From: Li Zefan <lizefan@huawei.com>
To: Tejun Heo <tj@kernel.org>
Cc: Al Viro <viro@ZenIV.linux.org.uk>,
LKML <linux-kernel@vger.kernel.org>,
Cgroups <cgroups@vger.kernel.org>
Subject: Re: [PATCH 2/3] cgroup: add cgroup_name() API
Date: Tue, 26 Feb 2013 18:25:08 +0800 [thread overview]
Message-ID: <512C8D84.7090707@huawei.com> (raw)
In-Reply-To: <20130226022703.GA13837@htj.dyndns.org>
On 2013/2/26 10:27, Tejun Heo wrote:
> On Mon, Feb 25, 2013 at 02:17:49PM +0800, Li Zefan wrote:
>> cgroup_name() returns the name of a cgroup and it must be called with
>> rcu_read_lock() held.
>>
>> This will be used by cpuset.
>>
>> Signed-off-by: Li Zefan <lizefan@huawei.com>
> ...
>> /**
>> + * cgroup_name - get the name of a cgroup
>> + * @cgrp: the cgroup in question
>> + *
>> + * Must be called with rcu_read_lock() held.
>> + */
>> +char *cgroup_name(const struct cgroup *cgrp)
>> +{
>> + if (!cgrp->parent)
>> + return "/";
>> + else
>> + return rcu_dereference(cgrp->name)->name;
>> +}
>
> Can't we initialize ->name of root cgroup to "/" and lose the
> conditional?
Sure we can. We'll have to allocate cgrp->name in cgroup_remount() and
cgroup_init(), and free cgrp->name in cgroup_kill_sb(). It looks to me
the current version is a bit simpler.
That said, I don't have strong preference. I'll revise the patchset if
you still prefer to init root_cgrp->name.
> We can lose the wrapper altogether but if you're worried
> that sparse check isn't enough, we can have trivial inline wrapper,
> but in that case it probably would help to rename cgrp->name to, say,
> cgrp->__name and put a comment directing people to the accessing
> wrapper which should probably return const char *.
>
I do expect people always use cgroup_name(). Should anyone access
cgrp->name directly and doesn't notice cgrp->name can be NULL, he'll
get NULL ptr crash and turn to cgroup_name(), and a comment to guide
people to cgroup_name() is helpful too.
next prev parent reply other threads:[~2013-02-26 10:25 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-02-25 6:17 [PATCH v3 1/3] cgroup: fix cgroup_path() vs rename() race Li Zefan
2013-02-25 6:17 ` [PATCH 2/3] cgroup: add cgroup_name() API Li Zefan
2013-02-26 2:27 ` Tejun Heo
2013-02-26 10:25 ` Li Zefan [this message]
2013-02-26 13:26 ` Tejun Heo
2013-02-27 10:49 ` Li Zefan
2013-02-27 13:23 ` Tejun Heo
2013-02-28 6:53 ` Li Zefan
2013-02-28 14:49 ` Tejun Heo
2013-03-01 6:36 ` Li Zefan
2013-03-01 20:39 ` Al Viro
2013-03-01 20:45 ` Tejun Heo
2013-03-04 3:02 ` Li Zefan
2013-03-04 17:38 ` Tejun Heo
2013-02-25 6:18 ` [PATCH 3/3] cpuset: use cgroup_name() in cpuset_print_task_mems_allowed() Li Zefan
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