On 10/10/2011 08:27 PM, Vivek Goyal wrote:
> On Fri, Sep 23, 2011 at 03:52:46PM +0200, Jan Safranek wrote:
>> groups
>>
>> New flag CGFLAG_DELETE_EMPTY_ONLY tells cgroup_delete_cgroup_ext that the
>> group being deleted must be empty, i.e. have no subgroups and no tasks
>> inside.
>>
>> Signed-off-by: Jan Safranek <jsafr...@redhat.com>
>> ---
>>
>> include/libcgroup/groups.h | 7 +++
>> src/api.c | 114
>> +++++++++++++++++++++++++-------------------
>> 2 files changed, 71 insertions(+), 50 deletions(-)
>>
>> diff --git a/include/libcgroup/groups.h b/include/libcgroup/groups.h
>> index 86c5b76..f375a82 100644
>> --- a/include/libcgroup/groups.h
>> +++ b/include/libcgroup/groups.h
>> @@ -26,6 +26,13 @@ enum cgroup_delete_flag {
>> * Recursively delete all child groups.
>> */
>> CGFLAG_DELETE_RECURSIVE = 2,
>> +
>> + /**
>> + * Delete the cgroup only if it is empty, i.e. it has no subgroups and
>> + * no processes inside. This flag cannot be used with
>> + * CGFLAG_DELETE_RECURSIVE.
>> + */
>> + CGFLAG_DELETE_EMPTY_ONLY = 4,
>> };
>>
>> /**
>> diff --git a/src/api.c b/src/api.c
>> index f6f806e..769c080 100644
>> --- a/src/api.c
>> +++ b/src/api.c
>> @@ -1856,30 +1856,33 @@ static int cg_delete_cgroup_controller(char
>> *cgroup_name, char *controller,
>>
>> cgroup_dbg("Removing group %s:%s\n", controller, cgroup_name);
>>
>> - /*
>> - * Open tasks file of the group to delete.
>> - */
>> - if (!cg_build_path(cgroup_name, path, controller))
>> - return ECGROUPSUBSYSNOTMOUNTED;
>> - strncat(path, "tasks", sizeof(path) - strlen(path));
>> -
>> - delete_tasks = fopen(path, "re");
>> - if (delete_tasks) {
>> - ret = cg_move_task_files(delete_tasks, target_tasks);
>> - fclose(delete_tasks);
>> - } else {
>> + if (!(flags & CGFLAG_DELETE_EMPTY_ONLY)) {
>> /*
>
> Will it make sense to introduce a function to check for empty cgroup and
> return if CGFLAG_DELETE_EMPTY_ONLY is set but cgroup is not empty. It
> does involve little extra processing but also makes the code little
> simpler.
The idea here was to let rmdir() if it succeeds or not. Cgroups
infrastructure is inherently racy, there is no way, how to check if a
group is empty and then ensure it stays empty until rmdir().
>
> I think same holds good for other changes in cgroup_delete_cgroup_ext().
>
> Thanks
> Vivek
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