Messages in this thread | | | Date | Mon, 23 Jan 2023 10:55:17 -0500 | From | Alan Stern <> | Subject | Re: Internal vs. external barriers (was: Re: Interesting LKMM litmus test) |
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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?
Alan
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