* [PATCH] sched/rt: Fix rq's cpupri leak while enqueue/dequeue child RT entities
@ 2013-11-27 15:59 Kirill Tkhai
2013-12-12 10:30 ` Kirill Tkhai
2013-12-13 15:42 ` Peter Zijlstra
0 siblings, 2 replies; 6+ messages in thread
From: Kirill Tkhai @ 2013-11-27 15:59 UTC (permalink / raw)
To: linux-kernel@vger.kernel.org
Cc: Ingo Molnar, Peter Zijlstra, Steven Rostedt, stable
This patch touches RT group scheduling case.
Functions inc_rt_prio_smp() and dec_rt_prio_smp() change (global) rq's priority,
while rt_rq passed to them may be not the top-level rt_rq. This is wrong, because
changing of priority on a child level does not guarantee that the priority is
the highest all over the rq. So, this leak makes RT balancing unusable.
The short example: the task having the highest priority among all rq's RT tasks
(no one other task has the same priority) are waking on a throttle rt_rq.
The rq's cpupri is set to the task's priority equivalent, but real
rq->rt.highest_prio.curr is less.
The patch below fixes the problem.
It looks like all version have this bug, so I CC'ed stable mailing list.
Signed-off-by: Kirill Tkhai <tkhai@yandex.ru>
CC: Ingo Molnar <mingo@redhat.com>
CC: Peter Zijlstra <peterz@infradead.org>
CC: Steven Rostedt <rostedt@goodmis.org>
CC: stable@vger.kernel.org
---
kernel/sched/rt.c | 14 ++++++++++++++
1 files changed, 14 insertions(+), 0 deletions(-)
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 7d57275..1c40655 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -901,6 +901,13 @@ inc_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio)
{
struct rq *rq = rq_of_rt_rq(rt_rq);
+#ifdef CONFIG_RT_GROUP_SCHED
+ /*
+ * Change rq's cpupri only if rt_rq is the top queue.
+ */
+ if (&rq->rt != rt_rq)
+ return;
+#endif
if (rq->online && prio < prev_prio)
cpupri_set(&rq->rd->cpupri, rq->cpu, prio);
}
@@ -910,6 +917,13 @@ dec_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio)
{
struct rq *rq = rq_of_rt_rq(rt_rq);
+#ifdef CONFIG_RT_GROUP_SCHED
+ /*
+ * Change rq's cpupri only if rt_rq is the top queue.
+ */
+ if (&rq->rt != rt_rq)
+ return;
+#endif
if (rq->online && rt_rq->highest_prio.curr != prev_prio)
cpupri_set(&rq->rd->cpupri, rq->cpu, rt_rq->highest_prio.curr);
}
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] sched/rt: Fix rq's cpupri leak while enqueue/dequeue child RT entities
2013-11-27 15:59 [PATCH] sched/rt: Fix rq's cpupri leak while enqueue/dequeue child RT entities Kirill Tkhai
@ 2013-12-12 10:30 ` Kirill Tkhai
2013-12-13 15:42 ` Peter Zijlstra
1 sibling, 0 replies; 6+ messages in thread
From: Kirill Tkhai @ 2013-12-12 10:30 UTC (permalink / raw)
To: linux-kernel@vger.kernel.org
Cc: Ingo Molnar, Peter Zijlstra, Steven Rostedt,
stable@vger.kernel.org
Ping!
27.11.2013, 19:59, "Kirill Tkhai" <tkhai@yandex.ru>:
> This patch touches RT group scheduling case.
>
> Functions inc_rt_prio_smp() and dec_rt_prio_smp() change (global) rq's priority,
> while rt_rq passed to them may be not the top-level rt_rq. This is wrong, because
> changing of priority on a child level does not guarantee that the priority is
> the highest all over the rq. So, this leak makes RT balancing unusable.
>
> The short example: the task having the highest priority among all rq's RT tasks
> (no one other task has the same priority) are waking on a throttle rt_rq.
> The rq's cpupri is set to the task's priority equivalent, but real
> rq->rt.highest_prio.curr is less.
>
> The patch below fixes the problem.
>
> It looks like all version have this bug, so I CC'ed stable mailing list.
>
> Signed-off-by: Kirill Tkhai <tkhai@yandex.ru>
> CC: Ingo Molnar <mingo@redhat.com>
> CC: Peter Zijlstra <peterz@infradead.org>
> CC: Steven Rostedt <rostedt@goodmis.org>
> CC: stable@vger.kernel.org
>---
> kernel/sched/rt.c | 14 ++++++++++++++
> 1 files changed, 14 insertions(+), 0 deletions(-)
>diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
>index 7d57275..1c40655 100644
>--- a/kernel/sched/rt.c
>+++ b/kernel/sched/rt.c
>@@ -901,6 +901,13 @@ inc_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio)
> {
> struct rq *rq = rq_of_rt_rq(rt_rq);
>
>+#ifdef CONFIG_RT_GROUP_SCHED
>+ /*
>+ * Change rq's cpupri only if rt_rq is the top queue.
