linux-kernel - Re: [PATCH RFC v5 3/6] srcu: Add notrace variant of srcu

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Date:   Tue, 1 May 2018 08:27:43 -0700
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Joel Fernandes <joelaf@...gle.com>, linux-kernel@...r.kernel.org,
        Peter Zilstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Tom Zanussi <tom.zanussi@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Thomas Glexiner <tglx@...utronix.de>,
        Boqun Feng <boqun.feng@...il.com>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Fenguang Wu <fengguang.wu@...el.com>,
        Baohong Liu <baohong.liu@...el.com>,
        Vedang Patel <vedang.patel@...el.com>, kernel-team@...roid.com
Subject: Re: [PATCH RFC v5 3/6] srcu: Add notrace variant of srcu_dereference

On Tue, May 01, 2018 at 11:04:03AM -0400, Steven Rostedt wrote:
> On Tue, 1 May 2018 07:18:17 -0700
> "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> wrote:
> 
> 
> > > diff --git a/include/linux/srcu.h b/include/linux/srcu.h
> > > index 2ec618979b20..a1c4947be877 100644
> > > --- a/include/linux/srcu.h
> > > +++ b/include/linux/srcu.h
> > > @@ -135,6 +135,11 @@ static inline int srcu_read_lock_held(const struct srcu_struct *sp)
> > >   */
> > >  #define srcu_dereference(p, sp) srcu_dereference_check((p), (sp), 0)
> > > 
> > > +/**
> > > + * srcu_dereference_notrace - no tracing and no lockdep calls from here
> > > + */
> > > +#define srcu_dereference_notrace(p, sp) srcu_dereference_check((p), (sp), 1)  
> > 
> > Given that this is a one-liner, why not just use srcu_dereference_check()
> > directly, with 1 as you do above to disable lockdep?
> 
> I prefer what Joel did. It documents why we are doing this. Open coding
> the call directly will just confuse others that touch tracepoint code.

I suppose...

Reviewed-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>