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Date: Wed, 7 Nov 2018 10:59:34 +0100
From: Juri Lelli <juri.lelli@...hat.com>
To: lizefan@...wei.com, tj@...nel.org
Cc: linux-kernel@...r.kernel.org, luca.abeni@...tannapisa.it,
claudio@...dence.eu.com, tommaso.cucinotta@...tannapisa.it,
bristot@...hat.com, mathieu.poirier@...aro.org,
cgroups@...r.kernel.org, peterz@...radead.org, mingo@...hat.com,
rostedt@...dmis.org
Subject: Re: [PATCH v5 3/5] cgroup/cpuset: make callback_lock raw
Hi,
Ping.
Thanks,
- Juri
On 25/09/18 16:34, Juri Lelli wrote:
> Hi Li Zefan and Tejun Heo,
>
> It would be great if you could please have a look at the proposed change
> below (and the rest of the set of course :-).
>
> Another bit that I'd be more comfortable after hearing your word on it
> is this one (discussed over 5/5):
>
> https://lore.kernel.org/lkml/20180925130750.GA25664@localhost.localdomain/
>
> Best,
>
> - Juri
>
> On 03/09/18 16:27, Juri Lelli wrote:
> > 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@...hat.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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