>+ */
>+ if (&rq->rt != rt_rq)
>+ return;
>+#endif
> if (rq->online && prio < prev_prio)
> cpupri_set(&rq->rd->cpupri, rq->cpu, prio);
> }
>@@ -910,6 +917,13 @@ dec_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio)
> {
> struct rq *rq = rq_of_rt_rq(rt_rq);
>
>+#ifdef CONFIG_RT_GROUP_SCHED
>+ /*
>+ * Change rq's cpupri only if rt_rq is the top queue.
>+ */
>+ if (&rq->rt != rt_rq)
>+ return;
>+#endif
> if (rq->online && rt_rq->highest_prio.curr != prev_prio)
> cpupri_set(&rq->rd->cpupri, rq->cpu, rt_rq->highest_prio.curr);
> }
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] sched/rt: Fix rq's cpupri leak while enqueue/dequeue child RT entities
2013-11-27 15:59 [PATCH] sched/rt: Fix rq's cpupri leak while enqueue/dequeue child RT entities Kirill Tkhai
2013-12-12 10:30 ` Kirill Tkhai
@ 2013-12-13 15:42 ` Peter Zijlstra
2013-12-17 12:02 ` Kirill Tkhai
1 sibling, 1 reply; 6+ messages in thread
From: Peter Zijlstra @ 2013-12-13 15:42 UTC (permalink / raw)
To: Kirill Tkhai
Cc: linux-kernel@vger.kernel.org, Ingo Molnar, Steven Rostedt, stable
On Wed, Nov 27, 2013 at 07:59:13PM +0400, Kirill Tkhai wrote:
> This patch touches RT group scheduling case.
>
> Functions inc_rt_prio_smp() and dec_rt_prio_smp() change (global) rq's priority,
> while rt_rq passed to them may be not the top-level rt_rq. This is wrong, because
> changing of priority on a child level does not guarantee that the priority is
> the highest all over the rq. So, this leak makes RT balancing unusable.
>
> The short example: the task having the highest priority among all rq's RT tasks
> (no one other task has the same priority) are waking on a throttle rt_rq.
> The rq's cpupri is set to the task's priority equivalent, but real
> rq->rt.highest_prio.curr is less.
>
> The patch below fixes the problem.
>
> It looks like all version have this bug, so I CC'ed stable mailing list.
Yeah, I think this is right.
cpupri stuff should indeed only be changed for the top level group.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] sched/rt: Fix rq's cpupri leak while enqueue/dequeue child RT entities
2013-12-13 15:42 ` Peter Zijlstra
@ 2013-12-17 12:02 ` Kirill Tkhai
2013-12-17 12:46 ` Peter Zijlstra
0 siblings, 1 reply; 6+ messages in thread
From: Kirill Tkhai @ 2013-12-17 12:02 UTC (permalink / raw)
To: Peter Zijlstra, Ingo Molnar
Cc: linux-kernel@vger.kernel.org, Steven Rostedt,
stable@vger.kernel.org
13.12.2013, 19:42, "Peter Zijlstra" <peterz@infradead.org>:
> On Wed, Nov 27, 2013 at 07:59:13PM +0400, Kirill Tkhai wrote:
>
>> О©╫This patch touches RT group scheduling case.
>>
>> О©╫Functions inc_rt_prio_smp() and dec_rt_prio_smp() change (global) rq's priority,
>> О©╫while rt_rq passed to them may be not the top-level rt_rq. This is wrong, because
>> О©╫changing of priority on a child level does not guarantee that the priority is
>> О©╫the highest all over the rq. So, this leak makes RT balancing unusable.
>>
>> О©╫The short example: the task having the highest priority among all rq's RT tasks
>> О©╫(no one other task has the same priority) are waking on a throttle rt_rq.
>> О©╫The rq's cpupri is set to the task's priority equivalent, but real
>> О©╫rq->rt.highest_prio.curr is less.
>>
>> О©╫The patch below fixes the problem.
>>
>> О©╫It looks like all version have this bug, so I CC'ed stable mailing list.
>
> Yeah, I think this is right.
>
> cpupri stuff should indeed only be changed for the top level group.
Ingo, are you going to apply this patch? Or will you give any comments?
