Messages in this thread Patch in this message | | | Date | Thu, 3 Sep 2020 19:39:55 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH kcsan 6/9] tools/memory-model: Expand the cheatsheet.txt notion of relaxed |
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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.
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
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