Re: [PATCH] mm/mmu_notifier: Remove non_block_start/end() from notifier invocation

[David Woodhouse]

On Wed, 2026-08-26 at 09:32 +0200, Sebastian Andrzej Siewior wrote:
> On 2026-08-25 13:51:14 [-0700], Paul E. McKenney wrote:
> > Very good, preemption disabling it is!  It is quite possible that the
> > PREEMPT_RT guys will need something else, but one thing at a time.
> 
> This reminds me of classic RCU ;) It might work in this use case but I
> am afraid that other users might come along where it actually hurts.
> With PREEMPT LAZY the preemption within the read-section should
> hopefully be the exception.

Given the way that PREEMPT_RT treats other locks like spinlocks and
rwlocks — turning them into sleeping locks — I suspect it makes most
sense, and is consistent, to also turn rcu_read_lock_atomic() and
synchronize_rcu_atomic() into plain rcu_read_lock() and
try_synchronize_srcu()+synchronize_scru_expedited().

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