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From: Dietmar Eggemann <dietmar.eggemann@arm.com>
To: Juri Lelli <juri.lelli@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	mingo@kernel.org, linux-kernel@vger.kernel.org,
	luca.abeni@santannapisa.it, bristot@redhat.com,
	balsini@android.com, dvyukov@google.com, tglx@linutronix.de,
	vpillai@digitalocean.com, rostedt@goodmis.org
Subject: Re: [RFC][PATCH 12/13] sched/deadline: Introduce deadline servers
Date: Thu, 8 Aug 2019 10:57:13 +0200
Message-ID: <99a8339d-8e06-bff8-284b-1829d0683a7a@arm.com> (raw)
In-Reply-To: <20190808084652.GG29310@localhost.localdomain>

On 8/8/19 10:46 AM, Juri Lelli wrote:
> On 08/08/19 10:11, Dietmar Eggemann wrote:
>> On 8/8/19 9:56 AM, Peter Zijlstra wrote:
>>> On Wed, Aug 07, 2019 at 06:31:59PM +0200, Dietmar Eggemann wrote:
>>>> On 7/26/19 4:54 PM, Peter Zijlstra wrote:
>>>>>
>>>>>
>>>>> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
>>>>
>>>> [...]
>>>>
>>>>> @@ -889,6 +891,8 @@ static void update_curr(struct cfs_rq *c
>>>>>  		trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
>>>>>  		cgroup_account_cputime(curtask, delta_exec);
>>>>>  		account_group_exec_runtime(curtask, delta_exec);
>>>>> +		if (curtask->server)
>>>>> +			dl_server_update(curtask->server, delta_exec);
>>>>>  	}
>>>>
>>>> I get a lockdep_assert_held(&rq->lock) related warning in start_dl_timer()
>>>> when running the full stack.
>>>
>>> That would seem to imply a stale curtask->server value; the hunk below:
>>>
>>> --- a/kernel/sched/core.c
>>> +++ b/kernel/sched/core.c
>>> @@ -3756,8 +3756,11 @@ pick_next_task(struct rq *rq, struct tas
>>>
>>>         for_each_class(class) {
>>>                 p = class->pick_next_task(rq, NULL, NULL);
>>> -               if (p)
>>> +               if (p) {
>>> +                       if (p->sched_class == class && p->server)
>>> +                               p->server = NULL;
>>>                         return p;
>>> +               }
>>>         }
>>>
>>>
>>> Was supposed to clear p->server, but clearly something is going 'funny'.
>>
>> What about the fast path in pick_next_task()?
>>
>> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
>> index bffe849b5a42..f1ea6ae16052 100644
>> --- a/kernel/sched/core.c
>> +++ b/kernel/sched/core.c
>> @@ -3742,6 +3742,9 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
>>                 if (unlikely(!p))
>>                         p = idle_sched_class.pick_next_task(rq, prev, rf);
>>  
>> +               if (p->sched_class == &fair_sched_class && p->server)
>> +                       p->server = NULL;
>> +
> 
> Hummm, but then who sets it back to the correct server. AFAIU
> update_curr() needs a ->server to do the correct DL accounting?

Ah, OK, this would kill the whole functionality ;-)


