Nick Piggin wrote: > On Tuesday 10 June 2008 17:57, Jeremy Fitzhardinge wrote: > >> Nick Piggin wrote: >> >>> On Tuesday 10 June 2008 17:35, Isaku Yamahata wrote: >>> >>>> This patch is ported one from 534:77db69c38249 of linux-2.6.18-xen.hg. >>>> Use wmb instead of rmb to enforce ordering between >>>> evtchn_upcall_pending and evtchn_pending_sel stores >>>> in xen_evtchn_do_upcall(). >>>> >>> There are a whole load of places in the kernel that should be using >>> smp_ variants of memory barriers. This seemed to me like one of them, >>> but I could be wrong. >>> >> No, it needs to be an unconditional barrier. This is synchronizing with >> the hypervisor - even if the kernel is compiled UP, the SMP hypervisor >> may be testing/setting the events pending bits from another (physical) cpu. >> > > OK. What you *really* want is smp_*mb_even_if_compiled_for_UP() ;) > That is, a small set of primitives that are compiled with CONFIG_SMP > (and given some xxx_ prefix to distinguish). >
We already have a set of sync_* for atomic ops which are always locked. > IO barriers are probably the best thing you can use for the moment. > It is conceptually similar, I suppose. J _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linux-foundation.org/mailman/listinfo/virtualization