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SubjectRE: [PATCH] sched/rt: don't enable runtime if already enabled
Ingo and All,

-----Original Message-----
From: Neil Zhang
Sent: 2012年12月4日 17:31
To: Neil Zhang; peterz@infradead.org; mingo@kernel.org
Cc: Chao Xie; linux-kernel@vger.kernel.org
Subject: RE: [PATCH] sched/rt: don't enable runtime if already enabled

Hi All,

-----Original Message-----
From: Neil Zhang [mailto:zhangwm@marvell.com]
Sent: 2012年12月3日 16:01
To: mingo@redhat.com; peterz@infradead.org
Cc: Chao Xie; linux-kernel@vger.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@marvell.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
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