Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Fri, 27 Apr 2018 10:00:48 -0700
From:   "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To:     Steven Rostedt <rostedt@goodmis.org>
Cc:     Joel Fernandes <joelaf@google.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Peter Zilstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        Tom Zanussi <tom.zanussi@linux.intel.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Thomas Glexiner <tglx@linutronix.de>,
        Boqun Feng <boqun.feng@gmail.com>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Randy Dunlap <rdunlap@infradead.org>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Fenguang Wu <fengguang.wu@intel.com>,
        Baohong Liu <baohong.liu@intel.com>,
        Vedang Patel <vedang.patel@intel.com>,
        "Cc: Android Kernel" <kernel-team@android.com>
Subject: Re: [PATCH RFC] tracepoint: Introduce tracepoint callbacks executing
 with preempt on
Reply-To: paulmck@linux.vnet.ibm.com
References: <20180427042656.190746-1-joelaf@google.com>
 <20180427155701.GL26088@linux.vnet.ibm.com>
 <CAJWu+or9GJwkDK9+842YbobG3=xVW-PgqS=uE5P2xFbDhmqxEQ@mail.gmail.com>
 <20180427122201.75abc313@gandalf.local.home>
 <20180427164554.GO26088@linux.vnet.ibm.com>
 <20180427124641.7b991c57@gandalf.local.home>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20180427124641.7b991c57@gandalf.local.home>
User-Agent: Mutt/1.5.21 (2010-09-15)
Message-Id: <20180427170048.GP26088@linux.vnet.ibm.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Fri, Apr 27, 2018 at 12:46:41PM -0400, Steven Rostedt wrote:
> On Fri, 27 Apr 2018 09:45:54 -0700
> "Paul E. McKenney" <paulmck@linux.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?).

You can, but at some point I start applying heavy-duty hysteresis.  ;-)

So the current thought (as of your having sent the above email) is that
we need notrace versions of srcu_read_lock() and srcu_read_unlock(),
but not for __srcu_read_lock() and __srcu_read_unlock(), correct?

							Thanx, Paul