Re: [PATCH kcsan 6/9] tools/memory-model: Expand the cheatsheet.txt notion of relaxed

Paul E. McKenney
2020-09-04T19:56:10Z

On Fri, Sep 04, 2020 at 10:47:17AM +0800, Boqun Feng wrote:
> On Thu, Sep 03, 2020 at 07:39:55PM -0700, Paul E. McKenney wrote:
> > On Fri, Sep 04, 2020 at 08:59:21AM +0800, Boqun Feng wrote:
> > > On Thu, Sep 03, 2020 at 04:30:37PM -0700, Paul E. McKenney wrote:
> >
> > [ . . . ]
> >
> > > > How about like this, adding "Relaxed" to the WRITE_ONCE() and READ_ONCE()
> > > > rows and "RMW" to the "Relaxed operation" row?
> > > >
> > >
> > > Much better now, thanks! However ...
> > >
> > > > The file contents are followed by a diff against the previous version.
> > > >
> > > > Thanx, Paul
> > > >
> > > > ------------------------------------------------------------------------
> >
> > [ . . . ]
> >
> > > > Key: Relaxed: A relaxed operation is either a *_relaxed() RMW
> > > > operation, an unsuccessful RMW operation, READ_ONCE(),
> > > > WRITE_ONCE(), or one of the atomic_read() and
> > > > atomic_set() family of operations.
> > >
> > > And:
> > > a RMW operation that doesn't return any value (e.g
> > > atomic_inc()), IOW it's a void Relaxed operation.
> >
> > Good point! Please see below.
> >
>
> Looks good to me ;-)
>
>
> Acked-by: Boqun Feng <boqun.feng@gmail.com>

Applied, thank you!

Thanx, Paul

> Regards,
> Boqun
>
> > Thanx, Paul
> >
> > ------------------------------------------------------------------------
> >
> > Prior Operation Subsequent Operation
> > --------------- ---------------------------
> > C Self R W RMW Self R W DR DW RMW SV
> > -- ---- - - --- ---- - - -- -- --- --
> >
> > Relaxed store Y Y
> > Relaxed load Y Y Y Y
> > Relaxed RMW operation Y Y Y Y
> > rcu_dereference() Y Y Y Y
> > Successful *_acquire() R Y Y Y Y Y Y
> > Successful *_release() C Y Y Y W Y
> > smp_rmb() Y R Y Y R
> > smp_wmb() Y W Y Y W
> > smp_mb() & synchronize_rcu() CP Y Y Y Y Y Y Y Y
> > Successful full non-void RMW CP Y Y Y Y Y Y Y Y Y Y Y
> > smp_mb__before_atomic() CP Y Y Y a a a a Y
> > smp_mb__after_atomic() CP a a Y Y Y Y Y Y
> >
> >
> > Key: Relaxed: A relaxed operation is either READ_ONCE(), WRITE_ONCE(),
> > a *_relaxed() RMW operation, an unsuccessful RMW
> > operation, a non-value-returning RMW operation such
> > as atomic_inc(), or one of the atomic*_read() and
> > atomic*_set() family of operations.
> > C: Ordering is cumulative
> > P: Ordering propagates
> > R: Read, for example, READ_ONCE(), or read portion of RMW
> > W: Write, for example, WRITE_ONCE(), or write portion of RMW
> > Y: Provides ordering
> > a: Provides ordering given intervening RMW atomic operation
> > DR: Dependent read (address dependency)
> > DW: Dependent write (address, data, or control dependency)
> > RMW: Atomic read-modify-write operation
> > SELF: Orders self, as opposed to accesses before and/or after
> > SV: Orders later accesses to the same variable
> >
> > ------------------------------------------------------------------------
> >
> > diff --git a/tools/memory-model/Documentation/cheatsheet.txt b/tools/memory-model/Documentation/cheatsheet.txt
> > index 4146b8d..99d0087 100644
> > --- a/tools/memory-model/Documentation/cheatsheet.txt
> > +++ b/tools/memory-model/Documentation/cheatsheet.txt
> > @@ -17,10 +17,11 @@ smp_mb__before_atomic() CP Y Y Y a a a a Y
> > smp_mb__after_atomic() CP a a Y Y Y Y Y Y
> >
> >
> > -Key: Relaxed: A relaxed operation is either a *_relaxed() RMW
> > - operation, an unsuccessful RMW operation, READ_ONCE(),
> > - WRITE_ONCE(), or one of the atomic_read() and
> > - atomic_set() family of operations.
> > +Key: Relaxed: A relaxed operation is either READ_ONCE(), WRITE_ONCE(),
> > + a *_relaxed() RMW operation, an unsuccessful RMW
> > + operation, a non-value-returning RMW operation such
> > + as atomic_inc(), or one of the atomic*_read() and
> > + atomic*_set() family of operations.
> > C: Ordering is cumulative
> > P: Ordering propagates
> > R: Read, for example, READ_ONCE(), or read portion of RMW