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    SubjectRe: [PATCH 1/2] sched/deadline: add per rq tracking of admitted bandwidth
    On 11/02/16 09:25, Steven Rostedt wrote:
    > On Thu, 11 Feb 2016 14:05:45 +0100
    > luca abeni <luca.abeni@unitn.it> wrote:
    >
    >
    > > Well, I never used the rq utilization to re-build the root_domain
    > > utilization (and I never played with root domains too much... :)...
    > > So, I do not really know. Maybe the code should do:
    > > raw_spin_lock(&rq->lock);
    > > raw_spin_lock(&cpu_rq(cpu)->lock);
    >
    > Of course you want to use double_rq_lock() here instead.
    >

    Right. Is something like this completely out of question/broken?

    I slighly tested it with Steve's test and I don't see the warning
    anymore (sched_debug looks good as well); but my confidence is still
    pretty low. :(

    --->8---

    From 9713e12bc682ca364e62f9d69bcd44598c50a8a9 Mon Sep 17 00:00:00 2001
    From: Juri Lelli <juri.lelli@arm.com>
    Date: Thu, 11 Feb 2016 16:55:49 +0000
    Subject: [PATCH] fixup! sched/deadline: add per rq tracking of admitted
    bandwidth

    Signed-off-by: Juri Lelli <juri.lelli@arm.com>
    ---
    include/linux/init_task.h | 1 +
    include/linux/sched.h | 1 +
    kernel/sched/core.c | 5 ++++-
    kernel/sched/deadline.c | 26 +++++++++++++++++++++++++-
    4 files changed, 31 insertions(+), 2 deletions(-)

    diff --git a/include/linux/init_task.h b/include/linux/init_task.h
    index f2cb8d4..c582f9d 100644
    --- a/include/linux/init_task.h
    +++ b/include/linux/init_task.h
    @@ -199,6 +199,7 @@ extern struct task_group root_task_group;
    .policy = SCHED_NORMAL, \
    .cpus_allowed = CPU_MASK_ALL, \
    .nr_cpus_allowed= NR_CPUS, \
    + .fallback_cpu = -1, \
    .mm = NULL, \
    .active_mm = &init_mm, \
    .restart_block = { \
    diff --git a/include/linux/sched.h b/include/linux/sched.h
    index a10494a..a6fc95c 100644
    --- a/include/linux/sched.h
    +++ b/include/linux/sched.h
    @@ -1401,6 +1401,7 @@ struct task_struct {
    struct task_struct *last_wakee;

    int wake_cpu;
    + int fallback_cpu;
    #endif
    int on_rq;

    diff --git a/kernel/sched/core.c b/kernel/sched/core.c
    index 7fb9246..4e4bc41 100644
    --- a/kernel/sched/core.c
    +++ b/kernel/sched/core.c
    @@ -1442,7 +1442,8 @@ static int select_fallback_rq(int cpu, struct task_struct *p)
    continue;
    if (!cpu_active(dest_cpu))
    continue;
    - if (cpumask_test_cpu(dest_cpu, tsk_cpus_allowed(p)))
    + if (cpumask_test_cpu(dest_cpu, tsk_cpus_allowed(p))) {
    + p->fallback_cpu = dest_cpu;
    return dest_cpu;
    }
    }
    @@ -1490,6 +1491,7 @@ out:
    }
    }

    + p->fallback_cpu = dest_cpu;
    return dest_cpu;
    }

    @@ -1954,6 +1956,7 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
    if (task_cpu(p) != cpu) {
    wake_flags |= WF_MIGRATED;
    set_task_cpu(p, cpu);
    + p->fallback_cpu = -1;
    }
    #endif /* CONFIG_SMP */

    diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
    index 6368f43..1eccecf 100644
    --- a/kernel/sched/deadline.c
    +++ b/kernel/sched/deadline.c
    @@ -1043,6 +1043,21 @@ static void yield_task_dl(struct rq *rq)

    #ifdef CONFIG_SMP

    +static void swap_task_ac_bw(struct task_struct *p,
    + struct rq *from,
    + struct rq *to)
    +{
    + unsigned long flags;
    +
    + lockdep_assert_held(&p->pi_lock);
    + local_irq_save(flags);
    + double_rq_lock(from, to);
    + __dl_sub_ac(from, p->dl.dl_bw);
    + __dl_add_ac(to, p->dl.dl_bw);
    + double_rq_unlock(from, to);
    + local_irq_restore(flags);
    +}
    +
    static int find_later_rq(struct task_struct *task);

    static int
    @@ -1077,8 +1092,10 @@ select_task_rq_dl(struct task_struct *p, int cpu, int sd_flag, int flags)
    if (target != -1 &&
    (dl_time_before(p->dl.deadline,
    cpu_rq(target)->dl.earliest_dl.curr) ||
    - (cpu_rq(target)->dl.dl_nr_running == 0)))
    + (cpu_rq(target)->dl.dl_nr_running == 0))) {
    cpu = target;
    + swap_task_ac_bw(p, rq, cpu_rq(target));
    + }
    }
    rcu_read_unlock();

    @@ -1807,6 +1824,12 @@ static void prio_changed_dl(struct rq *rq, struct task_struct *p,
    switched_to_dl(rq, p);
    }

    +static void migrate_task_rq_dl(struct task_struct *p)
    +{
    + if (p->fallback_cpu != -1)
    + swap_task_ac_bw(p, task_rq(p), cpu_rq(p->fallback_cpu));
    +}
    +
    const struct sched_class dl_sched_class = {
    .next = &rt_sched_class,
    .enqueue_task = enqueue_task_dl,
    @@ -1820,6 +1843,7 @@ const struct sched_class dl_sched_class = {

    #ifdef CONFIG_SMP
    .select_task_rq = select_task_rq_dl,
    + .migrate_task_rq = migrate_task_rq_dl,
    .set_cpus_allowed = set_cpus_allowed_dl,
    .rq_online = rq_online_dl,
    .rq_offline = rq_offline_dl,
    --
    2.7.0
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