linux-kernel - Re: [PATCH 1/6] sched/ext: Fix scx vs sched

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Message-ID: <7e4ebd21-3144-4a1a-a736-d9abef21bd4b@arm.com>
Date: Wed, 30 Oct 2024 17:17:43 +0000
From: Christian Loehle <christian.loehle@....com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: mingo@...nel.org, juri.lelli@...hat.com, vincent.guittot@...aro.org,
 dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
 mgorman@...e.de, vschneid@...hat.com, tj@...nel.org, void@...ifault.com,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/6] sched/ext: Fix scx vs sched_delayed

On 10/30/24 15:54, Peter Zijlstra wrote:
> On Wed, Oct 30, 2024 at 03:50:05PM +0000, Christian Loehle wrote:
>> On 10/30/24 15:12, Peter Zijlstra wrote:
>>> Commit 98442f0ccd82 ("sched: Fix delayed_dequeue vs
>>> switched_from_fair()") forgot about scx :/
>>>
>>> Fixes: 98442f0ccd82 ("sched: Fix delayed_dequeue vs switched_from_fair()")
>>> Reported-by: Tejun Heo <tj@...nel.org>
>>> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
>>> Link: https://lkml.kernel.org/r/20241030104934.GK14555@noisy.programming.kicks-ass.net
>>> ---
>>>  kernel/sched/ext.c |   14 ++++++++++++--
>>>  1 file changed, 12 insertions(+), 2 deletions(-)
>>>
>>> --- a/kernel/sched/ext.c
>>> +++ b/kernel/sched/ext.c
>>> @@ -4489,11 +4489,16 @@ static void scx_ops_disable_workfn(struc
>>>  	scx_task_iter_start(&sti);
>>>  	while ((p = scx_task_iter_next_locked(&sti))) {
>>>  		const struct sched_class *old_class = p->sched_class;
>>> +		const struct sched_class *new_class =
>>> +			__setscheduler_class(p->policy, p->prio);
>>>  		struct sched_enq_and_set_ctx ctx;
>>>  
>>> +		if (old_class != new_class && p->se.sched_delayed)
>>> +			dequeue_task(task_rq(p), p, DEQUEUE_SLEEP | DEQUEUE_DELAYED);
>>> +
>>>  		sched_deq_and_put_task(p, DEQUEUE_SAVE | DEQUEUE_MOVE, &ctx);
>>>  
>>> -		p->sched_class = __setscheduler_class(p->policy, p->prio);
>>> +		p->sched_class = new_class;
>>>  		check_class_changing(task_rq(p), p, old_class);
>>>  
>>>  		sched_enq_and_set_task(&ctx);
>>> @@ -5199,12 +5204,17 @@ static int scx_ops_enable(struct sched_e
>>>  	scx_task_iter_start(&sti);
>>>  	while ((p = scx_task_iter_next_locked(&sti))) {
>>>  		const struct sched_class *old_class = p->sched_class;
>>> +		const struct sched_class *new_class =
>>> +			__setscheduler_class(p->policy, p->prio);
>>>  		struct sched_enq_and_set_ctx ctx;
>>>  
>>> +		if (old_class != new_class && p->se.sched_delayed)
>>> +			dequeue_task(task_rq(p), p, DEQUEUE_SLEEP | DEQUEE_DELAYED);
>>> +
>>
>> s/DEQUEE_DELAYED/DEQUEUE_DELAYED
> 
> Bah, typing so hard..
> 
>> Anyway, no luck for me applying the series onto sched/core scx's for-next or rc5.
>> Any hint or do you mind supplying a branch?
> 
> I think I did it on top of tip/master..

0b9c113ad1c2 (tip/master) Merge branch into tip/master: 'x86/sev'
results in the following diff for me (line number mismatch by 5), stops applying from 2/6:
-- 

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 65334c13ffa5..2b5f1742299a 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -4494,11 +4494,16 @@ static void scx_ops_disable_workfn(struct kthread_work *work)
        scx_task_iter_start(&sti);
        while ((p = scx_task_iter_next_locked(&sti))) {
                const struct sched_class *old_class = p->sched_class;
+               const struct sched_class *new_class =
+                       __setscheduler_class(p->policy, p->prio);
                struct sched_enq_and_set_ctx ctx;
 
+               if (old_class != new_class && p->se.sched_delayed)
+                       dequeue_task(task_rq(p), p, DEQUEUE_SLEEP | DEQUEUE_DELAYED);
+
                sched_deq_and_put_task(p, DEQUEUE_SAVE | DEQUEUE_MOVE, &ctx);
 
-               p->sched_class = __setscheduler_class(p->policy, p->prio);
+               p->sched_class = new_class;
                check_class_changing(task_rq(p), p, old_class);
 
                sched_enq_and_set_task(&ctx);