Re: [RFC v1 2/2] rcu/tree: Remove dynticks_nmi_nesting counter

From: Joel Fernandes
Date: Thu Aug 29 2019 - 09:59:12 EST

On Wed, Aug 28, 2019 at 08:43:36PM -0700, Paul E. McKenney wrote:
> On the tracing patch... That patch might be a good idea regardless,
> but I bet that the reason that you felt the sudden need for it was due
> to the loss of information in your eventual ->dynticks_nesting field.
> After all, the value 0x1 might be an interrupt from idle, or it might
> just as easily be a task running in the kernel at process level.

True, however what really triggered me to do it was the existing code which
does not distinguish between entry/exit from USER and IDLE.

> The reason the patch might nevertheless be a good idea is that redundant
> information can be helpful when debugging. Especially when debugging
> new architecture-specific code, which is when RCU's dyntick-idle warnings
> tend to find bugs.

Sure, and also that it is more readable to ordinary human beings than "++="
and "--=" :-D.


- Joel