linux-kernel - Re: [PATCH 2/3] nohz: Convert tick dependency mask to atomic

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Date:	Fri, 25 Mar 2016 15:56:13 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 2/3] nohz: Convert tick dependency mask to atomic_t

On Fri, Mar 25, 2016 at 09:52:02AM +0100, Ingo Molnar wrote:
> > diff --git a/kernel/time/tick-sched.h b/kernel/time/tick-sched.h
> > index eb4e325..bf38226 100644
> > --- a/kernel/time/tick-sched.h
> > +++ b/kernel/time/tick-sched.h
> > @@ -60,7 +60,7 @@ struct tick_sched {
> >  	u64				next_timer;
> >  	ktime_t				idle_expires;
> >  	int				do_timer_last;
> > -	unsigned long			tick_dep_mask;
> > +	atomic_t			tick_dep_mask;
> >  };
> >  
> >  extern struct tick_sched *tick_get_tick_sched(int cpu);
> 
> Yeah, so I really like this interface, because it makes it really, really obvious 
> that only atomic_t-compatible operations can be used on the value. It's a common 
> bug to have a long, operated on atomically via bitops - and then occasionally 
> operated on in a non-atomic fashion, or used without taking ordering into account. 
> Such bugs are quite hard to find.
> 
> This change also shrinks the mask from long to int, which is an another bonus, and 
> which addresses the other objection Linus had.

Thanks, I much prefer it that way too!

Should I do a pull request or can I let you apply these?