Jeremy Fitzhardinge wrote: > Gerd Hoffmann wrote: >> I'm looking at the guest side of the issue right now, trying to identify >> common code, and while doing so noticed that xen does the >> version-check-loop in both get_time_values_from_xen(void) and >> xen_clocksource_read(void), and I can't see any obvious reason for that. >> The loop in xen_clocksource_read(void) is not needed IMHO. Can I >> drop it? > > No. The get_nsec_offset() needs to be atomic with respect to the > get_time_values() parameters.
Hmm, I somehow fail to see a case where it could be non-atomic ... get_time_values() copies a consistent snapshot, thus xen_clocksource_read() doesn't race against xen updating the fields. The snapshot is in a per-cpu variable, thus it doesn't race against other guest vcpus running get_time_values() at the same time. > There could be a loopless > __get_time_values() for use in this case, but given that it almost never > loops, I don't think its worthwhile. "in this case" ??? I'm confused. There is only a single user of get_nsec_offset(), which is xen_clocksource_read() ... cheers, Gerd -- http://kraxel.fedorapeople.org/xenner/ ------------------------------------------------------------------------- This SF.net email is sponsored by the 2008 JavaOne(SM) Conference Don't miss this year's exciting event. There's still time to save $100. Use priority code J8TL2D2. http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
