Re: [PATCH RFC -rcu/dev] hazptrtorture: Release all deferred hazard pointers before stopping

[Paul E. McKenney]

On Mon, Oct 19, 2026 at 07:32:28PM +0200, Andrea Parri wrote:
> On Mon, Oct 19, 2026 at 05:22:54PM +0100, Bradley Morgan wrote:
> > On 19 October 2026 17:20:03 BST, Andrea Parri <parri.andrea@xxxxxxxxx>
> > wrote:
> 
> [...]
> 
> > >Fixes: f23d7b47ced9 ("hazptrtorture: Add kthread to release deferred hazard pointers")
> > >Assisted-by: LLM
> >
> > Why not put this into a series?
> 
> The two patches fix unrelated bugs, touch different files, and apply in
> either order, so I posted them separately.  But both are for -rcu/dev,
> and the test notes in the hazptr patch rely on this one.  I'll send the
> next version as a two-patch series with this patch first, unless Paul
> prefers separate submissions.

I am fine either way.  But whatever you do, please do *not* put them
into the same patch.  ;-)

> [...]
> 
> > >+	/*
> > >+	 * Run until hazptr_torture_cleanup() stops this kthread, not just
> > >+	 * until torture_must_stop(): the writer can be waiting in ->sync()
> > >+	 * for a deferred hazard pointer while it is being stopped.
> > >+	 */
> >
> > Could this be shorter?
> 
> Yes.  The comment in hazptr_torture_cleanup() already says why, so this
> one can just point there:
> 
> 	/* Keep going until hazptr_torture_cleanup() stops us, see there. */
> 
> [...]

The longer one is better.

> > >+	/* The readers have stopped, so nothing new can be deferred. */
> > >+	for_each_possible_cpu(cpu)
> >
> > Is the comment needed? I don't know if it's nessesary.
> 
> I'd keep it.  A reader can defer after the last pass in the loop, and
> kthread_stop() can then end the loop without another pass, so this
> pass is needed; the comment says why one pass is enough.
> 
> > >+	/*
> > >+	 * Stop do_pending only after the writer and the readers: the writer
> > >+	 * may be waiting on hazard pointers that readers deferred.
> > >+	 */
> >
> > May we shorten this? Feel free to bikeshed that one.
> 
> Sure:
> 
> 	/* The writer may wait on hazard pointers that readers deferred. */

And same here.

I am sure that it is possible to create shorter versions that keep all
to the information, but I am OK with Andrea's original versions.

Bradley, Andrea is not a native English speaker and I believe that
you are, so if you want better wording here, please provide it to him.
Perhaps someday he will return the favor should you ever be required to
write in Italian (or German or Ladin, for that matter).  ;-)

							Thanx, Paul

> Thanks for the review,
>   Andrea