linux-kernel - Re: [RFC][PATCH 07/11] sched: Stop setting PREEMPT

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Message-ID: <20150929162504.GT3816@twins.programming.kicks-ass.net>
Date:	Tue, 29 Sep 2015 18:25:04 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	mingo@...nel.org, linux-kernel@...r.kernel.org,
	torvalds@...ux-foundation.org, fweisbec@...il.com, oleg@...hat.com,
	umgwanakikbuti@...il.com, tglx@...utronix.de
Subject: Re: [RFC][PATCH 07/11] sched: Stop setting PREEMPT_ACTIVE

On Tue, Sep 29, 2015 at 11:41:02AM -0400, Steven Rostedt wrote:
> On Tue, 29 Sep 2015 11:28:32 +0200
> Peter Zijlstra <peterz@...radead.org> wrote:
> 
> > Now that nothing tests for PREEMPT_ACTIVE anymore, stop setting it.
> > 
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> 
> 
> > @@ -3243,13 +3243,7 @@ asmlinkage __visible void __sched notrac
> >  		return;
> >  
> >  	do {
> > -		/*
> > -		 * Use raw __prempt_count() ops that don't call function.
> > -		 * We can't call functions before disabling preemption which
> > -		 * disarm preemption tracing recursions.
> > -		 */
> > -		__preempt_count_add(PREEMPT_ACTIVE + PREEMPT_DISABLE_OFFSET);
> > -		barrier();
> > +		preempt_disable_notrace();
> >  		/*
> >  		 * Needs preempt disabled in case user_exit() is traced
> >  		 * and the tracer calls preempt_enable_notrace() causing
> > @@ -3259,8 +3253,7 @@ asmlinkage __visible void __sched notrac
> >  		__schedule(true);
> >  		exception_exit(prev_ctx);
> >  
> > -		barrier();
> > -		__preempt_count_sub(PREEMPT_ACTIVE + PREEMPT_DISABLE_OFFSET);
> > +		preempt_enable_no_resched_notrace();
> 
> Nice, you used the notrace variants for this function.

There was a comment stating this was important, and its a notrace
annotated function :-)
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