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

[David Woodhouse]

On Tue, 2026-08-11 at 12:24 -0300, Jason Gunthorpe wrote:
> It is documented to be like this, even if it is hard to test..

So don't change your documentation :)

> Even for normal blocking notifiers you should not be using
> synchronize_rcu().

This is SRCU not RCU, and the read-side sections are converted from
rwlocks and never had any allocations inside them anyway. But under RT,
rwlocks can spin too, which causes all kinds of fun and that's what
pushed us to look at SRCU... which actually performs a whole lot better
at scale too.

But that's a separate thread. If you have input on how KVM should and
should not be dealing with that issue, it would be welcome in the
context of the specific patches which are doing so...

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