[PATCH] sched/deadline: stop dl_server before CPU goes offline

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* [PATCH] sched/deadline: stop dl_server before CPU goes offline
@ 2025-10-09 18:47 ` Shrikanth Hegde
  2025-10-09 20:28   ` Marek Szyprowski
                     ` (3 more replies)
  0 siblings, 4 replies; 7+ messages in thread
From: Shrikanth Hegde @ 2025-10-09 18:47 UTC (permalink / raw)
  To: peterz, juri.lelli
  Cc: sshegde, mingo, vincent.guittot, linux-kernel, linuxppc-dev,
	m.szyprowski, venkat88, jstultz

From: Peter Zijlstra (Intel) <peterz@infradead.org>

IBM CI tool reported kernel warning[1] when running a CPU removal
operation through drmgr[2]. i.e "drmgr -c cpu -r -q 1"

WARNING: CPU: 0 PID: 0 at kernel/sched/cpudeadline.c:219 cpudl_set+0x58/0x170
NIP [c0000000002b6ed8] cpudl_set+0x58/0x170
LR [c0000000002b7cb8] dl_server_timer+0x168/0x2a0
Call Trace:
[c000000002c2f8c0] init_stack+0x78c0/0x8000 (unreliable)
[c0000000002b7cb8] dl_server_timer+0x168/0x2a0
[c00000000034df84] __hrtimer_run_queues+0x1a4/0x390
[c00000000034f624] hrtimer_interrupt+0x124/0x300
[c00000000002a230] timer_interrupt+0x140/0x320

Git bisects to: commit 4ae8d9aa9f9d ("sched/deadline: Fix dl_server getting stuck")

This happens since: 
- dl_server hrtimer gets enqueued close to cpu offline, when 
  kthread_park enqueues a fair task.
- CPU goes offline and drmgr removes it from cpu_present_mask.
- hrtimer fires and warning is hit.

Fix it by stopping the dl_server before CPU is marked dead.

[1]: https://lore.kernel.org/all/8218e149-7718-4432-9312-f97297c352b9@linux.ibm.com/
[2]: https://github.com/ibm-power-utilities/powerpc-utils/tree/next/src/drmgr

[sshegde: wrote the changelog and tested it]
Fixes: 4ae8d9aa9f9d ("sched/deadline: Fix dl_server getting stuck")
Reported-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
Closes: https://lore.kernel.org/all/8218e149-7718-4432-9312-f97297c352b9@linux.ibm.com
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Shrikanth Hegde <sshegde@linux.ibm.com>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Tested-by: Shrikanth Hegde <sshegde@linux.ibm.com>
---
 kernel/sched/core.c     | 2 ++
 kernel/sched/deadline.c | 3 +++
 2 files changed, 5 insertions(+)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 198d2dd45f59..f1ebf67b48e2 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -8571,10 +8571,12 @@ int sched_cpu_dying(unsigned int cpu)
 	sched_tick_stop(cpu);
 
 	rq_lock_irqsave(rq, &rf);
+	update_rq_clock(rq);
 	if (rq->nr_running != 1 || rq_has_pinned_tasks(rq)) {
 		WARN(true, "Dying CPU not properly vacated!");
 		dump_rq_tasks(rq, KERN_WARNING);
 	}
+	dl_server_stop(&rq->fair_server);
 	rq_unlock_irqrestore(rq, &rf);
 
 	calc_load_migrate(rq);
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 615411a0a881..7b7671060bf9 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1582,6 +1582,9 @@ void dl_server_start(struct sched_dl_entity *dl_se)
 	if (!dl_server(dl_se) || dl_se->dl_server_active)
 		return;
 
+	if (WARN_ON_ONCE(!cpu_online(cpu_of(rq))))
+		return;
+
 	dl_se->dl_server_active = 1;
 	enqueue_dl_entity(dl_se, ENQUEUE_WAKEUP);
 	if (!dl_task(dl_se->rq->curr) || dl_entity_preempt(dl_se, &rq->curr->dl))
-- 
2.47.3



