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Date:   Thu, 13 Feb 2020 09:28:14 +0100
From:   Peter Zijlstra <peterz@infradead.org>
To:     Joel Fernandes <joel@joelfernandes.org>
Cc:     linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
        rostedt@goodmis.org, mingo@kernel.org, gregkh@linuxfoundation.org,
        gustavo@embeddedor.com, tglx@linutronix.de, paulmck@kernel.org,
        josh@joshtriplett.org, mathieu.desnoyers@efficios.com,
        jiangshanlai@gmail.com
Subject: Re: [PATCH v2 3/9] rcu,tracing: Create trace_rcu_{enter,exit}()
Message-ID: <20200213082814.GJ14897@hirez.programming.kicks-ass.net>
References: <20200212210139.382424693@infradead.org>
 <20200212210749.971717428@infradead.org>
 <20200212232702.GA170680@google.com>
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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.