Re: [RFC PATCH 02/33] Add sync bitops

From: Andi Kleen
Date: Wed Jul 19 2006 - 08:53:21 EST

On Tuesday 18 July 2006 11:56, Arjan van de Ven wrote:
> On Tue, 2006-07-18 at 00:00 -0700, Chris Wright 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?

I guess because they only need it for a small subset of set_bits.

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