Re: [PATCH v3 08/22] rcu,tracing: Create trace_rcu_{enter,exit}()

[Peter Zijlstra]

On Wed, Feb 19, 2020 at 11:15:32AM -0500, Steven Rostedt wrote:
> On Wed, 19 Feb 2020 16:58:28 +0100
> Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> 
> > On Wed, Feb 19, 2020 at 10:49:03AM -0500, Steven Rostedt wrote:
> > > On Wed, 19 Feb 2020 15:47:32 +0100
> > > Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:  
> > 
> > > > These helpers are macros because of header-hell; they're placed here
> > > > because of the proximity to nmi_{enter,exit{().  
> > 
> > ^^^^
> 
> Bah I can't read, because I even went looking for this!
> 
> > 
> > > > +#define trace_rcu_enter()					\
> > > > +({								\
> > > > +	unsigned long state = 0;				\
> > > > +	if (!rcu_is_watching())	{				\
> > > > +		rcu_irq_enter_irqsave();			\
> > > > +		state = 1;					\
> > > > +	}							\
> > > > +	state;							\
> > > > +})
> > > > +
> > > > +#define trace_rcu_exit(state)					\
> > > > +do {								\
> > > > +	if (state)						\
> > > > +		rcu_irq_exit_irqsave();				\
> > > > +} while (0)
> > > > +  
> > > 
> > > Is there a reason that these can't be static __always_inline functions?  
> > 
> > It can be done, but then we need fwd declarations of those RCU functions
> > somewhere outside of rcupdate.h. It's all a bit of a mess.
> 
> Maybe this belongs in the rcupdate.h file then?

Possibly, and I suppose the current version is less obviously dependent
on the in_nmi() functionality as was the previous, seeing how Paul
frobbed that all the way into the rcu_irq_enter*() implementation.

So sure, I can go move it I suppose.