Re: [PATCH tip/core/rcu 1/4] doc: Present the role of READ_ONCE()

[Paul E. McKenney]

On Mon, Nov 09, 2020 at 01:21:33PM +0100, Peter Zijlstra wrote:
> On Thu, Nov 05, 2020 at 03:05:07PM -0800, paulmck@xxxxxxxxxx wrote:
> > From: "Paul E. McKenney" <paulmck@xxxxxxxxxx>
> > 
> > This commit adds an explanation of the special cases where READ_ONCE()
> > may be used in place of a member of the rcu_dereference() family.
> 
> I am confused, there is no actual difference between rcu_dereference()
> and READ_ONCE() today. So we _may_ use READ_ONCE() at all times.
> 
> Now granted, we probably don't want that, but that does leave me
> somewhat confused vs the wording here.

There is a difference from the viewpoint of both lockdep and sparse.

Or am I missing your point?

							Thanx, Paul