linux-kernel - Re: [PATCH RFC] tracepoint: Introduce tracepoint callbacks executing with preempt on

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Date:   Fri, 27 Apr 2018 12:46:41 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:     Joel Fernandes <joelaf@...gle.com>,
        LKML <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>,
        "Cc: Android Kernel" <kernel-team@...roid.com>
Subject: Re: [PATCH RFC] tracepoint: Introduce tracepoint callbacks
 executing with preempt on

On Fri, 27 Apr 2018 09:45:54 -0700
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> wrote:

> > > That shouldn't be needed. For the rcu_read_lock_sched case, there is a
> > > preempt_disable which needs to be a notrace, but for the srcu one,
> > > since we don't do that, I think it should be fine.  
> > 
> > Actually, I think I may agree here too. Because the _notrace is for
> > function tracing, and it shouldn't affect it. If people don't want it
> > traced, they could add those functions to the list in the notrace file.  
> 
> OK, feel free to ignore my notrace srcu_read_lock() patch, then.  ;-)

Of course I wasn't thinking about the lockdep tracepoints that Joel
mentioned, which happens to be the reason for all this discussion in
the first place :-)  Now I think we do need it. (OK, I can keep
changing my mind, can't I?).

-- Steve