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

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Date:   Tue, 8 Jun 2021 21:33:31 +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 6/8/21 7:39 PM, Steven Rostedt wrote:
>> 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?
>>
> Or perhaps have that pr_err() actually be written into the trace buffer?
> 
> You can use
> 
> 	trace_array_printk_buf(tr->array_buffer.buffer, _THIS_IP_, "string");
> 
> without it triggering that nasty trace_printk() notice ;-)

cool! I created a function osnoise_taint(char *msg) that prints the msg using
trace_array_printk_buf. I am using it instead of all pr_warn that could take
place inside osnoise regular operation.

I am still placing the note in the header, just in case we miss the message in
the log.

-- Daniel

> -- Steve
>