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Date: Tue, 18 Jul 2006 11:18:45 +0100 From: Keir Fraser <Keir.Fraser@...cam.ac.uk> To: Arjan van de Ven <arjan@...radead.org> Cc: Ian Pratt <ian.pratt@...source.com>, Jeremy Fitzhardinge <jeremy@...p.org>, xen-devel@...ts.xensource.com, linux-kernel@...r.kernel.org, virtualization@...ts.osdl.org, Christoph Lameter <clameter@....com>, Chris Wright <chrisw@...s-sol.org>, Andrew Morton <akpm@...l.org> Subject: Re: [RFC PATCH 02/33] Add sync bitops On 18 Jul 2006, at 10:56, Arjan van de Ven wrote: >> plain text document attachment (synch-ops) >> Add "always lock'd" implementations of set_bit, clear_bit and >> change_bit and the corresponding test_and_ functions. Also add >> "always lock'd" implementation of cmpxchg. These give guaranteed >> strong synchronisation and are required for non-SMP kernels running on >> an SMP hypervisor. > > Hi, > > this sounds really like the wrong approach; you know you're compiling > for xen, so why not just make set_bit() and the others use the lock'd > instructions at compile time? Then all users of bitops would unnecessarily pay the price when running in a single-CPU guest. Only a few of our bitops callers absolutely require the lock prefix in all cases. -- Keir - 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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