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

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Message-ID: <20210609090329.53679e79@oasis.local.home>
Date:   Wed, 9 Jun 2021 09:03:29 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Daniel Bristot de Oliveira <bristot@...hat.com>
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 Wed, 9 Jun 2021 14:14:17 +0200
Daniel Bristot de Oliveira <bristot@...hat.com> wrote:

> On 6/4/21 11:28 PM, Steven Rostedt wrote:
> >> +#ifdef CONFIG_X86_LOCAL_APIC  
> > I wonder if we should move this into a separate file, making the
> > __trace_irq_entry() a more name space safe name and have it call that.
> > I have a bit of a distaste for arch specific code in a generic file.
> >   
> 
> I am placing the intel specific file in:
> 
> arch/x86/kernel/trace_osnoise.c

I would make it just arch/x86/kernel/trace.c

so that it can hold all arch specific tracing information, and not need
to create a file for anything else we might need later.

> 
> and the kernel/trace/trace_osnoise.h looks like this:
> 
> #ifdef CONFIG_X86_LOCAL_APIC
> int osnoise_arch_register(void);
> int osnoise_arch_unregister(void);
> #else /* CONFIG_X86_LOCAL_APIC */
> #define osnoise_arch_register() do {} while (0)
> #define osnoise_arch_unregister() do {} while (0)
> #endif /* CONFIG_X86_LOCAL_APIC */
> 
> This can be used by other archs as well...
> 
> sound reasonable?
> 

The proper way to d that is to use weak functions in the C code in the
generic file.

int __weak osnoise_arch_register(void)
{
	return 0;
}

int __weak osnoise_arch_unregister(void)
{
	return 0;
}

Hmm, does the unregister really need a return value?

-- Steve