Messages in this thread | | | Date | Fri, 20 Jan 2023 09:30:54 -0800 | From | "Paul E. McKenney" <> | Subject | Re: Internal vs. external barriers (was: Re: Interesting LKMM litmus test) |
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On Fri, Jan 20, 2023 at 11:14:06AM -0500, Alan Stern wrote: > On Thu, Jan 19, 2023 at 07:55:21PM -0800, Paul E. McKenney wrote: > > And for some initial tests: > > > > https://github.com/paulmckrcu/litmus/blob/master/manual/kernel/C-srcu-nest-1.litmus > > > > "Flag multiple-srcu-matches" but otherwise OK. > > As a "hail Mary" exercise, I used r4 for the second SRCU > > read-side critical section, but this had no effect. > > (This flag is expected and seen for #4 below.) > > Jonas is right about the reason for this. Also, his suggestion for > fixing the check in lock.cat makes sense.
Very good!
> My revised patch is below.
Thank you! Are you OK with my putting this on a not-for-mainline branch for experimental purposes?
> > https://github.com/paulmckrcu/litmus/blob/master/manual/kernel/C-srcu-nest-2.litmus > > https://github.com/paulmckrcu/litmus/blob/master/manual/kernel/C-srcu-nest-3.litmus > > https://github.com/paulmckrcu/litmus/blob/master/manual/kernel/C-srcu-nest-4.litmus > > https://github.com/paulmckrcu/litmus/blob/master/manual/kernel/C-srcu-nest-5.litmus > > > > All as expected. > > > > https://github.com/paulmckrcu/litmus/blob/master/manual/kernel/C-srcu-nest-6.litmus > > > > Get "Flag unbalanced-srcu-lock" and "Flag unbalanced-srcu-unlock", > > but this is srcu_down_read() and srcu_up_read(), where this should > > be OK. Ah, but I need to do the release/acquire/filter trick. Once > > I did that, it works as expected. > > > > https://github.com/paulmckrcu/litmus/blob/master/manual/kernel/C-srcu-nest-7.litmus > > https://github.com/paulmckrcu/litmus/blob/master/manual/kernel/C-srcu-nest-8.litmus > > > > Both as expected. > > > > Getting there!!! > > Good news.
And all of the litmus-repo tests up to ten processes passed. Woo-hoo!!!
Thanx, Paul
> Alan > > > > Index: usb-devel/tools/memory-model/linux-kernel.bell > =================================================================== > --- usb-devel.orig/tools/memory-model/linux-kernel.bell > +++ usb-devel/tools/memory-model/linux-kernel.bell > @@ -53,38 +53,31 @@ let rcu-rscs = let rec > in matched > > (* Validate nesting *) > -flag ~empty Rcu-lock \ domain(rcu-rscs) as unbalanced-rcu-locking > -flag ~empty Rcu-unlock \ range(rcu-rscs) as unbalanced-rcu-locking > +flag ~empty Rcu-lock \ domain(rcu-rscs) as unbalanced-rcu-lock > +flag ~empty Rcu-unlock \ range(rcu-rscs) as unbalanced-rcu-unlock > > (* Compute matching pairs of nested Srcu-lock and Srcu-unlock *) > -let srcu-rscs = let rec > - unmatched-locks = Srcu-lock \ domain(matched) > - and unmatched-unlocks = Srcu-unlock \ range(matched) > - and unmatched = unmatched-locks | unmatched-unlocks > - and unmatched-po = ([unmatched] ; po ; [unmatched]) & loc > - and unmatched-locks-to-unlocks = > - ([unmatched-locks] ; po ; [unmatched-unlocks]) & loc > - and matched = matched | (unmatched-locks-to-unlocks \ > - (unmatched-po ; unmatched-po)) > - in matched > +let carry-srcu-data = (data ; [~ Srcu-unlock] ; rf)* > +let srcu-rscs = ([Srcu-lock] ; carry-srcu-data ; data ; [Srcu-unlock]) & loc > > (* Validate nesting *) > -flag ~empty Srcu-lock \ domain(srcu-rscs) as unbalanced-srcu-locking > -flag ~empty Srcu-unlock \ range(srcu-rscs) as unbalanced-srcu-locking > +flag ~empty Srcu-lock \ domain(srcu-rscs) as unbalanced-srcu-lock > +flag ~empty Srcu-unlock \ range(srcu-rscs) as unbalanced-srcu-unlock > +flag ~empty (srcu-rscs^-1 ; srcu-rscs) \ id as multiple-srcu-matches > > (* Check for use of synchronize_srcu() inside an RCU critical section *) > flag ~empty rcu-rscs & (po ; [Sync-srcu] ; po) as invalid-sleep > > (* Validate SRCU dynamic match *) > -flag ~empty different-values(srcu-rscs) as srcu-bad-nesting > +flag ~empty different-values(srcu-rscs) as bad-srcu-value-match > > (* Compute marked and plain memory accesses *) > let Marked = (~M) | IW | Once | Release | Acquire | domain(rmw) | range(rmw) | > - LKR | LKW | UL | LF | RL | RU > + LKR | LKW | UL | LF | RL | RU | Srcu-lock | Srcu-unlock > let Plain = M \ Marked > > (* Redefine dependencies to include those carried through plain accesses *) > -let carry-dep = (data ; rfi)* > +let carry-dep = (data ; [~ Srcu-unlock] ; rfi)* > let addr = carry-dep ; addr > let ctrl = carry-dep ; ctrl > let data = carry-dep ; data > Index: usb-devel/tools/memory-model/linux-kernel.def > =================================================================== > --- usb-devel.orig/tools/memory-model/linux-kernel.def > +++ usb-devel/tools/memory-model/linux-kernel.def > @@ -49,8 +49,10 @@ synchronize_rcu() { __fence{sync-rcu}; } > synchronize_rcu_expedited() { __fence{sync-rcu}; } > > // SRCU > -srcu_read_lock(X) __srcu{srcu-lock}(X) > -srcu_read_unlock(X,Y) { __srcu{srcu-unlock}(X,Y); } > +srcu_read_lock(X) __load{srcu-lock}(*X) > +srcu_read_unlock(X,Y) { __store{srcu-unlock}(*X,Y); } > +srcu_down_read(X) __load{srcu-lock}(*X) > +srcu_up_read(X,Y) { __store{srcu-unlock}(*X,Y); } > synchronize_srcu(X) { __srcu{sync-srcu}(X); } > synchronize_srcu_expedited(X) { __srcu{sync-srcu}(X); } > > Index: usb-devel/tools/memory-model/lock.cat > =================================================================== > --- usb-devel.orig/tools/memory-model/lock.cat > +++ usb-devel/tools/memory-model/lock.cat > @@ -36,9 +36,9 @@ let RU = try RU with emptyset > (* Treat RL as a kind of LF: a read with no ordering properties *) > let LF = LF | RL > > -(* There should be no ordinary R or W accesses to spinlocks *) > -let ALL-LOCKS = LKR | LKW | UL | LF | RU > -flag ~empty [M \ IW] ; loc ; [ALL-LOCKS] as mixed-lock-accesses > +(* There should be no ordinary R or W accesses to spinlocks or SRCU structs *) > +let ALL-LOCKS = LKR | LKW | UL | LF | RU | Srcu-lock | Srcu-unlock | Sync-srcu > +flag ~empty [M \ IW \ ALL-LOCKS] ; loc ; [ALL-LOCKS] as mixed-lock-accesses > > (* Link Lock-Reads to their RMW-partner Lock-Writes *) > let lk-rmw = ([LKR] ; po-loc ; [LKW]) \ (po ; po)
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