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

[Peter Zijlstra]

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.