^ permalink raw reply related	[flat|nested] 7+ messages in thread

* Re: [PATCH] sched/deadline: stop dl_server before CPU goes offline
  2025-10-09 18:47 ` [PATCH] sched/deadline: stop dl_server before CPU goes offline Shrikanth Hegde
@ 2025-10-09 20:28   ` Marek Szyprowski
  2025-10-10  4:59   ` Venkat
                     ` (2 subsequent siblings)
  3 siblings, 0 replies; 7+ messages in thread
From: Marek Szyprowski @ 2025-10-09 20:28 UTC (permalink / raw)
  To: Shrikanth Hegde, peterz, juri.lelli
  Cc: mingo, vincent.guittot, linux-kernel, linuxppc-dev, venkat88,
	jstultz

On 09.10.2025 20:47, Shrikanth Hegde wrote:
> From: Peter Zijlstra (Intel) <peterz@infradead.org>
>
> IBM CI tool reported kernel warning[1] when running a CPU removal
> operation through drmgr[2]. i.e "drmgr -c cpu -r -q 1"
>
> WARNING: CPU: 0 PID: 0 at kernel/sched/cpudeadline.c:219 cpudl_set+0x58/0x170
> NIP [c0000000002b6ed8] cpudl_set+0x58/0x170
> LR [c0000000002b7cb8] dl_server_timer+0x168/0x2a0
> Call Trace:
> [c000000002c2f8c0] init_stack+0x78c0/0x8000 (unreliable)
> [c0000000002b7cb8] dl_server_timer+0x168/0x2a0
> [c00000000034df84] __hrtimer_run_queues+0x1a4/0x390
> [c00000000034f624] hrtimer_interrupt+0x124/0x300
> [c00000000002a230] timer_interrupt+0x140/0x320
>
> Git bisects to: commit 4ae8d9aa9f9d ("sched/deadline: Fix dl_server getting stuck")
>
> This happens since:
> - dl_server hrtimer gets enqueued close to cpu offline, when
>    kthread_park enqueues a fair task.
> - CPU goes offline and drmgr removes it from cpu_present_mask.
> - hrtimer fires and warning is hit.
>
> Fix it by stopping the dl_server before CPU is marked dead.
>
> [1]: https://lore.kernel.org/all/8218e149-7718-4432-9312-f97297c352b9@linux.ibm.com/
> [2]: https://github.com/ibm-power-utilities/powerpc-utils/tree/next/src/drmgr
>
> [sshegde: wrote the changelog and tested it]
> Fixes: 4ae8d9aa9f9d ("sched/deadline: Fix dl_server getting stuck")
> Reported-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
> Closes: https://lore.kernel.org/all/8218e149-7718-4432-9312-f97297c352b9@linux.ibm.com
Closes: 
https://lore.kernel.org/all/e56310b5-f7a9-4fad-b79a-dcbcdd3d3883@samsung.com/
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> Signed-off-by: Shrikanth Hegde <sshegde@linux.ibm.com>
> Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
> Tested-by: Shrikanth Hegde <sshegde@linux.ibm.com>
> ---
>   kernel/sched/core.c     | 2 ++
>   kernel/sched/deadline.c | 3 +++
>   2 files changed, 5 insertions(+)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 198d2dd45f59..f1ebf67b48e2 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -8571,10 +8571,12 @@ int sched_cpu_dying(unsigned int cpu)
>   	sched_tick_stop(cpu);
>   
>   	rq_lock_irqsave(rq, &rf);
> +	update_rq_clock(rq);
>   	if (rq->nr_running != 1 || rq_has_pinned_tasks(rq)) {
>   		WARN(true, "Dying CPU not properly vacated!");
>   		dump_rq_tasks(rq, KERN_WARNING);
>   	}
> +	dl_server_stop(&rq->fair_server);
>   	rq_unlock_irqrestore(rq, &rf);
>   
>   	calc_load_migrate(rq);
> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> index 615411a0a881..7b7671060bf9 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -1582,6 +1582,9 @@ void dl_server_start(struct sched_dl_entity *dl_se)
>   	if (!dl_server(dl_se) || dl_se->dl_server_active)
>   		return;
>   
> +	if (WARN_ON_ONCE(!cpu_online(cpu_of(rq))))
> +		return;
> +
>   	dl_se->dl_server_active = 1;
>   	enqueue_dl_entity(dl_se, ENQUEUE_WAKEUP);
>   	if (!dl_task(dl_se->rq->curr) || dl_entity_preempt(dl_se, &rq->curr->dl))

