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

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Date:   Tue, 7 Aug 2018 06:33:35 -0700
From:   Joel Fernandes <joelaf@...gle.com>
To:     Steven Rostedt <rostedt@...dmis.org>
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 Mon, Aug 6, 2018 at 6:43 PM, Steven Rostedt <rostedt@...dmis.org> wrote:
> On Mon, 6 Aug 2018 17:43:19 -0700
> Joel Fernandes <joelaf@...gle.com> wrote:
>
>> On Mon, Aug 6, 2018 at 12:50 PM, Steven Rostedt <rostedt@...dmis.org> wrote:
>> >
>> > With this patch applied, I'm constantly getting lockdep errors. Instead
>> > of doing a full revert of the patch, I did this, which makes all those
>> > errors go away. I may apply this for now, and we can revisit having
>> > lockdep use the tracepoint code. But since it's currently always
>> > enabled, I'm thinking of just leaving this as is. The macros are still
>> > clean from Joel's patch.
>> >
>> > Thoughts?
>>
>> I like your patch. Thanks a lot for doing this.. It keeps most of the
>> benefits of my patch while avoiding the issues with lockdep. I agree
>> we can look at the remaining lockdep issue after. There were several
>> lockdep issues with this patch that I fixed over the the months, but
>> there's still the one that Masami reported that I believe you're also
>> seeing. Once I'm back I'll work on figuring that one out.
>>
>> Could you pull in the fixes to the other issues I posted though? With
>> that we should be good.
>> https://lore.kernel.org/patchwork/patch/971104/
>> https://lore.kernel.org/patchwork/patch/971829/
>>
>
> I already had these applied when I created this patch ;-)
>
> Thanks, I'll add it.

Thanks, also one more thing I noticed in your patch,
lockdep_hardirqs_off needs to be called before all other probes but
you're calling it after. This is why I registered it with INT_MAX:

register_trace_prio_irq_disable(lockdep_hardirqs_off, NULL, INT_MAX);

Without it you may get annotation warnings. Thanks,

- Joel