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

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Message-Id: <1354521675-31245-1-git-send-email-zhangwm@marvell.com>
Date:	Mon,  3 Dec 2012 16:01:15 +0800
From:	Neil Zhang <zhangwm@...vell.com>
To:	mingo@...hat.com, peterz@...radead.org
Cc:	cxie4@...vell.com, linux-kernel@...r.kernel.org,
	Neil Zhang <zhangwm@...vell.com>
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

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