linux-kernel - Re: [PATCH] tracing/perf: Move rcu_irq_enter/exit

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Date:   Tue, 11 Feb 2020 09:10:40 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        "Joel Fernandes (Google)" <joel@...lfernandes.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Josh Triplett <josh@...htriplett.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>
Subject: Re: [PATCH] tracing/perf: Move rcu_irq_enter/exit_irqson() to perf
 trace point hook

On Tue, 11 Feb 2020 13:21:20 +0100
Peter Zijlstra <peterz@...radead.org> wrote:

> > @@ -68,6 +78,9 @@ perf_trace_##call(void *__data, proto)					\
> >  	perf_trace_run_bpf_submit(entry, __entry_size, rctx,		\
> >  				  event_call, __count, __regs,		\
> >  				  head, __task);			\
> > +out:									\
> > +	if (!rcu_watching)						\
> > +		rcu_irq_exit_irqson();					\
> >  }  
> 
> It is probably okay to move that into perf_tp_event(), then this:
> 
> >  /*
> > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> > index 1694a6b57ad8..3e6f07b62515 100644
> > --- a/kernel/rcu/tree.c
> > +++ b/kernel/rcu/tree.c
> > @@ -719,6 +719,7 @@ void rcu_irq_exit_irqson(void)
> >  	rcu_irq_exit();
> >  	local_irq_restore(flags);
> >  }
> > +EXPORT_SYMBOL_GPL(rcu_irq_exit_irqson);
> >  
> >  /*
> >   * Exit an RCU extended quiescent state, which can be either the
> > @@ -890,6 +891,7 @@ void rcu_irq_enter_irqson(void)
> >  	rcu_irq_enter();
> >  	local_irq_restore(flags);
> >  }
> > +EXPORT_SYMBOL_GPL(rcu_irq_enter_irqson);
> >  
> >  /*
> >   * If any sort of urgency was applied to the current CPU (for example,  
> 
> can go too. Those things really should not be exported.

Thanks, I'll send an updated patch.

-- Steve