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

[David Woodhouse]

On 26 August 2026 17:28:27 BST, "Paul E. McKenney" <paulmck@xxxxxxxxxx> wrote:
>On Wed, Aug 26, 2026 at 08:05:06AM -0700, Paul E. McKenney wrote:
>> On Wed, Aug 26, 2026 at 08:38:27AM +0100, David Woodhouse wrote:
>> > 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().
>> 
>> That makes a lot of sense to me.
>
>Another option is to instead fall back to non-atomic SRCU.

That's exactly what I thought I was suggesting; I think I left an 's' out though :)