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Subject: Re: [RFC 1/3] softirq: Use preempt_latency_stop/start to trace
 preemption
To:     Steven Rostedt <rostedt@goodmis.org>,
        Joel Fernandes <joel@joelfernandes.org>
Cc:     Daniel Bristot de Oliveira <bristot@redhat.com>,
        linux-kernel@vger.kernel.org, williams@redhat.com,
        Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Matthias Kaehlcke <mka@chromium.org>,
        Frederic Weisbecker <frederic@kernel.org>,
        Yangtao Li <tiny.windzz@gmail.com>,
        Tommaso Cucinotta <tommaso.cucinotta@santannapisa.it>
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 <20190529093056.GA146079@google.com>
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From:   Daniel Bristot de Oliveira <bristot@redhat.com>
Message-ID: <835664be-a8ef-d164-4bf9-e0918413796c@redhat.com>
Date:   Tue, 4 Jun 2019 12:39:03 +0200
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On 29/05/2019 14:22, Steven Rostedt wrote:
> On Wed, 29 May 2019 05:30:56 -0400
> Joel Fernandes <joel@joelfernandes.org> wrote:
> 
>> Yes, I think so. Also this patch changes CALLER_ADDR0 passed to the
>> tracepoint because there's one more level of a non-inlined function call
>> in the call chain right?  Very least the changelog should document this
>> change in functional behavior, IMO.

In practice I am seeing no change in the values printed, but there is another
problem with this regard: there are cases in which both caller and parent have
the same address.

I am quite sure it has to do with the in_lock_function() behavior. Anyway, I was
already planing to propose a cleanup in the in_lock_function/in_sched_function.
I will investigate it more.

> This sounds more like a break in behavior not a functional change. I
> guess moving it to a header and making it a static __always_inline
> should be fine though.

Steve, which header should I use?

Thanks!

-- Daniel

> -- Steve
>