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland



^ permalink raw reply	[flat|nested] 7+ messages in thread

* Re: [PATCH] sched/deadline: stop dl_server before CPU goes offline
  2025-10-09 18:47 ` [PATCH] sched/deadline: stop dl_server before CPU goes offline Shrikanth Hegde
  2025-10-09 20:28   ` Marek Szyprowski
@ 2025-10-10  4:59   ` Venkat
  2025-10-14  9:11   ` Juri Lelli
  2025-10-14 11:47   ` [tip: sched/urgent] sched/deadline: Stop " tip-bot2 for Peter Zijlstra (Intel)
  3 siblings, 0 replies; 7+ messages in thread
From: Venkat @ 2025-10-10  4:59 UTC (permalink / raw)
  To: Shrikanth Hegde, linuxppc-dev, LKML, Peter Zijlstra, mingo
  Cc: Peter Zijlstra, juri.lelli, mingo, vincent.guittot, m.szyprowski,
	jstultz



> On 10 Oct 2025, at 12:17 AM, Shrikanth Hegde <sshegde@linux.ibm.com> wrote:
> 
> From: Peter Zijlstra (Intel) <peterz@infradead.org>
> 
> IBM CI tool reported kernel warning[1] when running a CPU removal
> operation through drmgr[2]. i.e "drmgr -c cpu -r -q 1"
> 
> WARNING: CPU: 0 PID: 0 at kernel/sched/cpudeadline.c:219 cpudl_set+0x58/0x170
> NIP [c0000000002b6ed8] cpudl_set+0x58/0x170
> LR [c0000000002b7cb8] dl_server_timer+0x168/0x2a0
> Call Trace:
> [c000000002c2f8c0] init_stack+0x78c0/0x8000 (unreliable)
> [c0000000002b7cb8] dl_server_timer+0x168/0x2a0
> [c00000000034df84] __hrtimer_run_queues+0x1a4/0x390
> [c00000000034f624] hrtimer_interrupt+0x124/0x300
> [c00000000002a230] timer_interrupt+0x140/0x320
> 
> Git bisects to: commit 4ae8d9aa9f9d ("sched/deadline: Fix dl_server getting stuck")
> 
> This happens since: 
> - dl_server hrtimer gets enqueued close to cpu offline, when 
>  kthread_park enqueues a fair task.
> - CPU goes offline and drmgr removes it from cpu_present_mask.
> - hrtimer fires and warning is hit.
> 
> Fix it by stopping the dl_server before CPU is marked dead.
> 
> [1]: https://lore.kernel.org/all/8218e149-7718-4432-9312-f97297c352b9@linux.ibm.com/
> [2]: https://github.com/ibm-power-utilities/powerpc-utils/tree/next/src/drmgr
> 
> [sshegde: wrote the changelog and tested it]
> Fixes: 4ae8d9aa9f9d ("sched/deadline: Fix dl_server getting stuck")
> Reported-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
> Closes: https://lore.kernel.org/all/8218e149-7718-4432-9312-f97297c352b9@linux.ibm.com
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> Signed-off-by: Shrikanth Hegde <sshegde@linux.ibm.com>
> Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
> Tested-by: Shrikanth Hegde <sshegde@linux.ibm.com>

This patch fixes reported issue. Please add below tag.

Tested-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>

Regards,
Venkat.
> ---
> kernel/sched/core.c     | 2 ++
> kernel/sched/deadline.c | 3 +++
> 2 files changed, 5 insertions(+)
> 
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 198d2dd45f59..f1ebf67b48e2 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -8571,10 +8571,12 @@ int sched_cpu_dying(unsigned int cpu)
> sched_tick_stop(cpu);
> 
> rq_lock_irqsave(rq, &rf);
> + update_rq_clock(rq);
> if (rq->nr_running != 1 || rq_has_pinned_tasks(rq)) {
> WARN(true, "Dying CPU not properly vacated!");
> dump_rq_tasks(rq, KERN_WARNING);
> }
> + dl_server_stop(&rq->fair_server);
> rq_unlock_irqrestore(rq, &rf);
> 
> calc_load_migrate(rq);
> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> index 615411a0a881..7b7671060bf9 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -1582,6 +1582,9 @@ void dl_server_start(struct sched_dl_entity *dl_se)
> if (!dl_server(dl_se) || dl_se->dl_server_active)
> return;
> 
> + if (WARN_ON_ONCE(!cpu_online(cpu_of(rq))))
> + return;
> +
> dl_se->dl_server_active = 1;
> enqueue_dl_entity(dl_se, ENQUEUE_WAKEUP);
> if (!dl_task(dl_se->rq->curr) || dl_entity_preempt(dl_se, &rq->curr->dl))
> -- 
> 2.47.3
> 



