[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] Re: [RFC PATCH 05/35] Add sync bitops
On Wednesday 10 May 2006 00:56, Christoph Lameter wrote: > On Tue, 9 May 2006, Chris Wright wrote: > > > 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. > > Could you explain why this is done and what is exactly meant with "always > looked"? Wh the performance impact? When UP guest runs on SMP hypervisor they still need the LOCK prefix to talk to the hypervisor through shared memory in a smp safe way. Normally UP kernels don't use any LOCK prefixes. I suggested to refactor the bitops this way earlier for this. -Andi _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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