Re: [RFC PATCH] srcu: Use try-lock lockdep annotation for NMI-safe access.

Peter Zijlstra
2023-09-28T08:09:17Z

On Wed, Sep 27, 2023 at 11:06:09PM -0700, Boqun Feng wrote:

> I think this is a "side-effect" of commit f0f44752f5f6 ("rcu: Annotate
> SRCU's update-side lockdep dependencies"). In verify_lock_unused(), i.e.
> the checking for NMI lock usages, the logic is that

I think I'm having a problem with this commit -- that is, by adding
lockdep you're adding tracepoint, which rely on RCU being active.

The result is that SRCU is now no longer usable from !RCU regions.

Was this considered and intended?