^ permalink raw reply	[flat|nested] 7+ messages in thread

* Re: [PATCH] sched/deadline: stop dl_server before CPU goes offline
  2025-10-09 18:47 ` [PATCH] sched/deadline: stop dl_server before CPU goes offline Shrikanth Hegde
  2025-10-09 20:28   ` Marek Szyprowski
  2025-10-10  4:59   ` Venkat
@ 2025-10-14  9:11   ` Juri Lelli
  2025-10-17  6:01     ` Youngmin Nam
  2025-10-14 11:47   ` [tip: sched/urgent] sched/deadline: Stop " tip-bot2 for Peter Zijlstra (Intel)
  3 siblings, 1 reply; 7+ messages in thread
From: Juri Lelli @ 2025-10-14  9:11 UTC (permalink / raw)
  To: Shrikanth Hegde
  Cc: peterz, mingo, vincent.guittot, linux-kernel, linuxppc-dev,
	m.szyprowski, venkat88, jstultz

Hello,

On 10/10/25 00:17, Shrikanth Hegde wrote:
> From: Peter Zijlstra (Intel) <peterz@infradead.org>
> 
> IBM CI tool reported kernel warning[1] when running a CPU removal
> operation through drmgr[2]. i.e "drmgr -c cpu -r -q 1"
> 
> WARNING: CPU: 0 PID: 0 at kernel/sched/cpudeadline.c:219 cpudl_set+0x58/0x170
> NIP [c0000000002b6ed8] cpudl_set+0x58/0x170
> LR [c0000000002b7cb8] dl_server_timer+0x168/0x2a0
> Call Trace:
> [c000000002c2f8c0] init_stack+0x78c0/0x8000 (unreliable)
> [c0000000002b7cb8] dl_server_timer+0x168/0x2a0
> [c00000000034df84] __hrtimer_run_queues+0x1a4/0x390
> [c00000000034f624] hrtimer_interrupt+0x124/0x300
> [c00000000002a230] timer_interrupt+0x140/0x320
> 
> Git bisects to: commit 4ae8d9aa9f9d ("sched/deadline: Fix dl_server getting stuck")
> 
> This happens since: 
> - dl_server hrtimer gets enqueued close to cpu offline, when 
>   kthread_park enqueues a fair task.
> - CPU goes offline and drmgr removes it from cpu_present_mask.
> - hrtimer fires and warning is hit.
> 
> Fix it by stopping the dl_server before CPU is marked dead.
> 
> [1]: https://lore.kernel.org/all/8218e149-7718-4432-9312-f97297c352b9@linux.ibm.com/
> [2]: https://github.com/ibm-power-utilities/powerpc-utils/tree/next/src/drmgr
> 
> [sshegde: wrote the changelog and tested it]
> Fixes: 4ae8d9aa9f9d ("sched/deadline: Fix dl_server getting stuck")
> Reported-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
> Closes: https://lore.kernel.org/all/8218e149-7718-4432-9312-f97297c352b9@linux.ibm.com
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> Signed-off-by: Shrikanth Hegde <sshegde@linux.ibm.com>
> Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
> Tested-by: Shrikanth Hegde <sshegde@linux.ibm.com>

Looks good to me.

