linux-kernel - Re: [RFC 1/3] softirq: Use preempt_latency

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Date:   Tue, 4 Jun 2019 12:39:03 +0200
From:   Daniel Bristot de Oliveira <bristot@...hat.com>
To:     Steven Rostedt <rostedt@...dmis.org>,
        Joel Fernandes <joel@...lfernandes.org>
Cc:     Daniel Bristot de Oliveira <bristot@...hat.com>,
        linux-kernel@...r.kernel.org, williams@...hat.com,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Matthias Kaehlcke <mka@...omium.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        Yangtao Li <tiny.windzz@...il.com>,
        Tommaso Cucinotta <tommaso.cucinotta@...tannapisa.it>
Subject: Re: [RFC 1/3] softirq: Use preempt_latency_stop/start to trace
 preemption



On 29/05/2019 14:22, Steven Rostedt wrote:
> On Wed, 29 May 2019 05:30:56 -0400
> Joel Fernandes <joel@...lfernandes.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
>