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

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Message-ID: <446AE5F2-39E0-46B6-8E0B-207E003DBF20@google.com>
Date:   Tue, 07 Aug 2018 10:10:59 -0400
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 August 7, 2018 9:49:54 AM EDT, Steven Rostedt <rostedt@...dmis.org> wrote:
>On Tue, 7 Aug 2018 06:33:35 -0700
>Joel Fernandes <joelaf@...gle.com> wrote:
>
>> 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,
>
>Interesting. I was following the old way where we called the tracing
>code before calling the lockdep code (all hard coded and not from
>trace events). Is this have something to do with calling the code from
>a tracepoint?
>
>Do you have an example that could trigger the warning?
>

I remember the warnings but can't remember now how I triggered them. I think I saw them with the irqsoff tracer or irq trace events running, with lockdep turned on.

Also an irq disable probe that does a lockdep assert that irqs are disabled could trigger it?

thanks,

- Joel


>-- Steve

-- 
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