Acked-by: Juri Lelli <juri.lelli@redhat.com>

Thanks!
Juri



^ permalink raw reply	[flat|nested] 7+ messages in thread

* Re: [PATCH] sched/deadline: stop dl_server before CPU goes offline
  2025-10-14  9:11   ` Juri Lelli
@ 2025-10-17  6:01     ` Youngmin Nam
  2025-10-20  6:08       ` Juri Lelli
  0 siblings, 1 reply; 7+ messages in thread
From: Youngmin Nam @ 2025-10-17  6:01 UTC (permalink / raw)
  To: Juri Lelli
  Cc: Shrikanth Hegde, peterz, mingo, vincent.guittot, linux-kernel,
	linuxppc-dev, m.szyprowski, venkat88, jstultz, d7271.choe,
	soohyuni.kim, bongkyu7.kim, youngmin.nam, jkkkkk.choi

[-- Attachment #1: Type: text/plain, Size: 2156 bytes --]

On Tue, Oct 14, 2025 at 11:11:31AM +0200, Juri Lelli wrote:
> Hello,
> 
> On 10/10/25 00:17, Shrikanth Hegde wrote:
> > From: Peter Zijlstra (Intel) <peterz@infradead.org>
> > 
> > IBM CI tool reported kernel warning[1] when running a CPU removal
> > operation through drmgr[2]. i.e "drmgr -c cpu -r -q 1"
> > 
> > WARNING: CPU: 0 PID: 0 at kernel/sched/cpudeadline.c:219 cpudl_set+0x58/0x170
> > NIP [c0000000002b6ed8] cpudl_set+0x58/0x170
> > LR [c0000000002b7cb8] dl_server_timer+0x168/0x2a0
> > Call Trace:
> > [c000000002c2f8c0] init_stack+0x78c0/0x8000 (unreliable)
> > [c0000000002b7cb8] dl_server_timer+0x168/0x2a0
> > [c00000000034df84] __hrtimer_run_queues+0x1a4/0x390
> > [c00000000034f624] hrtimer_interrupt+0x124/0x300
> > [c00000000002a230] timer_interrupt+0x140/0x320
> > 
> > Git bisects to: commit 4ae8d9aa9f9d ("sched/deadline: Fix dl_server getting stuck")
> > 
> > This happens since: 
> > - dl_server hrtimer gets enqueued close to cpu offline, when 
> >   kthread_park enqueues a fair task.
> > - CPU goes offline and drmgr removes it from cpu_present_mask.
> > - hrtimer fires and warning is hit.
> > 
> > Fix it by stopping the dl_server before CPU is marked dead.
> > 
> > [1]: https://lore.kernel.org/all/8218e149-7718-4432-9312-f97297c352b9@linux.ibm.com/
> > [2]: https://github.com/ibm-power-utilities/powerpc-utils/tree/next/src/drmgr
> > 
> > [sshegde: wrote the changelog and tested it]
> > Fixes: 4ae8d9aa9f9d ("sched/deadline: Fix dl_server getting stuck")
> > Reported-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
> > Closes: https://lore.kernel.org/all/8218e149-7718-4432-9312-f97297c352b9@linux.ibm.com
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> > Signed-off-by: Shrikanth Hegde <sshegde@linux.ibm.com>
> > Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
> > Tested-by: Shrikanth Hegde <sshegde@linux.ibm.com>
> 
> Looks good to me.
> 
> Acked-by: Juri Lelli <juri.lelli@redhat.com>
> 
> Thanks!
> Juri
> 

Hi All,

Could we expect this patch to address the following issue as well?

https://lore.kernel.org/all/aMKTHKfegBk4DgjA@jlelli-thinkpadt14gen4.remote.csb/

Thanks,
Youngmin.

[-- Attachment #2: Type: text/plain, Size: 0 bytes --]



^ permalink raw reply	[flat|nested] 7+ messages in thread

* Re: [PATCH] sched/deadline: stop dl_server before CPU goes offline
  2025-10-17  6:01     ` Youngmin Nam
@ 2025-10-20  6:08       ` Juri Lelli
  0 siblings, 0 replies; 7+ messages in thread
From: Juri Lelli @ 2025-10-20  6:08 UTC (permalink / raw)
  To: Youngmin Nam
  Cc: Shrikanth Hegde, peterz, mingo, vincent.guittot, linux-kernel,
	linuxppc-dev, m.szyprowski, venkat88, jstultz, d7271.choe,
	soohyuni.kim, bongkyu7.kim, jkkkkk.choi

