> On Jun 10, 2015, at 3:57 PM, Ben Pfaff <b...@nicira.com> wrote: > > On Wed, Jun 10, 2015 at 03:51:05PM -0700, Ben Pfaff wrote: >> On Tue, Jun 09, 2015 at 05:24:10PM -0700, Jarno Rajahalme wrote: >>> This patch allows classifier rules to become visible and invisible in >>> specific versions. A 'version' is defined as a positive monotonically >>> increasing integer, which never wraps around. >>> >>> The new 'visibility' attribute replaces the prior 'to_be_removed' and >>> 'visible' attributes. >>> >>> When versioning is not used, the 'version' parameter should be passed >>> as 'CLS_MIN_VERSION' when creating rules, and 'CLS_MAX_VERSION' when >>> looking up flows. >>> >>> This feature enables the support for atomic OpenFlow bundles without >>> significant performance penalty on 64-bit systems. There is a >>> performance decrease in 32-bit systems due to 64-bit atomics used. >>> >>> Signed-off-by: Jarno Rajahalme <jrajaha...@nicira.com> >> >> The two comments >> >> /* clang does not want to read from a const atomic. */ >> >> stand out to me a little, because they imply that this is a special >> property of Clang. I don't think that's true; rather, it's a >> consequence of the C standard definition, which defines atomic "load" >> operations as taking plain types, not const-qualified ones. I think >> that goes back, historically, to the definition of a "side effect" in C: >> >> Accessing a volatile object, modifying an object, modifying a file, >> or calling a function that does any of those operations are all side >> effects, which are changes in the state of the execution >> environment. >> >> That is, *any* access to a volatile object (not just a write) is a side >> effect (and thus cannot be optimized out by the compiler). I get the >> impression that a lot of behavior for atomic types in C11 is related to >> volatile types. >> >> Anyway, personally I'd either drop the comments or just s/clang/C11/. >> >> Acked-by: Ben Pfaff <b...@nicira.com> > > This patch adds an XXX, is that removed in some later patch?
No, I forgot about this. I’ll add this to “Use classifier versioning” patch. Jarno _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev
