On Thu, Aug 16, 2007 at 09:34:41AM -0700, Paul E. McKenney wrote: > > The compiler can also reorder non-volatile accesses. For an example > patch that cares about this, please see: > > http://lkml.org/lkml/2007/8/7/280 > > This patch uses an ORDERED_WRT_IRQ() in rcu_read_lock() and > rcu_read_unlock() to ensure that accesses aren't reordered with respect > to interrupt handlers and NMIs/SMIs running on that same CPU.
Good, finally we have some code to discuss (even though it's not actually in the kernel yet). First of all, I think this illustrates that what you want here has nothing to do with atomic ops. The ORDERED_WRT_IRQ macro occurs a lot more times in your patch than atomic reads/sets. So *assuming* that it was necessary at all, then having an ordered variant of the atomic_read/atomic_set ops could do just as well. However, I still don't know which atomic_read/atomic_set in your patch would be broken if there were no volatile. Could you please point them out? Cheers, -- Visit Openswan at http://www.openswan.org/ Email: Herbert Xu ~{PmV>HI~} <[EMAIL PROTECTED]> Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt - 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
