Re: [PATCH v2 3/9] rcu,tracing: Create trace_rcu_{enter,exit}()

[Peter Zijlstra]

On Wed, Feb 12, 2020 at 06:27:02PM -0500, Joel Fernandes wrote:
> On Wed, Feb 12, 2020 at 10:01:42PM +0100, Peter Zijlstra wrote:

> > +#define trace_rcu_enter()					\
> > +({								\
> > +	unsigned long state = 0;				\
> > +	if (!rcu_is_watching())	{				\
> > +		if (in_nmi()) {					\
> > +			state = __TR_NMI;			\
> > +			rcu_nmi_enter();			\
> > +		} else {					\
> > +			state = __TR_IRQ;			\
> > +			rcu_irq_enter_irqsave();		\
> 
> Since rcu_irq_enter_irqsave can be called from a tracer context, should those
> be marked with notrace as well? AFAICS, there's no notrace marking on them.

It should work, these functions are re-entrant (as are IRQs / NMIs) and
Steve wants to be able to trace RCU itself.