"Volatile behaviour" itself isn't consistently defined (at least definitely not consistently implemented in various gcc versions across platforms),
It should be consistent across platforms; if not, file a bug please.
but it is /expected/ to mean something like: "ensure that every such access actually goes all the way to memory, and is not re-ordered w.r.t. to other accesses, as far as the compiler can take care of these". The last "as far as compiler can take care" disclaimer comes about due to CPUs doing their own re-ordering nowadays.
You can *expect* whatever you want, but this isn't in line with reality at all. volatile _does not_ make accesses go all the way to memory. volatile _does not_ prevent reordering wrt other accesses. What volatile does are a) never optimise away a read (or write) to the object, since the data can change in ways the compiler cannot see; and b) never move stores to the object across a sequence point. This does not mean other accesses cannot be reordered wrt the volatile access. If the abstract machine would do an access to a volatile- qualified object, the generated machine code will do that access too. But, for example, it can still be optimised away by the compiler, if it can prove it is allowed to. If you want stuff to go all the way to memory, you need some architecture-specific flush sequence; to make a store globally visible before another store, you need mb(); before some following read, you need mb(); to prevent reordering you need a barrier. Segher - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
