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Message-ID: <Pine.LNX.4.64.0612080919220.16029@schroedinger.engr.sgi.com> Date: Fri, 8 Dec 2006 09:23:57 -0800 (PST) From: Christoph Lameter <clameter@....com> To: Russell King <rmk+lkml@....linux.org.uk> cc: David Howells <dhowells@...hat.com>, Nick Piggin <nickpiggin@...oo.com.au>, torvalds@...l.org, akpm@...l.org, linux-arm-kernel@...ts.arm.linux.org.uk, linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org Subject: Re: [PATCH] WorkStruct: Implement generic UP cmpxchg() where an arch doesn't support it On Fri, 8 Dec 2006, Russell King wrote: > As proven previously the reverse is also true. And as shown previously > the cheaper out of the two for all platforms is the LL/SC based > implementation, where the architecture specific implementation can > be _either_ LL/SC based or cmpxchg based depending on what is > supported in their hardware. As also shown in this thread: There are restrictions on what you can do between ll/sc. You would not want to use C code there. ll/sc is an thing that needs to be restricted to asm code. So this is not a viable proposal at all. ll/sc is useful to construct various atomic functions but cannot be directly used in C code. cmpxchg can be effectively realized using ll/sc. - 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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