Messages in this thread | | | Date | Wed, 2 Sep 2020 11:54:48 +0800 | From | Boqun Feng <> | Subject | Re: [PATCH kcsan 6/9] tools/memory-model: Expand the cheatsheet.txt notion of relaxed |
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On Mon, Aug 31, 2020 at 11:20:34AM -0700, paulmck@kernel.org wrote: > From: "Paul E. McKenney" <paulmck@kernel.org> > > This commit adds a key entry enumerating the various types of relaxed > operations. > > Signed-off-by: Paul E. McKenney <paulmck@kernel.org> > --- > tools/memory-model/Documentation/cheatsheet.txt | 27 ++++++++++++++----------- > 1 file changed, 15 insertions(+), 12 deletions(-) > > diff --git a/tools/memory-model/Documentation/cheatsheet.txt b/tools/memory-model/Documentation/cheatsheet.txt > index 33ba98d..31b814d 100644 > --- a/tools/memory-model/Documentation/cheatsheet.txt > +++ b/tools/memory-model/Documentation/cheatsheet.txt > @@ -5,7 +5,7 @@ > > Store, e.g., WRITE_ONCE() Y Y > Load, e.g., READ_ONCE() Y Y Y Y > -Unsuccessful RMW operation Y Y Y Y > +Relaxed 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 > @@ -17,14 +17,17 @@ 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: 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 > +Key: Relaxed: A relaxed operation is either a *_relaxed() RMW > + operation, an unsuccessful RMW operation, or one of > + the atomic_read() and atomic_set() family of operations.
To be accurate, atomic_set() doesn't return any value, so it cannot be ordered against DR and DW ;-)
I think we can split the Relaxed family into two groups:
void Relaxed: atomic_set() or atomic RMW operations that don't return any value (e.g atomic_inc())
non-void Relaxed: a *_relaxed() RMW operation, an unsuccessful RMW operation, or atomic_read().
And "void Relaxed" is similar to WRITE_ONCE(), only has "Self" and "SV" equal "Y", while "non-void Relaxed" plays the same rule as "Relaxed" in this patch.
Thoughts?
Regards, Boqun
> + 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 > -- > 2.9.5 >
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