Re: [PATCH] notifier: Make atomic_notifiers use raw_spinlock

[Sebastian Andrzej Siewior]

On 2021-08-06 20:02:42 [+0200], Peter Zijlstra wrote:
> On Fri, Aug 06, 2021 at 04:07:18PM +0200, Sebastian Andrzej Siewior wrote:
> > What do we do with this?
> > Do we merge this as-is, add another "robust atomic notifier" using only
> > raw_spinlock_t for registration and notification (for only
> > cpu_pm_notifier_chain) instead of switching to raw_spinlock_t for all
> > atomic notifier in -tree?
> 
> Right, so the problem I see with this is that
> notifier_chain_{,un}register() are O(n). Hardly something we should be
> putting under raw_spin_lock :/

Yup, pretty much. So we make one robust notifier for
cpu_pm_notifier_chain?

Sebastian