linux-kernel - Re: [RFC PATCH 08/11] sched: Remove SD_WAKE_AFFINE flag and replace it with SD_BALANCE

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Date:	Thu, 23 Jun 2016 15:54:29 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Matt Fleming <matt@...eblueprint.co.uk>
Cc:	Yuyang Du <yuyang.du@...el.com>, mingo@...nel.org,
	linux-kernel@...r.kernel.org, umgwanakikbuti@...il.com,
	bsegall@...gle.com, pjt@...gle.com, morten.rasmussen@....com,
	vincent.guittot@...aro.org, dietmar.eggemann@....com
Subject: Re: [RFC PATCH 08/11] sched: Remove SD_WAKE_AFFINE flag and replace
 it with SD_BALANCE_WAKE

On Thu, Jun 23, 2016 at 02:04:33PM +0100, Matt Fleming wrote:
> On Thu, 16 Jun, at 09:49:32AM, Yuyang Du wrote:
> > --- a/include/linux/sched.h
> > +++ b/include/linux/sched.h
> > @@ -1014,7 +1014,6 @@ extern void wake_up_q(struct wake_q_head *head);
> >  #define SD_BALANCE_EXEC		0x0004	/* Balance on exec */
> >  #define SD_BALANCE_FORK		0x0008	/* Balance on fork, clone */
> >  #define SD_BALANCE_WAKE		0x0010  /* Balance on wakeup */
> > -#define SD_WAKE_AFFINE		0x0020	/* Wake task to waking CPU */
> >  #define SD_SHARE_CPUCAPACITY	0x0080	/* Domain members share cpu power */
> >  #define SD_SHARE_POWERDOMAIN	0x0100	/* Domain members share power domain */
> >  #define SD_SHARE_PKG_RESOURCES	0x0200	/* Domain members share cpu pkg resources */
> 
> I'm curious - doesn't this break userspace ABI? These flags are
> exported via procfs, so I would have assumed removing or changing the
> value of any of these constants would be forbidden.

Generally I ignore this little issue. Also, I suppose we should move
that whole sched_domain cruft into /debug/sched/ or so.