On Thu, Oct 08, 2020 at 10:01:48AM -0400, Alan Stern wrote: > On Wed, Oct 07, 2020 at 07:50:25PM -0700, Paul E. McKenney wrote: > > There are some distractions at the moment. > > > > Please see below. If this is not exactly correct, I will use "git rm" > > and let you submit the patch as you wish. > > > > Thanx, Paul > > > > ------------------------------------------------------------------------ > > > > commit dc0119c24b64f9d541b94ba5d17eec0cbc265bfa > > Author: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> > > Date: Tue Oct 6 09:38:37 2020 -0700 > > > > manual/kernel: Add LB data dependency test with no intermediate variable > > > > Test whether herd7 can detect a data dependency when there is no > > intermediate local variable, as in WRITE_ONCE(*x, READ_ONCE(*y)). > > Commit 0f3f8188a326 in herdtools fixed an oversight which caused such > > dependencies to be missed. > > > > Signed-off-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> > > Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx> > > > > diff --git a/manual/kernel/C-LB+mb+data.litmus b/manual/kernel/C-LB+mb+data.litmus > > new file mode 100644 > > index 0000000..e9e24e0 > > --- /dev/null > > +++ b/manual/kernel/C-LB+mb+data.litmus > > @@ -0,0 +1,27 @@ > > +C LB+mb+data > > +(* > > + * Result: Never > > + * > > + * Versions of herd7 prior to commit 0f3f8188a326 ("[herd] Fix dependency > > + * definition") recognize data dependencies only when they flow through > > + * an intermediate local variable. Since the dependency in P1 doesn't, > > + * those versions get the wrong answer for this test. > > + *) > > + > > +{} > > + > > +P0(int *x, int *y) > > +{ > > + int r1; > > + > > + r1 = READ_ONCE(*x); > > + smp_mb(); > > + WRITE_ONCE(*y, r1); > > +} > > + > > +P1(int *x, int *y) > > +{ > > + WRITE_ONCE(*x, READ_ONCE(*y)); > > +} > > + > > +exists (0:r1=1) > > Okay, that's exactly what it should be. :-) Whew!!! ;-) Thanx, Paul