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Subject[PATCH v6 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>

---

v5->v6: minor changes required to rebase on top of Waiman Long's cpuset
for cgroup v2 set.
---
kernel/cgroup/cpuset.c | 70 +++++++++++++++++++++---------------------
1 file changed, 35 insertions(+), 35 deletions(-)

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index f0decd8165e7..54b8ff5de7c8 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -345,7 +345,7 @@ 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;

@@ -1220,7 +1220,7 @@ static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd,
* Newly added CPUs will be removed from effective_cpus and
* newly deleted ones will be added back to effective_cpus.
*/
- spin_lock_irq(&callback_lock);
+ raw_spin_lock_irq(&callback_lock);
if (adding) {
cpumask_or(parent->subparts_cpus,
parent->subparts_cpus, tmp->addmask);
@@ -1239,7 +1239,7 @@ static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd,
}

parent->nr_subparts_cpus = cpumask_weight(parent->subparts_cpus);
- spin_unlock_irq(&callback_lock);
+ raw_spin_unlock_irq(&callback_lock);

return cmd == partcmd_update;
}
@@ -1344,7 +1344,7 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp)
continue;
rcu_read_unlock();

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

cpumask_copy(cp->effective_cpus, tmp->new_cpus);
if (cp->nr_subparts_cpus &&
@@ -1375,7 +1375,7 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp)
= cpumask_weight(cp->subparts_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));
@@ -1493,7 +1493,7 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
return -EINVAL;
}

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

/*
@@ -1504,7 +1504,7 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
cs->cpus_allowed);
cs->nr_subparts_cpus = cpumask_weight(cs->subparts_cpus);
}
- spin_unlock_irq(&callback_lock);
+ raw_spin_unlock_irq(&callback_lock);

update_cpumasks_hier(cs, &tmp);

@@ -1698,9 +1698,9 @@ 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));
@@ -1768,9 +1768,9 @@ 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);
@@ -1861,9 +1861,9 @@ 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();
@@ -2366,7 +2366,7 @@ 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:
@@ -2388,7 +2388,7 @@ 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;
}

@@ -2698,14 +2698,14 @@ 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;
cs->use_parent_ecpus = true;
parent->child_ecpus_count++;
}
- spin_unlock_irq(&callback_lock);
+ raw_spin_unlock_irq(&callback_lock);

if (!test_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags))
goto out_unlock;
@@ -2732,12 +2732,12 @@ 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;
@@ -2790,7 +2790,7 @@ 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);
@@ -2801,7 +2801,7 @@ 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);
}

@@ -2902,12 +2902,12 @@ 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,
@@ -2944,10 +2944,10 @@ 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);
@@ -3102,7 +3102,7 @@ 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);
/*
@@ -3122,17 +3122,17 @@ static void cpuset_hotplug_workfn(struct work_struct *work)
}
}
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);
}

@@ -3233,11 +3233,11 @@ 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)
@@ -3285,11 +3285,11 @@ 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;
}
@@ -3381,14 +3381,14 @@ 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;
}

--
2.17.2
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