that there got uses added that would make
> a M386-configured SMP kernel die on an actual i386.
>
> Oh, for the rwsem case I see - it would use the RWSEM_GENERIC_SPINLOCK case
> when selecting M386. But I see nothing similar for the ticket spinlocks - am
> I overlooking something?

Oh, hmm, we do actually attempt to support 386 SMP kernels... I thought
that config wasn't allowed, but looking at the atomic.h code, it has
ifdef fallbacks.

I guess some similar hacks could be added to spinlock.h code.
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