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SubjectRe: [RFC] [PATCH] cgroup: add "procs" control file
KAMEZAWA Hiroyuki wrote:
> On Wed, 18 Jun 2008 16:02:25 +0800
> Li Zefan <lizf@cn.fujitsu.com> wrote:
>
>> This control file is the equivalent of the "tasks" control file, but
>> acting/reporting on entire thread groups.
>>
>> For example, we have a process with pid 1000 and its sub-thread with
>> tid 1001, to attach them into a cgroup:
>> # echo 1000 > procs
>> Then show the process list and the task list respectively:
>> # cat procs
>> 1000
>> # cat tasks
>> 1000
>> 1001
>>
>> Questions:
>> - What to do if the attaching of a thread failed? continue to attach
>> other threads, or stop and return error?
>> - When a sub-thread of a process is in the cgroup, but not its thread
>> cgroup leader, what to do when 'cat procs'? just skip those threads?
>>
> I think this feature make sense. But not meets a theory that cgroup handles
> a thread not a process. So, how about changing the definition of this interface
> from
> - showing procs
> to
> - showing threads which is thread-group-leader.
>
> One possible problem is a case that thread-group-leader exits while other
> members are alive. In such case, thread-group-leader calls cgroup_exit()
> but will be still alive until all sub-threads exit. So, this interface
> cannot show correct information.
> (right ??? please point out if I miss something)
>

It can show the thread group leader in zombie state with [TID]?

> So, how about this kind of interface ? showing both of TID and PID.
>
> %/cat/procs
> TID PID
> 1001 1001
> 1234 1001
> 3856 1001
> 728 728
> ....
> ....
>
> nonsense ?

This information is also available from other means /proc/pid/tasks for example.
I like Li's original interface for procs and tasks. I would also suggest adding
groups.

--
Warm Regards,
Balbir Singh
Linux Technology Center
IBM, ISTL


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