On Fri, Aug 26, 2011 at 12:43:12AM +0200, Tejun Heo wrote:
> diff --git a/kernel/cgroup.c b/kernel/cgroup.c
> index f3c7f7a..ce765ec 100644
> --- a/kernel/cgroup.c
> +++ b/kernel/cgroup.c
> @@ -2075,7 +2064,6 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
> {
> int retval, i, group_size, nr_migrating_tasks;
> struct cgroup_subsys *ss, *failed_ss = NULL;
> - bool cancel_failed_ss = false;
> /* guaranteed to be initialized later, but the compiler needs this */
> struct css_set *oldcg;
> struct cgroupfs_root *root = cgrp->root;
> @@ -2166,21 +2154,6 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
> goto out_cancel_attach;
> }
> }
> - /* a callback to be run on every thread in the threadgroup. */
> - if (ss->can_attach_task) {
> - /* run on each task in the threadgroup. */
> - for (i = 0; i < group_size; i++) {
> - tc = flex_array_get(group, i);
> - if (tc->cgrp == cgrp)
> - continue;
> - retval = ss->can_attach_task(cgrp, tc->task);
> - if (retval) {
> - failed_ss = ss;
> - cancel_failed_ss = true;
> - goto out_cancel_attach;
> - }
> - }
> - }
> }
>
> /*
> @@ -2217,15 +2190,10 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
> }
>
> /*
> - * step 3: now that we're guaranteed success wrt the css_sets, proceed
> - * to move all tasks to the new cgroup, calling ss->attach_task for each
> - * one along the way. there are no failure cases after here, so this is
> - * the commit point.
> + * step 3: now that we're guaranteed success wrt the css_sets,
> + * proceed to move all tasks to the new cgroup. There are no
> + * failure cases after here, so this is the commit point.
> */
> - for_each_subsys(root, ss) {
> - if (ss->pre_attach)
> - ss->pre_attach(cgrp);
> - }
> for (i = 0; i < group_size; i++) {
> tc = flex_array_get(group, i);
> /* leave current thread as it is if it's already there */
> @@ -2235,19 +2203,11 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
> /* if the thread is PF_EXITING, it can just get skipped. */
> retval = cgroup_task_migrate(cgrp, tc->cgrp, tc->task, true);
> BUG_ON(retval != 0 && retval != -ESRCH);
> -
> - /* attach each task to each subsystem */
> - for_each_subsys(root, ss) {
> - if (ss->attach_task)
> - ss->attach_task(cgrp, tc->task);
> - }
In order to keep the fix queued in -mm (https://lkml.org/lkml/2011/8/26/262)
the tasks that have failed to migrate should be removed from the iterator
so that they are not included in the batch in ->attach().
> }
> /* nothing is sensitive to fork() after this point. */
>
> /*
> - * step 4: do expensive, non-thread-specific subsystem callbacks.
> - * TODO: if ever a subsystem needs to know the oldcgrp for each task
> - * being moved, this call will need to be reworked to communicate that.
> + * step 4: do subsystem attach callbacks.
> */
> for_each_subsys(root, ss) {
> if (ss->attach)
> @@ -2271,11 +2231,8 @@ out_cancel_attach:
> /* same deal as in cgroup_attach_task */
> if (retval) {
> for_each_subsys(root, ss) {
> - if (ss == failed_ss) {
> - if (cancel_failed_ss && ss->cancel_attach)
> - ss->cancel_attach(ss, cgrp, &tset);
> + if (ss == failed_ss)
> break;
> - }
> if (ss->cancel_attach)
> ss->cancel_attach(ss, cgrp, &tset);
> }
> --
> 1.7.6
>
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