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David Howells wrote: > Nick Piggin <nickpiggin@yahoo.com.au> wrote: > | int atomic_inc_and_test(atomic_t *v); > | int atomic_dec_and_test(atomic_t *v); > | > | These two routines increment and decrement by 1, respectively, the > | given atomic counter. They return a boolean indicating whether the > | resulting counter value was zero or not. > | > | It requires explicit memory barrier semantics around the operation as > | above. > > Note the last paragraph. "It requires" should be "They require", but the > sense would seem to be obvious. However, it's not clear on a second reading > as to whether this is an instruction to the _caller_ or an instruction to the > arch _implementer_. > Yes, I remember Dave M clarified this sometime ago (on lkml I guess). It is a little confusing, but I think the wording is for the implementer's point of view. Dave will pull me up if I'm wrong... > I suppose from reading the abstract at the top: > > | This document is intended to serve as a guide to Linux port maintainers on > | how to implement atomic counter, bitops, and spinlock interfaces properly. > > that it is meant to be read by the implementor and not the user/caller, in which > case, Nick is correct. > > It seems I need to adjust my memory barrier doc, and perhaps I should adjust > atomic_ops.txt too to make it clearer. > I think that would be good. atomic_ops.txt is very useful for API users as well, so if it can be made more general without becoming ambiguous, I'm sure that would be appreciated. Thanks, Nick -- SUSE Labs, Novell Inc. Send instant messages to your online friends http://au.messenger.yahoo.com - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | ||||||||||||
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