> -----Original Message----- > From: Jan Beulich [mailto:[email protected]] > Sent: Wednesday, August 27, 2014 12:39 AM > To: Dexuan Cui > Cc: [email protected]; KY Srinivasan; [email protected]; linux- > [email protected] > Subject: Re: sync_set_bit() vs set_bit() -- what's the difference? > > >>> On 27.08.14 at 09:30, <[email protected]> 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.
That is exactly the case for Hyper-V (and Xen). K. Y -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
