Messages in this thread | | | Date | Thu, 28 Sep 2023 07:54:10 -0700 | From | Boqun Feng <> | Subject | Re: [RFC PATCH] srcu: Use try-lock lockdep annotation for NMI-safe access. |
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On Thu, Sep 28, 2023 at 10:09:00AM +0200, Peter Zijlstra wrote: > 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. >
Interesting
> Was this considered and intended? >
No, I don't think I have considered this before, I think I may still miss something here, maybe you or Paul can provide an example for such a case?
One thing though, before the commit, srcu_read_lock() already has an rcu_lock_acquire() annotation which eventually calls lock_acquire() which has a tracepoint in it.
Regards, Boqun
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