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From: Juri Lelli <juri.lelli@redhat.com>
To: Dietmar Eggemann <dietmar.eggemann@arm.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 08:52:25 +0200
Message-ID: <20190808065225.GD29310@localhost.localdomain> (raw)
In-Reply-To: <34710762-f813-3913-0e55-fde7c91c6c2d@arm.com>

Hi Dietmar,

On 07/08/19 18:31, 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.
> 
> ...
> [    0.530216] root domain span: 0-5 (max cpu_capacity = 1024)
> [    0.538655] devtmpfs: initialized
> [    0.556485] update_curr: rq mismatch rq[0] != rq[4]
> [    0.561519] update_curr: rq mismatch rq[0] != rq[4]
> [    0.566497] update_curr: rq mismatch rq[0] != rq[4]
> [    0.571443] update_curr: rq mismatch rq[0] != rq[4]
> [    0.576762] update_curr: rq mismatch rq[2] != rq[4]
> [    0.581674] update_curr: rq mismatch rq[2] != rq[4]
> [    0.586569] ------------[ cut here ]------------
> [    0.591220] WARNING: CPU: 2 PID: 2 at kernel/sched/deadline.c:916 start_dl_timer+0x160/0x178
> [    0.599686] Modules linked in:
> [    0.602756] CPU: 2 PID: 2 Comm: kthreadd Tainted: G        W         5.3.0-rc3-00013-ga33cf033cc99-dirty #64
> [    0.612620] Hardware name: ARM Juno development board (r0) (DT)
> [    0.618560] pstate: 60000085 (nZCv daIf -PAN -UAO)
> [    0.623369] pc : start_dl_timer+0x160/0x178
> [    0.627572] lr : start_dl_timer+0x160/0x178
> [    0.631768] sp : ffff000010013cb0
> ...
> [    0.715075] Call trace:
> [    0.717531]  start_dl_timer+0x160/0x178
> [    0.721382]  update_curr_dl_se+0x108/0x208
> [    0.725494]  dl_server_update+0x2c/0x38
> [    0.729348]  update_curr+0x1b4/0x3b8
> [    0.732934]  task_tick_fair+0x74/0xa88
> [    0.736698]  scheduler_tick+0x94/0x110
> [    0.740461]  update_process_times+0x48/0x60
> ...
> 
> Seems to be related to the fact that the rq can change:
> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index e4c14851a34c..5e3130a200ec 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -891,8 +891,17 @@ static void update_curr(struct cfs_rq *cfs_rq)
>                 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)
> +               if (curtask->server) {
> +                       struct rq *rq = rq_of(cfs_rq);
> +                       struct rq *rq2 = curtask->server->rq;
> +
> +                       if (rq != rq2) {
> +                               printk("update_curr: rq mismatch rq[%d] != rq[%d]\n",
> +                                      cpu_of(rq), cpu_of(rq2));
> +                       }
> +
>                         dl_server_update(curtask->server, delta_exec);
> +               }
>         }
> 
> ...

Yeah, I actually noticed the same. Some debugging seems to point to
early boot spawning of kthreads. I can reliably for example attribute
this mismatch to ksoftirqd(s). It looks like they can avoid the
dl_server assignment in pick_next_task_dl() and this breaks things.
Still need to figure out why this happens and how to fix it, though.

Best,

Juri

  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 [this message]
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
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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