  reply index

Thread overview: 63+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-26 14:54 [RFC][PATCH 00/13] SCHED_DEADLINE server infrastructure Peter Zijlstra
2019-07-26 14:54 ` [RFC][PATCH 01/13] sched/deadline: Impose global limits on sched_attr::sched_period Peter Zijlstra
2019-07-29  8:57   ` Juri Lelli
2019-07-29 11:45     ` Daniel Bristot de Oliveira
2019-08-02 17:21   ` Alessio Balsini
2019-08-05 11:53     ` Peter Zijlstra
2019-08-22 12:29       ` Alessio Balsini
2019-08-22 16:51         ` Peter Zijlstra
2019-08-31 14:41           ` Alessio Balsini
2019-09-02  9:16             ` Peter Zijlstra
2019-09-02 12:31               ` Peter Zijlstra
2019-09-04 10:16               ` Steven Rostedt
2019-09-04 11:30                 ` Peter Zijlstra
2019-09-04 13:24                   ` Joel Fernandes
2019-09-04 14:11                     ` Will Deacon
2019-09-04 14:35                       ` Joel Fernandes
2019-09-04 15:52                     ` Peter Zijlstra
2019-10-23 17:17       ` [PATCH 4.4 4.9 4.14] loop: Add LOOP_SET_DIRECT_IO to compat ioctl Alessio Balsini
2019-10-23 17:22         ` Alessio Balsini
2019-10-25  0:17         ` Sasha Levin
2020-05-20 18:38   ` [RFC][PATCH 01/13] sched/deadline: Impose global limits on sched_attr::sched_period Juri Lelli
2020-05-21 13:45     ` Daniel Bristot de Oliveira
2020-06-16 12:21   ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2019-07-26 14:54 ` [RFC][PATCH 02/13] stop_machine: Fix stop_cpus_in_progress ordering Peter Zijlstra
2019-07-30 13:16   ` Phil Auld
2019-07-30 13:22   ` Steven Rostedt
2019-07-26 14:54 ` [RFC][PATCH 03/13] sched: Fix kerneldoc comment for ia64_set_curr_task Peter Zijlstra
2019-07-26 14:54 ` [RFC][PATCH 04/13] sched/{rt,deadline}: Fix set_next_task vs pick_next_task Peter Zijlstra
2019-07-29  9:25   ` Juri Lelli
2019-07-29 11:15     ` Peter Zijlstra
2019-07-29 11:27       ` Juri Lelli
2019-07-29 13:04         ` Peter Zijlstra
2019-07-29 13:17           ` Juri Lelli
2019-07-29 14:40             ` Peter Zijlstra
2019-07-26 14:54 ` [RFC][PATCH 05/13] sched: Add task_struct pointer to sched_class::set_curr_task Peter Zijlstra
2019-07-26 14:54 ` [RFC][PATCH 06/13] sched/fair: Export newidle_balance() Peter Zijlstra
2019-07-26 14:54 ` [RFC][PATCH 07/13] sched: Allow put_prev_task() to drop rq->lock Peter Zijlstra
2019-07-26 14:54 ` [RFC][PATCH 08/13] sched: Rework pick_next_task() slow-path Peter Zijlstra
2019-07-26 14:54 ` [RFC][PATCH 09/13] sched: Unify runtime accounting across classes Peter Zijlstra
2019-07-26 14:54 ` [RFC][PATCH 10/13] sched/deadline: Collect sched_dl_entity initialization Peter Zijlstra
2019-07-26 14:54 ` [RFC][PATCH 11/13] sched/deadline: Move bandwidth accounting into {en,de}queue_dl_entity Peter Zijlstra
2019-07-26 14:54 ` [RFC][PATCH 12/13] sched/deadline: Introduce deadline servers Peter Zijlstra
2019-08-07 16:31   ` Dietmar Eggemann
2019-08-08  6:52     ` Juri Lelli
2019-08-08  7:52       ` Dietmar Eggemann
2019-08-08  7:56     ` Peter Zijlstra
2019-08-08  8:11       ` Dietmar Eggemann
2019-08-08  8:46         ` Juri Lelli
2019-08-08  8:57           ` Dietmar Eggemann [this message]
2019-08-08  9:27             ` Juri Lelli
2019-08-08  9:45               ` Juri Lelli
2019-08-30 11:24                 ` Peter Zijlstra
2019-09-06  9:36                   ` Juri Lelli
2019-08-08 10:31           ` Peter Zijlstra
2019-08-09  7:13             ` Juri Lelli
2019-08-08  6:59   ` Juri Lelli
2019-08-09  9:17   ` Dietmar Eggemann
2019-08-09 12:16     ` Juri Lelli
2019-07-26 14:54 ` [RFC][PATCH 13/13] sched/fair: Add trivial fair server Peter Zijlstra
2019-07-26 20:01 ` [RFC][PATCH 00/13] SCHED_DEADLINE server infrastructure luca abeni
2019-09-03 14:27 ` Alessio Balsini
2019-09-04 10:50   ` Juri Lelli
2019-09-04 11:32     ` Peter Zijlstra

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