On 17/10/25 15:01, Youngmin Nam wrote:
> On Tue, Oct 14, 2025 at 11:11:31AM +0200, Juri Lelli wrote:
> > Hello,
> > 
> > On 10/10/25 00:17, Shrikanth Hegde wrote:
> > > From: Peter Zijlstra (Intel) <peterz@infradead.org>
> > > 
> > > IBM CI tool reported kernel warning[1] when running a CPU removal
> > > operation through drmgr[2]. i.e "drmgr -c cpu -r -q 1"
> > > 
> > > WARNING: CPU: 0 PID: 0 at kernel/sched/cpudeadline.c:219 cpudl_set+0x58/0x170
> > > NIP [c0000000002b6ed8] cpudl_set+0x58/0x170
> > > LR [c0000000002b7cb8] dl_server_timer+0x168/0x2a0
> > > Call Trace:
> > > [c000000002c2f8c0] init_stack+0x78c0/0x8000 (unreliable)
> > > [c0000000002b7cb8] dl_server_timer+0x168/0x2a0
> > > [c00000000034df84] __hrtimer_run_queues+0x1a4/0x390
> > > [c00000000034f624] hrtimer_interrupt+0x124/0x300
> > > [c00000000002a230] timer_interrupt+0x140/0x320
> > > 
> > > Git bisects to: commit 4ae8d9aa9f9d ("sched/deadline: Fix dl_server getting stuck")
> > > 
> > > This happens since: 
> > > - dl_server hrtimer gets enqueued close to cpu offline, when 
> > >   kthread_park enqueues a fair task.
> > > - CPU goes offline and drmgr removes it from cpu_present_mask.
> > > - hrtimer fires and warning is hit.
> > > 
> > > Fix it by stopping the dl_server before CPU is marked dead.
> > > 
> > > [1]: https://lore.kernel.org/all/8218e149-7718-4432-9312-f97297c352b9@linux.ibm.com/
> > > [2]: https://github.com/ibm-power-utilities/powerpc-utils/tree/next/src/drmgr
> > > 
> > > [sshegde: wrote the changelog and tested it]
> > > Fixes: 4ae8d9aa9f9d ("sched/deadline: Fix dl_server getting stuck")
> > > Reported-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
> > > Closes: https://lore.kernel.org/all/8218e149-7718-4432-9312-f97297c352b9@linux.ibm.com
> > > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> > > Signed-off-by: Shrikanth Hegde <sshegde@linux.ibm.com>
> > > Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
> > > Tested-by: Shrikanth Hegde <sshegde@linux.ibm.com>
> > 
> > Looks good to me.
> > 
> > Acked-by: Juri Lelli <juri.lelli@redhat.com>
> > 
> > Thanks!
> > Juri
> > 
> 
> Hi All,
> 
> Could we expect this patch to address the following issue as well?
> 
> https://lore.kernel.org/all/aMKTHKfegBk4DgjA@jlelli-thinkpadt14gen4.remote.csb/

I don't think I see a direct connection with it.

Thanks,
Juri



^ permalink raw reply	[flat|nested] 7+ messages in thread

* [tip: sched/urgent] sched/deadline: Stop dl_server before CPU goes offline
  2025-10-09 18:47 ` [PATCH] sched/deadline: stop dl_server before CPU goes offline Shrikanth Hegde
                     ` (2 preceding siblings ...)
  2025-10-14  9:11   ` Juri Lelli
@ 2025-10-14 11:47   ` tip-bot2 for Peter Zijlstra (Intel)
  3 siblings, 0 replies; 7+ messages in thread
From: tip-bot2 for Peter Zijlstra (Intel) @ 2025-10-14 11:47 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Peter Zijlstra (Intel), Venkat Rao Bagalkote, Shrikanth Hegde,
	Marek Szyprowski, x86, linux-kernel

The following commit has been merged into the sched/urgent branch of tip:

Commit-ID:     ee6e44dfe6e50b4a5df853d933a96bdff5309e6e
Gitweb:        https://git.kernel.org/tip/ee6e44dfe6e50b4a5df853d933a96bdff5309e6e
Author:        Peter Zijlstra (Intel) <peterz@infradead.org>
AuthorDate:    Fri, 10 Oct 2025 00:17:27 +05:30
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Tue, 14 Oct 2025 13:43:08 +02:00

sched/deadline: Stop dl_server before CPU goes offline

IBM CI tool reported kernel warning[1] when running a CPU removal
operation through drmgr[2]. i.e "drmgr -c cpu -r -q 1"

