Re: [PATCH v3 3/3] md: protect md_thread with rcu

[Yu Kuai]

Hi,

在 2023/03/31 9:08, Yu Kuai 写道:
> Hi, Logan!
>
> 在 2023/03/31 3:35, Logan Gunthorpe 写道:
> > A couple points:
> >
> > I don't think we need a double pointer here. rcu_dereference() doesn't
> > actually do anything but annotate the fact that we are accessing a
> > pointer protected by rcu. It does require annotations on that pointer
> > (__rcu) which is checked by sparse (I suspect this patch will produce a
> > lot of sparse errors from kbuild bot).
> >
> > I think all we need is:
> >
> > void md_wakeup_thread(struct md_thread __rcu *rthread)
> > {
> >     struct md_thread *thread;
> >
> >     rcu_read_lock();
> >     thread = rcu_dereference(rthread);
> >     ...
> >     rcu_read_unlock();
> >
> > }
> >
> > The __rcu annotation will have to be added to all the pointers this
> > function is called on as well as to md_register_thread() and
> > md_unregister_thread(). And anything else that uses those pointers.
> > Running sparse on the code and eliminating all new errors for the patch
> > is important.
>
> Yes, you're right, I'll remove patch 2 and update patch 3. And I'll try
> to run sparse before sending the new version.

By the way, I observed lots of sparse errors and warnings for current
code, will it make sense to fix them?

Thanks,
Kuai