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    Subject[PATCH v5 3/5] cgroup/cpuset: make callback_lock raw
    Date
    callback_lock grants the holder read-only access to cpusets.  For fixing
    a synchronization issue between cpusets and scheduler core, it is now
    required to make callback_lock available to core scheduler code.

    Convert callback_lock to raw_spin_lock, so that it will be always safe
    to acquire it from atomic context.

    Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
    ---
    kernel/cgroup/cpuset.c | 66 +++++++++++++++++++++---------------------
    1 file changed, 33 insertions(+), 33 deletions(-)

    diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
    index 266f10cb7222..5b43f482fa0f 100644
    --- a/kernel/cgroup/cpuset.c
    +++ b/kernel/cgroup/cpuset.c
    @@ -288,7 +288,7 @@ static struct cpuset top_cpuset = {
    */

    static DEFINE_MUTEX(cpuset_mutex);
    -static DEFINE_SPINLOCK(callback_lock);
    +static DEFINE_RAW_SPINLOCK(callback_lock);

    static struct workqueue_struct *cpuset_migrate_mm_wq;

    @@ -922,9 +922,9 @@ static void update_cpumasks_hier(struct cpuset *cs, struct cpumask *new_cpus)
    continue;
    rcu_read_unlock();

    - spin_lock_irq(&callback_lock);
    + raw_spin_lock_irq(&callback_lock);
    cpumask_copy(cp->effective_cpus, new_cpus);
    - spin_unlock_irq(&callback_lock);
    + raw_spin_unlock_irq(&callback_lock);

    WARN_ON(!is_in_v2_mode() &&
    !cpumask_equal(cp->cpus_allowed, cp->effective_cpus));
    @@ -989,9 +989,9 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
    if (retval < 0)
    return retval;

    - spin_lock_irq(&callback_lock);
    + raw_spin_lock_irq(&callback_lock);
    cpumask_copy(cs->cpus_allowed, trialcs->cpus_allowed);
    - spin_unlock_irq(&callback_lock);
    + raw_spin_unlock_irq(&callback_lock);

    /* use trialcs->cpus_allowed as a temp variable */
    update_cpumasks_hier(cs, trialcs->cpus_allowed);
    @@ -1175,9 +1175,9 @@ static void update_nodemasks_hier(struct cpuset *cs, nodemask_t *new_mems)
    continue;
    rcu_read_unlock();

    - spin_lock_irq(&callback_lock);
    + raw_spin_lock_irq(&callback_lock);
    cp->effective_mems = *new_mems;
    - spin_unlock_irq(&callback_lock);
    + raw_spin_unlock_irq(&callback_lock);

    WARN_ON(!is_in_v2_mode() &&
    !nodes_equal(cp->mems_allowed, cp->effective_mems));
    @@ -1245,9 +1245,9 @@ static int update_nodemask(struct cpuset *cs, struct cpuset *trialcs,
    if (retval < 0)
    goto done;

    - spin_lock_irq(&callback_lock);
    + raw_spin_lock_irq(&callback_lock);
    cs->mems_allowed = trialcs->mems_allowed;
    - spin_unlock_irq(&callback_lock);
    + raw_spin_unlock_irq(&callback_lock);

    /* use trialcs->mems_allowed as a temp variable */
    update_nodemasks_hier(cs, &trialcs->mems_allowed);
    @@ -1338,9 +1338,9 @@ static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs,
    spread_flag_changed = ((is_spread_slab(cs) != is_spread_slab(trialcs))
    || (is_spread_page(cs) != is_spread_page(trialcs)));

    - spin_lock_irq(&callback_lock);
    + raw_spin_lock_irq(&callback_lock);
    cs->flags = trialcs->flags;
    - spin_unlock_irq(&callback_lock);
    + raw_spin_unlock_irq(&callback_lock);

    if (!cpumask_empty(trialcs->cpus_allowed) && balance_flag_changed)
    rebuild_sched_domains_locked();
    @@ -1755,7 +1755,7 @@ static int cpuset_common_seq_show(struct seq_file *sf, void *v)
    cpuset_filetype_t type = seq_cft(sf)->private;
    int ret = 0;

    - spin_lock_irq(&callback_lock);
    + raw_spin_lock_irq(&callback_lock);

    switch (type) {
    case FILE_CPULIST:
    @@ -1774,7 +1774,7 @@ static int cpuset_common_seq_show(struct seq_file *sf, void *v)
    ret = -EINVAL;
    }

    - spin_unlock_irq(&callback_lock);
    + raw_spin_unlock_irq(&callback_lock);
    return ret;
    }

    @@ -1989,12 +1989,12 @@ static int cpuset_css_online(struct cgroup_subsys_state *css)

    cpuset_inc();

    - spin_lock_irq(&callback_lock);
    + raw_spin_lock_irq(&callback_lock);
    if (is_in_v2_mode()) {
    cpumask_copy(cs->effective_cpus, parent->effective_cpus);
    cs->effective_mems = parent->effective_mems;
    }
    - spin_unlock_irq(&callback_lock);
    + raw_spin_unlock_irq(&callback_lock);

    if (!test_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags))
    goto out_unlock;
    @@ -2021,12 +2021,12 @@ static int cpuset_css_online(struct cgroup_subsys_state *css)
    }
    rcu_read_unlock();

