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Date: Mon, 11 Dec 2006 05:03:34 +0100 From: Nick Piggin <npiggin@...e.de> To: David Howells <dhowells@...hat.com> Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, linux-arch@...r.kernel.org, Linus Torvalds <torvalds@...l.org>, Andrew Morton <akpm@...l.org> Subject: Re: [patch][rfc] rwsem: generic rwsem On Fri, Dec 08, 2006 at 01:58:42PM +0000, David Howells wrote: > Nick Piggin <npiggin@...e.de> wrote: > > > > Look at how the counter works in the XADD-based version. That's the way > > > it is *because* I'm using XADD. That's quite limiting. > > > > Not really. ll/sc architectures "emulate" xadd the same as they would > > emulate a spinlock. There is nothing suboptimal about it. > > Yes, really. You've missed the point entirely. Look at *how* the counter > *works*. OK, I've looked but I can't see how you would make it more optimal on an ll/sc architecture. The atomic_add_return variant has no more atomic or barrier operations than the spinlock one, and it has less loads and branches. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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