Re: [PATCH net-next] rcu: prevent RCU_LOCKDEP_WARN() from swallowing the condition

On Mon, Sep 14, 2020 at 05:30:29PM -0700, Jakub Kicinski wrote:

On Mon, 14 Sep 2020 17:20:11 -0700 Paul E. McKenney wrote:

quoted

quoted

Seems like quite a few places depend on the macro disappearing its
argument. I was concerned that it's going to be had to pick out whether
!LOCKDEP builds should return true or false from LOCKDEP helpers, but
perhaps relying on the linker errors even more is not such poor taste?

Does the patch below look acceptable to you?  

The thing to check would be whether all compilers do sufficient
dead-code elimination (it used to be that they did not).  One way to
get a quick sniff test of this would be to make sure that a dead-code
lockdep_is_held() is in common code, and then expose this patch to kbuild
test robot.

I'm pretty sure it's in common code because kbuild bot complaints were
the reason I gave up the first time around ;) 

I'll expose this to kbuild bot via my kernel.org tree in case it
doesn't consider scissored patches and report back!

Sounds good, thank you!

							Thanx, Paul