Re: [PATCH 1/3] rv/reactors: fix lockdep "Invalid wait context" in rv_react()

[Gabriele Monaco <gmonaco@redhat.com>]

On Tue, 2026-06-23 at 11:38 +0200, Thomas Weißschuh wrote:
> This now allows reactors to take (raw) spinlocks. The original idea was
> to not allow that as a reactor can be called from LD_WAIT_FREE context.
> So I am not sure this is the right fix. Not that I have a better one
> available right now.

As far as I understand it, LD_WAIT_FREE is fairly impossible to apply on
preemptible code (here we see it hit by an interrupt).

Since we kind of have to allow raw spinlock to avoid this (even if we don't take
them explicitly), why wouldn't a reactor ever be allowed to take raw spinlocks?

Technically it wouldn't be wrong to take locks from RV monitors, although most
monitors don't do it explicitly.
If we ever happen to take the wrong lock explicitly from a reactor triggered by
a nasty event (e.g. sched_switch), I believe lockdep would still be complaining
down that path, so we probably don't need to be too strict in rv_react().

Obviously we don't want to disable interrutps for LD_WAIT_FREE to hold either.

Am I missing something?

Thanks,
Gabriele