From: Juri Lelli <juri.lelli@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: mingo@redhat.com, rostedt@goodmis.org, tj@kernel.org,
linux-kernel@vger.kernel.org, luca.abeni@santannapisa.it,
claudio@evidence.eu.com, tommaso.cucinotta@santannapisa.it,
bristot@redhat.com, mathieu.poirier@linaro.org,
lizefan@huawei.com, cgroups@vger.kernel.org
Subject: Re: [PATCH v6 3/5] cgroup/cpuset: make callback_lock raw
Date: Tue, 5 Feb 2019 10:18:20 +0100 [thread overview]
Message-ID: <20190205091820.GE30905@localhost.localdomain> (raw)
In-Reply-To: <20190204120711.GA17582@hirez.programming.kicks-ass.net>
On 04/02/19 13:07, Peter Zijlstra wrote:
> On Mon, Feb 04, 2019 at 01:02:36PM +0100, Peter Zijlstra wrote:
> > On Thu, Jan 17, 2019 at 09:47:37AM +0100, Juri Lelli wrote:
> > > @@ -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;
> > > }
> >
> > These three appear to be a user-controlled O(n) (depth of cgroup tree).
> > Which is basically bad for raw_spinlock_t.
> >
> > The Changelog should really have mentioned this; and ideally we'd
> > somehow avoid this.
>
> N/m avoiding it; we have this all over the place, just mention it..
OK.
next prev parent reply other threads:[~2019-02-05 9:18 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-17 8:47 [PATCH v6 0/5] sched/deadline: fix cpusets bandwidth accounting Juri Lelli
2019-01-17 8:47 ` [PATCH v6 1/5] sched/topology: Adding function partition_sched_domains_locked() Juri Lelli
2019-01-17 8:47 ` [PATCH v6 2/5] sched/core: Streamlining calls to task_rq_unlock() Juri Lelli
2019-01-17 8:47 ` [PATCH v6 3/5] cgroup/cpuset: make callback_lock raw Juri Lelli
2019-02-04 11:55 ` Peter Zijlstra
2019-02-05 9:18 ` Juri Lelli
2019-02-04 12:02 ` Peter Zijlstra
2019-02-04 12:07 ` Peter Zijlstra
2019-02-05 9:18 ` Juri Lelli [this message]
2019-01-17 8:47 ` [PATCH v6 4/5] sched/core: Prevent race condition between cpuset and __sched_setscheduler() Juri Lelli
2019-02-04 12:10 ` Peter Zijlstra
2019-02-05 9:51 ` Juri Lelli
2019-02-05 11:20 ` Peter Zijlstra
2019-02-05 11:49 ` Juri Lelli
2019-01-17 8:47 ` [PATCH v6 5/5] cpuset: Rebuild root domain deadline accounting information Juri Lelli
2019-01-18 16:17 ` [PATCH v6 0/5] sched/deadline: fix cpusets bandwidth accounting Tejun Heo
2019-01-18 16:46 ` Juri Lelli
2019-02-04 9:02 ` Juri Lelli
2019-02-04 12:18 ` Peter Zijlstra
2019-02-04 18:45 ` Waiman Long
2019-02-05 9:18 ` Juri Lelli
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