Re: [PATCH 7/8] mm/slab: introduce deferred submission of rcu sheaves

["Harry Yoo (Oracle)" <harry@kernel.org>]

On Tue, Apr 21, 2026 at 03:51:02PM -0700, Alexei Starovoitov wrote:
> On Thu Apr 16, 2026 at 2:10 AM PDT, Harry Yoo (Oracle) wrote:
> > Instead of falling back when the rcu sheaf becomes full, implement
> > deferred submission of rcu sheaves. If kfree_rcu_sheaf() is invoked
> > by kfree_rcu_nolock() (!allow_spin) and IRQs are disabled, the CPU might
> > be in the middle of call_rcu() and thus defer call_rcu() with irq_work.
> >
> > Submit all deferred RCU sheaves to call_rcu() before calling
> > rcu_barrier() to ensure the promise of kvfree_rcu_barrier().
> >
> > An alternative approach could be to implement this in the RCU subsystem,
> > tracking if it's safe to call call_rcu() and allowing falling back to
> > deferred call_rcu() at the cost of more expensive rcu_barrier() calls.
> 
> Yeah. call_rcu_nolock() will be really handy here and in other places.

*curiously watching whether RCU folks show interest, so that he could
 drop ad-hoc code in slab*

> When you respin pls pick some tree that sashiko knows about.

Yeah, adding base-commit id appareantly didn't help.
Sashiko doesn't know that we have the slab tree :'(

> So it can apply it all and review it all.
> Currently it reviewed only patch 1 and failed to apply the most interesting 4+
> https://sashiko.dev/#/patchset/20260416091022.36823-1-harry%40kernel.org

I heard that at least Sashiko knows about mm, linux-next, and mainline
trees. Will try linux-next next time.

-- 
Cheers,
Harry / Hyeonggon