Re: [PATCH 4/5] cgroup: remove extra calls to find_existing_css_set

From: Tejun Heo
Date: Tue Dec 20 2011 - 18:30:57 EST


Hello,

On Tue, Dec 20, 2011 at 03:14:32PM -0800, Mandeep Singh Baines wrote:
> @@ -1942,9 +1917,17 @@ int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
> }
> }
>
> - retval = cgroup_task_migrate(cgrp, oldcgrp, tsk, false);
> - if (retval)
> + task_lock(tsk);
> + oldcg = tsk->cgroups;
> + task_unlock(tsk);

Probably this is patch order issue w/ Frederic's patch but we don't
need task_lock here, right?

> @@ -2171,17 +2088,18 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
> * step 2: make sure css_sets exist for all threads to be migrated.
> * we use find_css_set, which allocates a new one if necessary.
> */
> - INIT_LIST_HEAD(&newcg_list);
> for (i = 0; i < group_size; i++) {
> tc = flex_array_get(group, i);
> /* get old css_set pointer */
> task_lock(tc->task);
> oldcg = tc->task->cgroups;
> task_unlock(tc->task);
> - /* if we don't already have it in the list get a new one */
> - if (!css_set_fetched(cgrp, tc->task, oldcg, &newcg_list))
> - if (retval = css_set_prefetch(cgrp, oldcg, &newcg_list))
> - goto out_list_teardown;
> + tc->cg = find_css_set(oldcg, cgrp);
> + if (!tc->cg) {
> + retval = -ENOMEM;
> + css_set_refs = i + 1;
> + goto out_list_teardown;
> + }

Nice cleanup, but can't the above be merged into the loop which builds
the flex array?

Thanks.

--
tejun
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