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Date: Thu, 16 Dec 2010 16:45:35 +0100
From: Frederic Weisbecker <fweisbec@gmail.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Chris Mason <chris.mason@oracle.com>,
        Frank Rowand <frank.rowand@am.sony.com>, Ingo Molnar <mingo@elte.hu>,
        Thomas Gleixner <tglx@linutronix.de>, Mike Galbraith <efault@gmx.de>,
        Oleg Nesterov <oleg@redhat.com>, Paul Turner <pjt@google.com>,
        Jens Axboe <axboe@kernel.dk>, linux-kernel@vger.kernel.org
Subject: Re: [RFC][PATCH 3/5] sched: Change the ttwu success details
Message-ID: <20101216154533.GE1687@nowhere>
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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.