linux-kernel - Re: [PATCH V3 8/9] tracing: Add osnoise tracer

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Message-ID: <abf38ca3-3c14-c00a-ff74-f1a75e3ec2e5@redhat.com>
Date:   Tue, 8 Jun 2021 19:17:55 +0200
From:   Daniel Bristot de Oliveira <bristot@...hat.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     linux-kernel@...r.kernel.org, Phil Auld <pauld@...hat.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Kate Carcia <kcarcia@...hat.com>,
        Jonathan Corbet <corbet@....net>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Alexandre Chartre <alexandre.chartre@...cle.com>,
        Clark Willaims <williams@...hat.com>,
        John Kacur <jkacur@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>, linux-doc@...r.kernel.org
Subject: Re: [PATCH V3 8/9] tracing: Add osnoise tracer

On 6/4/21 11:28 PM, Steven Rostedt wrote:
>> +	/*
>> +	 * This is an evidence of race conditions that cause
>> +	 * a value to be "discounted" too much.
>> +	 */
>> +	if (duration < 0)
>> +		pr_err("int safe negative!\n");
> Probably want to have this happen at most once a run. If something were
> to break, I don't think we want this to live lock the machine doing
> tons of prints. We could have a variable stored on the
> osnoise_variables that states this was printed. Check that variable to
> see if it wasn't printed during a run (when current_tracer was set),
> and print only once if it is.

I created a "bool tainted" variable, that is set true if any problem with time()
related functions happen. I will pr_warn that there is a problem on _start(),
but also print this info at the top of the tracer header, so it is clear also
from the trace output.

Thoughts?

-- Daniel