WARNING: CPU: 0 PID: 0 at kernel/sched/cpudeadline.c:219 cpudl_set+0x58/0x170
NIP [c0000000002b6ed8] cpudl_set+0x58/0x170
LR [c0000000002b7cb8] dl_server_timer+0x168/0x2a0
Call Trace:
[c000000002c2f8c0] init_stack+0x78c0/0x8000 (unreliable)
[c0000000002b7cb8] dl_server_timer+0x168/0x2a0
[c00000000034df84] __hrtimer_run_queues+0x1a4/0x390
[c00000000034f624] hrtimer_interrupt+0x124/0x300
[c00000000002a230] timer_interrupt+0x140/0x320

Git bisects to: commit 4ae8d9aa9f9d ("sched/deadline: Fix dl_server getting stuck")

This happens since:
- dl_server hrtimer gets enqueued close to cpu offline, when
  kthread_park enqueues a fair task.
- CPU goes offline and drmgr removes it from cpu_present_mask.
- hrtimer fires and warning is hit.

Fix it by stopping the dl_server before CPU is marked dead.

[1]: https://lore.kernel.org/all/8218e149-7718-4432-9312-f97297c352b9@linux.ibm.com/
[2]: https://github.com/ibm-power-utilities/powerpc-utils/tree/next/src/drmgr

[sshegde: wrote the changelog and tested it]
Fixes: 4ae8d9aa9f9d ("sched/deadline: Fix dl_server getting stuck")
Closes: https://lore.kernel.org/all/8218e149-7718-4432-9312-f97297c352b9@linux.ibm.com
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reported-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
Signed-off-by: Shrikanth Hegde <sshegde@linux.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Tested-by: Shrikanth Hegde <sshegde@linux.ibm.com>
---
 kernel/sched/core.c     | 2 ++
 kernel/sched/deadline.c | 3 +++
 2 files changed, 5 insertions(+)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 198d2dd..f1ebf67 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -8571,10 +8571,12 @@ int sched_cpu_dying(unsigned int cpu)
 	sched_tick_stop(cpu);
 
 	rq_lock_irqsave(rq, &rf);
+	update_rq_clock(rq);
 	if (rq->nr_running != 1 || rq_has_pinned_tasks(rq)) {
 		WARN(true, "Dying CPU not properly vacated!");
 		dump_rq_tasks(rq, KERN_WARNING);
 	}
+	dl_server_stop(&rq->fair_server);
 	rq_unlock_irqrestore(rq, &rf);
 
 	calc_load_migrate(rq);
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 615411a..7b76710 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1582,6 +1582,9 @@ void dl_server_start(struct sched_dl_entity *dl_se)
 	if (!dl_server(dl_se) || dl_se->dl_server_active)
 		return;
 
+	if (WARN_ON_ONCE(!cpu_online(cpu_of(rq))))
+		return;
+
 	dl_se->dl_server_active = 1;
 	enqueue_dl_entity(dl_se, ENQUEUE_WAKEUP);
 	if (!dl_task(dl_se->rq->curr) || dl_entity_preempt(dl_se, &rq->curr->dl))

^ permalink raw reply related	[flat|nested] 7+ messages in thread

end of thread, other threads:[~2025-10-20  6:08 UTC | newest]

Thread overview: 7+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
     [not found] <CGME20251009202834eucas1p1bfe2bd8fdb6360bc836fa09dd2208a58@eucas1p1.samsung.com>
2025-10-09 18:47 ` [PATCH] sched/deadline: stop dl_server before CPU goes offline Shrikanth Hegde
2025-10-09 20:28   ` Marek Szyprowski
2025-10-10  4:59   ` Venkat
2025-10-14  9:11   ` Juri Lelli
2025-10-17  6:01     ` Youngmin Nam
2025-10-20  6:08       ` Juri Lelli
2025-10-14 11:47   ` [tip: sched/urgent] sched/deadline: Stop " tip-bot2 for Peter Zijlstra (Intel)

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