Re: [PATCH tip/core/rcu 1/3] rcu-tasks: *_ONCE() for rcu_tasks_cbs_head

[Paul E. McKenney]

On Tue, Feb 18, 2020 at 09:11:42PM +0100, Peter Zijlstra wrote:
> On Tue, Feb 18, 2020 at 08:27:19AM -0800, Paul E. McKenney wrote:
> > On Tue, Feb 18, 2020 at 08:56:48AM +0100, Peter Zijlstra wrote:
> 
> > > I just took offence at the Changelog wording. It seems to suggest there
> > > actually is a problem, there is not.
> > 
> > Quoting the changelog: "Not appropriate for backporting due to failure
> > being unlikely."
> 
> That implies there is failure, however unlikely.
> 
> In this particular case there is absolutely no failure, except perhaps
> in KCSAN. This patch is a pure annotation such that KCSAN can understand
> the code.
> 
> Like said, I don't object to the actual patch, but I do think it is
> important to call out false negatives or to describe the actual problem
> found.

I don't feel at all comfortable declaring that there is absolutely
no possibility of failure.

							Thanx, Paul