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From: Juri Lelli <juri.lelli@redhat.com>
To: lizefan@huawei.com, tj@kernel.org
Cc: linux-kernel@vger.kernel.org, luca.abeni@santannapisa.it,
	claudio@evidence.eu.com, tommaso.cucinotta@santannapisa.it,
	bristot@redhat.com, mathieu.poirier@linaro.org,
	cgroups@vger.kernel.org, peterz@infradead.org, mingo@redhat.com,
	rostedt@goodmis.org
Subject: Re: [PATCH v5 3/5] cgroup/cpuset: make callback_lock raw
Date: Wed, 7 Nov 2018 10:59:34 +0100	[thread overview]
Message-ID: <20181107095934.GX18091@localhost.localdomain> (raw)
In-Reply-To: <20180925143416.GD25664@localhost.localdomain>

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@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
> > 

  reply	other threads:[~2018-11-07  9:59 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-03 14:27 [PATCH v5 0/5] sched/deadline: fix cpusets bandwidth accounting Juri Lelli
2018-09-03 14:27 ` [PATCH v5 1/5] sched/topology: Adding function partition_sched_domains_locked() Juri Lelli
2018-09-03 14:27 ` [PATCH v5 2/5] sched/core: Streamlining calls to task_rq_unlock() Juri Lelli
2018-09-03 14:27 ` [PATCH v5 3/5] cgroup/cpuset: make callback_lock raw Juri Lelli
2018-09-25 14:34   ` Juri Lelli
2018-11-07  9:59     ` Juri Lelli [this message]
2018-11-07 15:53     ` Tejun Heo
2018-11-07 16:38       ` Juri Lelli
2018-11-08 11:22         ` Juri Lelli
2018-11-08 19:11         ` Waiman Long
2018-11-09 10:34           ` Juri Lelli
2018-09-03 14:28 ` [PATCH v5 4/5] sched/core: Prevent race condition between cpuset and __sched_setscheduler() Juri Lelli
2018-10-03 19:42   ` Steven Rostedt
2018-10-04  9:04     ` Juri Lelli
2018-11-08 15:49       ` Waiman Long
2018-11-08 16:23         ` Juri Lelli
2018-09-03 14:28 ` [PATCH v5 5/5] cpuset: Rebuild root domain deadline accounting information Juri Lelli
2018-09-25 12:32   ` Peter Zijlstra
2018-09-25 13:07     ` Juri Lelli
2018-09-25 12:53   ` Peter Zijlstra
2018-09-25 13:08     ` Juri Lelli
2018-09-25  8:14 ` [PATCH v5 0/5] sched/deadline: fix cpusets bandwidth accounting Juri Lelli

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