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] sched/rt: Fix rq's cpupri leak while enqueue/dequeue child RT entities
2013-12-17 12:02 ` Kirill Tkhai
@ 2013-12-17 12:46 ` Peter Zijlstra
2013-12-17 13:08 ` Kirill Tkhai
0 siblings, 1 reply; 6+ messages in thread
From: Peter Zijlstra @ 2013-12-17 12:46 UTC (permalink / raw)
To: Kirill Tkhai
Cc: Ingo Molnar, linux-kernel@vger.kernel.org, Steven Rostedt,
stable@vger.kernel.org
On Tue, Dec 17, 2013 at 04:02:58PM +0400, Kirill Tkhai wrote:
>
>
> 13.12.2013, 19:42, "Peter Zijlstra" <peterz@infradead.org>:
> > On Wed, Nov 27, 2013 at 07:59:13PM +0400, Kirill Tkhai wrote:
> >
> >> �This patch touches RT group scheduling case.
> >>
> >> �Functions inc_rt_prio_smp() and dec_rt_prio_smp() change (global) rq's priority,
> >> �while rt_rq passed to them may be not the top-level rt_rq. This is wrong, because
> >> �changing of priority on a child level does not guarantee that the priority is
> >> �the highest all over the rq. So, this leak makes RT balancing unusable.
> >>
> >> �The short example: the task having the highest priority among all rq's RT tasks
> >> �(no one other task has the same priority) are waking on a throttle rt_rq.
> >> �The rq's cpupri is set to the task's priority equivalent, but real
> >> �rq->rt.highest_prio.curr is less.
> >>
> >> �The patch below fixes the problem.
> >>
> >> �It looks like all version have this bug, so I CC'ed stable mailing list.
> >
> > Yeah, I think this is right.
> >
> > cpupri stuff should indeed only be changed for the top level group.
>
> Ingo, are you going to apply this patch? Or will you give any comments?
I queued it, Ingo should get it through me somewhere today if all things
go well.
Thanks
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] sched/rt: Fix rq's cpupri leak while enqueue/dequeue child RT entities
2013-12-17 12:46 ` Peter Zijlstra
@ 2013-12-17 13:08 ` Kirill Tkhai
0 siblings, 0 replies; 6+ messages in thread
From: Kirill Tkhai @ 2013-12-17 13:08 UTC (permalink / raw)
To: Peter Zijlstra
Cc: Ingo Molnar, linux-kernel@vger.kernel.org, Steven Rostedt,
stable@vger.kernel.org
17.12.2013, 16:47, "Peter Zijlstra" <peterz@infradead.org>:
> On Tue, Dec 17, 2013 at 04:02:58PM +0400, Kirill Tkhai wrote:
>
>> О©╫13.12.2013, 19:42, "Peter Zijlstra" <peterz@infradead.org>:
>>> О©╫On Wed, Nov 27, 2013 at 07:59:13PM +0400, Kirill Tkhai wrote:
>>>> О©╫О©╫This patch touches RT group scheduling case.
>>>>
>>>> О©╫О©╫Functions inc_rt_prio_smp() and dec_rt_prio_smp() change (global) rq's priority,
>>>> О©╫О©╫while rt_rq passed to them may be not the top-level rt_rq. This is wrong, because
>>>> О©╫О©╫changing of priority on a child level does not guarantee that the priority is
>>>> О©╫О©╫the highest all over the rq. So, this leak makes RT balancing unusable.
>>>>
>>>> О©╫О©╫The short example: the task having the highest priority among all rq's RT tasks
>>>> О©╫О©╫(no one other task has the same priority) are waking on a throttle rt_rq.
>>>> О©╫О©╫The rq's cpupri is set to the task's priority equivalent, but real
>>>> О©╫О©╫rq->rt.highest_prio.curr is less.
>>>>
>>>> О©╫О©╫The patch below fixes the problem.
>>>>
>>>> О©╫О©╫It looks like all version have this bug, so I CC'ed stable mailing list.
>>> О©╫Yeah, I think this is right.
>>>
>>> О©╫cpupri stuff should indeed only be changed for the top level group.
>> О©╫Ingo, are you going to apply this patch? Or will you give any comments?
>
> I queued it, Ingo should get it through me somewhere today if all things
> go well.
>
> Thanks
Thanks, Peter
^ permalink raw reply [flat|nested] 6+ messages in thread
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2013-11-27 15:59 [PATCH] sched/rt: Fix rq's cpupri leak while enqueue/dequeue child RT entities Kirill Tkhai
2013-12-12 10:30 ` Kirill Tkhai
2013-12-13 15:42 ` Peter Zijlstra
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2013-12-17 13:08 ` Kirill Tkhai
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