Messages in this thread | | | Date | Mon, 23 Jan 2023 20:40:24 +0100 | Subject | Re: Internal vs. external barriers (was: Re: Interesting LKMM litmus test) | From | Jonas Oberhauser <> |
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On 1/23/2023 4:55 PM, Alan Stern wrote: > On Mon, Jan 23, 2023 at 12:48:42PM +0100, Jonas Oberhauser wrote: >> >> On 1/21/2023 6:36 PM, Alan Stern wrote: >>> On Fri, Jan 20, 2023 at 10:41:14PM +0100, Jonas Oberhauser wrote: >>>> On 1/20/2023 5:18 PM, Alan Stern wrote: >>>>> On Fri, Jan 20, 2023 at 11:13:00AM +0100, Jonas Oberhauser wrote: >>>>>> Perhaps we could say that reading an index without using it later is >>>>>> forbidden? >>>>>> >>>>>> flag ~empty [Srcu-lock];data;rf;[~ domain(data;[Srcu-unlock])] as >>>>>> thrown-srcu-cookie-on-floor >>>>> We already flag locks that don't have a matching unlock. >>>> Of course, but as you know this is completely orthogonal. >>> Yeah, okay. It doesn't hurt to add this check, but the check isn't >>> complete. For example, it won't catch the invalid usage here: >>> >>> P0(srcu_struct *ss) >>> { >>> int r1, r2; >>> >>> r1 = srcu_read_lock(ss); >>> srcu_read_unlock(&ss, r1); >>> r2 = srcu_read_lock(ss); >>> srcu_read_unlock(&ss, r2); >>> } >>> >>> exists (~0:r1=0:r2) >>> >>> On the other hand, how often will people make this sort of mistake in >>> their litmus tests? My guess is not very. >> I currently don't care too much about the incorrect usage of herd (by >> inspecting some final state incorrectly), only incorrect usage in the code. > I'm inclined to add this check to the memory model. Would you prefer to > submit it yourself as a separate patch? Or are you happy to have it > merged with my patch, and if so, do you have a final, preferred form for > the check?
After clearing my confusion, I'm no longer sure if it should be added. If you're still inclined to have it, I would prefer to submit the patch, but I'd like to define the use-cookie relation (= (data|[~Srcu-unlock];rfe)+) and use it also to clarify the srcu match definition (I almost would like to do that anyways :D). Is that ok?
jonas
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