linux-kernel - Re: [PATCH v12 3/3] tracing: Centralize preemptirq tracepoints and unify their usage

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Date:   Tue, 7 Aug 2018 20:48:20 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Joel Fernandes <joelaf@...gle.com>
Cc:     Joel Fernandes <joel@...lfernandes.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "Cc: Android Kernel" <kernel-team@...roid.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Byungchul Park <byungchul.park@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Paul McKenney <paulmck@...ux.vnet.ibm.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Glexiner <tglx@...utronix.de>,
        Tom Zanussi <tom.zanussi@...ux.intel.com>
Subject: Re: [PATCH v12 3/3] tracing: Centralize preemptirq tracepoints and
 unify their usage

On Tue, 07 Aug 2018 19:54:13 -0400
Joel Fernandes <joelaf@...gle.com> wrote:


> >OK, I hit this bug, but it's not because of the partial revert. This
> >bug seems it needs to be another partial revert. I like you movement of
> >the code, but I'm starting to doubt that we can use a trace event as a
> >hook for critical areas yet. Well, not until we can use srcu in NMI.
> >  
> 
> I sent a patch to use srcu for all tracepoints including nmi. That
> patch also removes this warning and fixes the one other issue masami
> reported (hot plug causing a warning).

Is it one I can take, or does Paul have it? I'll need it to continue
with this as is, because I can't pass my tests without triggering that
warning (and that fails the test).

> 
> If Paul and Mathieu can confirm SRCU works on offline CPUs that would
> be great.

Yes please.

> 
> It's just this one warning or anything else that makes you feel
> tracepoints for critical paths isn't feasible?

Currently I'm down to this, but I can't get past my first test in my
ktest suite, because it fails here.

-- Steve