Messages in this thread | | | Date | Wed, 05 Apr 2006 15:51:06 -0700 (PDT) | Subject | Re: [PATCH] Keys: Improve usage of memory barriers and remove IRQ disablement | From | "David S. Miller" <> |
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From: Nick Piggin <nickpiggin@yahoo.com.au> Date: Wed, 05 Apr 2006 19:23:58 +1000
> 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...
Any routine which returns state must have the barriers in the arch implementation. These two routines returns state. - 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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