linux-kernel - Re: [RFC][PATCH 3/5] sched: Change the ttwu success details

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Date:	Thu, 16 Dec 2010 16:45:35 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Chris Mason <chris.mason@...cle.com>,
	Frank Rowand <frank.rowand@...sony.com>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Mike Galbraith <efault@....de>,
	Oleg Nesterov <oleg@...hat.com>, Paul Turner <pjt@...gle.com>,
	Jens Axboe <axboe@...nel.dk>, linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH 3/5] sched: Change the ttwu success details

On Thu, Dec 16, 2010 at 04:30:15PM +0100, Peter Zijlstra wrote:
> On Thu, 2010-12-16 at 16:27 +0100, Peter Zijlstra wrote:
> > On Thu, 2010-12-16 at 16:23 +0100, Frederic Weisbecker wrote:
> > 
> > > > -	TP_printk("comm=%s pid=%d prio=%d success=%d target_cpu=%03d",
> > > > +	TP_printk("comm=%s pid=%d prio=%d target_cpu=%03d",
> > > >  		  __entry->comm, __entry->pid, __entry->prio,
> > > > -		  __entry->success, __entry->target_cpu)
> > > > +		  __entry->target_cpu)
> > > 
> > > Note we'll need to fix some perf scripts after that. And also perf sched,
> > > probably perf timechart and so on...
> > 
> > Do any of those actually use the success parameter? If not, then me
> > removing it shouldn't break those tools since they're supposed to parse
> > the format stuff and not notice it missing ;-)
> 
> Alternatively we could always call trace_sched_wakeup() and make success
> reflect actual wakeup success.

So, that would work very well for sched-migration.py

builtin-sched.c would continue to work fine but would notice that as
a bug if a wake up occur on a task already running.

But it will only trigger a warning, besides that it will just continue
to work normally.

It's ok I think, if that old tool triggers a spurious warning. I suspect
very few people use it anyway.
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