linux-kernel - RE: [PATCH] sched/rt: don't enable runtime if already enabled

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Date:	Fri, 28 Dec 2012 02:01:10 -0800
From:	Neil Zhang <zhangwm@...vell.com>
To:	Mike Galbraith <bitbucket@...ine.de>
CC:	"peterz@...radead.org" <peterz@...radead.org>,
	"mingo@...nel.org" <mingo@...nel.org>,
	Chao Xie <cxie4@...vell.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] sched/rt: don't enable runtime if already enabled

Mike,

> -----Original Message-----
> From: Mike Galbraith [mailto:bitbucket@...ine.de]
> Sent: 2012年12月12日 17:39
> To: Neil Zhang
> Cc: peterz@...radead.org; mingo@...nel.org; Chao Xie;
> linux-kernel@...r.kernel.org
> Subject: RE: [PATCH] sched/rt: don't enable runtime if already enabled
> 
> On Tue, 2012-12-11 at 21:38 -0800, Neil Zhang wrote:
> > Ingo and All,
> 
> Hm, /me wonders why we would even need update_runtime() handler.  We
> disable at CPU_DOWN_PREPARE in update_runtime(), again at CPU_DYING
> in migration_call(), and enable at CPU_ONLINE in both.
> 
Totally agree with you.
Then I will prepare another patch to remove it.
Thanks.

> > -----Original Message-----
> > From: Neil Zhang
> > Sent: 2012年12月4日 17:31
> > To: Neil Zhang; peterz@...radead.org; mingo@...nel.org
> > Cc: Chao Xie; linux-kernel@...r.kernel.org
> > Subject: RE: [PATCH] sched/rt: don't enable runtime if already enabled
> >
> > Hi All,
> >
> > -----Original Message-----
> > From: Neil Zhang [mailto:zhangwm@...vell.com]
> > Sent: 2012年12月3日 16:01
> > To: mingo@...hat.com; peterz@...radead.org
> > Cc: Chao Xie; linux-kernel@...r.kernel.org; Neil Zhang
> > Subject: [PATCH] sched/rt: don't enable runtime if already enabled
> >
> > There are two paths will call __enable_runtime, they are enable_runtime
> and rq_online. Don't enable runtime again if it is already enabled.
> > It can fix the following kernel BUG when do cpu hotplug while there are
> realtime threads running.
> >
> > [ 3347.091644] kernel BUG at kernel/sched/rt.c:687!
> > [ 3347.091674] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM
> [ 3347.091674] Modules linked in: cidatattydev(O) gs_diag(O) diag(O)
> gs_modem(O) ccinetdev(O) cci_datastub(O) citty(O) msocke
> > [ 3347.091705] CPU: 1    Tainted: G           O  (3.4.5+ #439)
> > [ 3347.091735] PC is at __disable_runtime+0x1e4/0x240 [ 3347.091735] LR
> is at __disable_runtime+0x1dc/0x240
> > [ 3347.091735] pc : [<c0162124>]    lr : [<c016211c>]    psr:
> > 	a0000093
> > [ 3347.091735] sp : e0061dc8  ip : c0807861  fp : c07a9740 [
> > 3347.091766] r10: c1a0b740  r9 : ffffffff  r8 : fd050f80 [
> > 3347.091766] r7 : 00000002  r6 : 000003f8  r5 : c1a13740  r4 :
> > c1a137d8 [ 3347.091766] r3 : ffffffff  r2 : e0061dbc  r1 : c06b11b6
> > r0 : 00000037 [ 3347.091796] Flags: NzCv  IRQs off  FIQs on  Mode
> > SVC_32  ISA ARM  Segment kernel [ 3347.091796] Control: 10c53c7d
> > Table: 21e5004a  DAC: 00000015
> >
> > Signed-off-by: Neil Zhang <zhangwm@...vell.com>
> > ---
> >  kernel/sched/rt.c |    8 +++++---
> >  1 files changed, 5 insertions(+), 3 deletions(-)
> >
> > diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index
> > 418feb0..6525e5b 100644
> > --- a/kernel/sched/rt.c
> > +++ b/kernel/sched/rt.c
> > @@ -722,9 +722,11 @@ static void __enable_runtime(struct rq *rq)
> >
> >  		raw_spin_lock(&rt_b->rt_runtime_lock);
> >  		raw_spin_lock(&rt_rq->rt_runtime_lock);
> > -		rt_rq->rt_runtime = rt_b->rt_runtime;
> > -		rt_rq->rt_time = 0;
> > -		rt_rq->rt_throttled = 0;
> > +		if (rt_rq->rt_runtime == RUNTIME_INF) {
> > +			rt_rq->rt_runtime = rt_b->rt_runtime;
> > +			rt_rq->rt_time = 0;
> > +			rt_rq->rt_throttled = 0;
> > +		}
> >  		raw_spin_unlock(&rt_rq->rt_runtime_lock);
> >  		raw_spin_unlock(&rt_b->rt_runtime_lock);
> >  	}
> > --
> > 1.7.4.1
> >
> > Ingo seems use another mail now, update the To list.
> >
> > Best Regards,
> > Neil Zhang
> >
> > Please help review it.
> >
> > Best Regards,
> > Neil Zhang
> > NР骒rybX肚v^)藓{.n+伐{赙zXФ≤}财z&j:+v赙zZ++zf＂h~izwア?ㄨ&)
> 撷f^j谦ym@Aa囤0鹅hi
> 

Best Regards,
Neil Zhang