Re: [PATCH 03/21] rcu: Add a note about noinstr VS unsafe eqs functions

[Peter Zijlstra]

On Tue, May 03, 2022 at 12:00:33PM +0200, Frederic Weisbecker wrote:
> Some RCU functions enter or exit into/from RCU idle mode while using
> trace-able and lockdep-aware IRQs (un-)masking. This could be easily
> solved with using raw versions of local_irq_*() but we would then
> lose some precious debugging informations.
> 
> Another possible way to solve this may consist in using rude RCU-tasks
> in lockdep and irqsoff tracing.
> 
> In any case and until this get solved, those RCU functions can't get
> tagged as noinstr even though they should.

FWIW, this also means RCU_NONIDLE() is broken. Luckily there aren't many
users left.