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

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Message-Id: <20180427153826.GK26088@linux.vnet.ibm.com>
Date:   Fri, 27 Apr 2018 08:38:26 -0700
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Joel Fernandes <joelaf@...gle.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Tom Zanussi <tom.zanussi@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Boqun Feng <boqun.feng@...il.com>,
        fweisbec <fweisbec@...il.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        kbuild test robot <fengguang.wu@...el.com>,
        baohong liu <baohong.liu@...el.com>,
        vedang patel <vedang.patel@...el.com>, kernel-team@...roid.com
Subject: Re: [PATCH RFC] tracepoint: Introduce tracepoint callbacks executing
 with preempt on

On Fri, Apr 27, 2018 at 10:47:47AM -0400, Steven Rostedt wrote:
> On Fri, 27 Apr 2018 10:26:29 -0400 (EDT)
> Mathieu Desnoyers <mathieu.desnoyers@...icios.com> wrote:
> 
> > The general approach and the implementation look fine, except for
> > one small detail: I would be tempted to explicitly disable preemption
> > around the call to the tracepoint callback for the rcuidle variant,
> > unless we plan to audit every tracer right away to remove any assumption
> > that preemption is disabled in the callback implementation.
> 
> I'm thinking that we do that audit. There shouldn't be many instances
> of it. I like the idea that a tracepoint callback gets called with
> preemption enabled.

Are you really sure you want to increase your state space that much?

							Thanx, Paul