Messages in this thread | | | Date | Tue, 26 Jun 2018 12:31:46 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH tip/core/rcu 16/27] rcu: Add comment documenting how rcu_seq_snap works |
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On Tue, Jun 26, 2018 at 09:21:13PM +0200, Peter Zijlstra wrote: > On Tue, Jun 26, 2018 at 11:08:55AM -0700, Paul E. McKenney wrote: > > On Tue, Jun 26, 2018 at 07:14:54PM +0200, Peter Zijlstra wrote: > > > On Mon, Jun 25, 2018 at 05:35:02PM -0700, Paul E. McKenney wrote: > > > > From: "Joel Fernandes (Google)" <joel@joelfernandes.org> > > > > > > > > rcu_seq_snap may be tricky to decipher. Lets document how it works with > > > > an example to make it easier. > > > > > > Since you had me looking at them functions; why isn't rcu_seq_snap() > > > using smp_load_acquire() and rcu_seq_end() using smp_store_release() ? > > > Their respective comments seem to suggest that would be sufficent. > > > > I do not believe that this would suffice. Would it make sense to refer > > to Documentation/RCU/Design/Memory-Ordering in the comment header? > > No, because I can't read that thing in an editor. > > > Except that this would invite sprinkling this pathname far and wide... > > > > The key point is that these functions are part of the any-to-any > > memory-ordering guarantee that RCU grace periods provide. > > Then the existing comment is misleading and really needs change.
Would it be sufficient to add something like "The memory barrier is required to support the many-to-many ordering guaranteed by RCU grace periods"?
Thanx, Paul
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