Re: [PATCH 19/24] rcu/tree: Support reclaim for head-less object

Uladzislau Rezki
2020-05-04T16:56:38Z

> >
> > For single argument we can drop the lock before the entry to the page
> > allocator. Because it follows might_sleep() anotation we avoid of having
> > a situation when spinlock(rt mutex) is taken from any atomic context.
> >
> > Since the lock is dropped the current context can be interrupted by
> > an IRQ which in its turn can also call kvfree_rcu() on current CPU.
> > In that case it must be double argument(single is not allowed) kvfree_rcu()
> > call. For PREEMPT_RT if no cache everything is reverted to rcu_head usage,
> > i.e. the entry to page allocator is bypassed.
> >
> > It can be addressed as a separate patch and send out later on if we
> > are on the same page.
> >
> > Paul, Joel what are your opinions?
>
> I strongly prefer that it be removed from the series. I do understand
> that this is a bit more hassle right now, but this does help avoid
> confusion in the future, plus perhaps also avoiding issues with future
> bisections.
>
We have already decided to get rid of it, i mean small allocations(dynamic
rcu_head attaching). I will exclude it from next patch-set version.

--
Vlad Rezki