linux-kernel - Re: [PATCH v9 5/7] tracing: Centralize preemptirq tracepoints and unify their usage

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Date:   Thu, 12 Jul 2018 09:37:47 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Joel Fernandes <joel@...lfernandes.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        linux-kernel@...r.kernel.org, Boqun Feng <boqun.feng@...il.com>,
        Byungchul Park <byungchul.park@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Julia Cartwright <julia@...com>,
        linux-kselftest@...r.kernel.org,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Paul McKenney <paulmck@...ux.vnet.ibm.com>,
        Thomas Glexiner <tglx@...utronix.de>,
        Tom Zanussi <tom.zanussi@...ux.intel.com>,
        kernel-team@...roid.com
Subject: Re: [PATCH v9 5/7] tracing: Centralize preemptirq tracepoints and
 unify their usage

On Thu, 12 Jul 2018 01:38:05 -0700
Joel Fernandes <joel@...lfernandes.org> wrote:

> So actually with or without the clean up, I don't see any issues with
> dropping lockdep_recursing in my tests at the moment. I'm not sure something
> else changed between then and now causing the issue to go away. I can include
> Peter's clean up in my series though if he's Ok with it since you guys agree
> its a good clean up anyway. Would you prefer I did that, and then also
> dropped the lockdep_recursing checks? Or should I keep the
> lockdep_recursing() checks just to be safe? Do you see cases where you want
> irqsoff tracing while lockdep_recursing() is true?

I say rewrite it as per Peter's suggestion. Perhaps even add credit to
Peter like:

Cleaned-up-code-by: Peter Zijlstra <peterz@...radead.org>

  ;-)

And yes, I would recommend dropping the lockdep_recursion() if you
can't trigger issues from within your tests. If it shows up later, we
can always add it back.

Thanks!

-- Steve