    - spin_lock_irq(&callback_lock);
    + raw_spin_lock_irq(&callback_lock);
    cs->mems_allowed = parent->mems_allowed;
    cs->effective_mems = parent->mems_allowed;
    cpumask_copy(cs->cpus_allowed, parent->cpus_allowed);
    cpumask_copy(cs->effective_cpus, parent->cpus_allowed);
    - spin_unlock_irq(&callback_lock);
    + raw_spin_unlock_irq(&callback_lock);
    out_unlock:
    mutex_unlock(&cpuset_mutex);
    return 0;
    @@ -2065,7 +2065,7 @@ static void cpuset_css_free(struct cgroup_subsys_state *css)
    static void cpuset_bind(struct cgroup_subsys_state *root_css)
    {
    mutex_lock(&cpuset_mutex);
    - spin_lock_irq(&callback_lock);
    + raw_spin_lock_irq(&callback_lock);

    if (is_in_v2_mode()) {
    cpumask_copy(top_cpuset.cpus_allowed, cpu_possible_mask);
    @@ -2076,7 +2076,7 @@ static void cpuset_bind(struct cgroup_subsys_state *root_css)
    top_cpuset.mems_allowed = top_cpuset.effective_mems;
    }

    - spin_unlock_irq(&callback_lock);
    + raw_spin_unlock_irq(&callback_lock);
    mutex_unlock(&cpuset_mutex);
    }

    @@ -2174,12 +2174,12 @@ hotplug_update_tasks_legacy(struct cpuset *cs,
    {
    bool is_empty;

    - spin_lock_irq(&callback_lock);
    + raw_spin_lock_irq(&callback_lock);
    cpumask_copy(cs->cpus_allowed, new_cpus);
    cpumask_copy(cs->effective_cpus, new_cpus);
    cs->mems_allowed = *new_mems;
    cs->effective_mems = *new_mems;
    - spin_unlock_irq(&callback_lock);
    + raw_spin_unlock_irq(&callback_lock);

    /*
    * Don't call update_tasks_cpumask() if the cpuset becomes empty,
    @@ -2216,10 +2216,10 @@ hotplug_update_tasks(struct cpuset *cs,
    if (nodes_empty(*new_mems))
    *new_mems = parent_cs(cs)->effective_mems;

    - spin_lock_irq(&callback_lock);
    + raw_spin_lock_irq(&callback_lock);
    cpumask_copy(cs->effective_cpus, new_cpus);
    cs->effective_mems = *new_mems;
    - spin_unlock_irq(&callback_lock);
    + raw_spin_unlock_irq(&callback_lock);

    if (cpus_updated)
    update_tasks_cpumask(cs);
    @@ -2312,21 +2312,21 @@ static void cpuset_hotplug_workfn(struct work_struct *work)

    /* synchronize cpus_allowed to cpu_active_mask */
    if (cpus_updated) {
    - spin_lock_irq(&callback_lock);
    + raw_spin_lock_irq(&callback_lock);
    if (!on_dfl)
    cpumask_copy(top_cpuset.cpus_allowed, &new_cpus);
    cpumask_copy(top_cpuset.effective_cpus, &new_cpus);
    - spin_unlock_irq(&callback_lock);
    + raw_spin_unlock_irq(&callback_lock);
    /* we don't mess with cpumasks of tasks in top_cpuset */
    }

    /* synchronize mems_allowed to N_MEMORY */
    if (mems_updated) {
    - spin_lock_irq(&callback_lock);
    + raw_spin_lock_irq(&callback_lock);
    if (!on_dfl)
    top_cpuset.mems_allowed = new_mems;
    top_cpuset.effective_mems = new_mems;
    - spin_unlock_irq(&callback_lock);
    + raw_spin_unlock_irq(&callback_lock);
    update_tasks_nodemask(&top_cpuset);
    }

    @@ -2425,11 +2425,11 @@ void cpuset_cpus_allowed(struct task_struct *tsk, struct cpumask *pmask)
    {
    unsigned long flags;

    - spin_lock_irqsave(&callback_lock, flags);
    + raw_spin_lock_irqsave(&callback_lock, flags);
    rcu_read_lock();
    guarantee_online_cpus(task_cs(tsk), pmask);
    rcu_read_unlock();
    - spin_unlock_irqrestore(&callback_lock, flags);
    + raw_spin_unlock_irqrestore(&callback_lock, flags);
    }

    void cpuset_cpus_allowed_fallback(struct task_struct *tsk)
    @@ -2477,11 +2477,11 @@ nodemask_t cpuset_mems_allowed(struct task_struct *tsk)
    nodemask_t mask;
    unsigned long flags;

    - spin_lock_irqsave(&callback_lock, flags);
    + raw_spin_lock_irqsave(&callback_lock, flags);
    rcu_read_lock();
    guarantee_online_mems(task_cs(tsk), &mask);
    rcu_read_unlock();
    - spin_unlock_irqrestore(&callback_lock, flags);
    + raw_spin_unlock_irqrestore(&callback_lock, flags);

    return mask;
    }
    @@ -2573,14 +2573,14 @@ bool __cpuset_node_allowed(int node, gfp_t gfp_mask)
    return true;

    /* Not hardwall and node outside mems_allowed: scan up cpusets */
    - spin_lock_irqsave(&callback_lock, flags);
    + raw_spin_lock_irqsave(&callback_lock, flags);

    rcu_read_lock();
    cs = nearest_hardwall_ancestor(task_cs(current));
    allowed = node_isset(node, cs->mems_allowed);
    rcu_read_unlock();

    - spin_unlock_irqrestore(&callback_lock, flags);
    + raw_spin_unlock_irqrestore(&callback_lock, flags);
    return allowed;
    }

    --
    2.17.1
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