> -----Original Message----- > From: Jan Beulich > Sent: Wednesday, August 27, 2014 15:39 PM > >>> On 27.08.14 at 09:30, <de...@microsoft.com> wrote: > > I'm curious about the difference. :-) > > > > sync_set_bit() is only used in drivers/hv/ and drivers/xen/ while set_bit() > > is used in all other places. What makes hv/xen special? > > I guess this would really want to be used by anything communicating > with a hypervisor or a remote driver: set_bit() gets its LOCK prefix > discarded when the local kernel determines it runs on a single CPU > only. Obviously having knowledge of the CPU count inside a VM does > not imply anything about the number of CPUs available to the host, > i.e. stripping LOCK prefixes in that case would be unsafe. > > Jan
Thank you, Juergen and Jan for your quick answers! I didn't realize LOCK_PREFIX is "" for UP. :-) Thanks, -- Dexuan -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
