From: Zhang Qiao <zhangqiao22@huawei.com>
To: Waiman Long <longman@redhat.com>, <linux-kernel@vger.kernel.org>,
<cgroups@vger.kernel.org>
Cc: <tj@kernel.org>, <lizefan.x@bytedance.com>, <hannes@cmpxchg.org>,
<matthltc@us.ibm.com>, <bblum@google.com>, <menage@google.com>,
<akpm@linux-foundation.org>, <mkoutny@suse.com>,
<zhaogongyi@huawei.com>
Subject: Re: [PATCH] cgroup/cpuset: Fix a race between cpuset_attach() and cpu hotplug
Date: Sat, 22 Jan 2022 15:54:09 +0800 [thread overview]
Message-ID: <12975f48-0419-9c34-8751-c3d3fca4f7b3@huawei.com> (raw)
In-Reply-To: <a166a39f-aa9f-95af-3f3f-f4e17e7c3305@redhat.com>
在 2022/1/21 20:43, Waiman Long 写道:
> On 1/21/22 05:12, Zhang Qiao wrote:
>> As previously discussed(https://lkml.org/lkml/2022/1/20/51),
>> cpuset_attach() is affected with similar cpu hotplug race,
>> as follow scenario:
>>
>> cpuset_attach() cpu hotplug
>> --------------------------- ----------------------
>> down_write(cpuset_rwsem)
>> guarantee_online_cpus() // (load cpus_attach)
>> sched_cpu_deactivate
>> set_cpu_active()
>> // will change cpu_active_mask
>> set_cpus_allowed_ptr(cpus_attach)
>> __set_cpus_allowed_ptr_locked()
>> // (if the intersection of cpus_attach and
>> cpu_active_mask is empty, will return -EINVAL)
>> up_write(cpuset_rwsem)
>>
>> To avoid races such as described above, protect cpuset_attach() call
>> with cpu_hotplug_lock.
>>
>> Fixes: be367d099270 ("cgroups: let ss->can_attach and ss->attach do whole threadgroups at a time")
>> Reported-by: Zhao Gongyi <zhaogongyi@huawei.com>
>> Signed-off-by: Zhang Qiao <zhangqiao22@huawei.com>
>> ---
>> kernel/cgroup/cpuset.c | 2 ++
>> 1 file changed, 2 insertions(+)
>>
>> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
>> index dc653ab26e50..0af5725cc1df 100644
>> --- a/kernel/cgroup/cpuset.c
>> +++ b/kernel/cgroup/cpuset.c
>> @@ -2252,6 +2252,7 @@ static void cpuset_attach(struct cgroup_taskset *tset)
>> cgroup_taskset_first(tset, &css);
>> cs = css_cs(css);
>>
>> + cpus_read_lock();
>> percpu_down_write(&cpuset_rwsem);
>>
>> guarantee_online_mems(cs, &cpuset_attach_nodemask_to);
>> @@ -2305,6 +2306,7 @@ static void cpuset_attach(struct cgroup_taskset *tset)
>> wake_up(&cpuset_attach_wq);
>>
>> percpu_up_write(&cpuset_rwsem);
>> + cpus_read_unlock();
>> }
>>
>> /* The various types of files and directories in a cpuset file system */
>> --
>> 2.18.0
>
> The locking sequence looks right.
>
> Acked-by: Waiman Long <longman@redhat.com>
>
Thanks for your review!
Regards,
Qiao
.
> .
next prev parent reply other threads:[~2022-01-22 7:54 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-21 10:12 [PATCH] cgroup/cpuset: Fix a race between cpuset_attach() and cpu hotplug Zhang Qiao
2022-01-21 12:43 ` Waiman Long
2022-01-22 7:54 ` Zhang Qiao [this message]
2022-01-21 15:57 ` Michal Koutný
2022-01-22 7:37 ` Zhang Qiao
2022-02-07 6:17 ` Zhang Qiao
2022-02-14 19:50 ` Tejun Heo
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