Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit b07ef774 authored by Mandeep Singh Baines's avatar Mandeep Singh Baines Committed by Tejun Heo
Browse files

cgroup: remove redundant get/put of task struct 

threadgroup_lock() guarantees that the target threadgroup will
remain stable - no new task will be added, no new PF_EXITING
will be set and exec won't happen.

Changes in V2:
* https://lkml.org/lkml/2011/12/20/369

 (Tejun Heo)
  * Undo incorrect removal of get/put from attach_task_by_pid()
* Author
  * Remove a comment which is made stale by this change

Signed-off-by: default avatarMandeep Singh Baines <msb@chromium.org>
Acked-by: default avatarLi Zefan <lizf@cn.fujitsu.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Cc: containers@lists.linux-foundation.org
Cc: cgroups@vger.kernel.org
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul Menage <paul@paulmenage.org>
parent 026085ef

kernel/cgroup.c

+2 −9
Original line number Diff line number Diff line
@@ -2116,7 +2116,7 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader) 
		retval = -EAGAIN;

		goto out_free_group_list;

	}

	/* take a reference on each task in the group to go in the array. */



	tsk = leader;

	i = nr_migrating_tasks = 0;

	do {
@@ -2128,7 +2128,6 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader) 


		/* as per above, nr_threads may decrease, but not increase. */

		BUG_ON(i >= group_size);

		get_task_struct(tsk);

		/*

		 * saying GFP_ATOMIC has no effect here because we did prealloc

		 * earlier, but it's good form to communicate our expectations.
@@ -2150,7 +2149,7 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader) 
	/* methods shouldn't be called if no task is actually migrating */

	retval = 0;

	if (!nr_migrating_tasks)

		goto out_put_tasks;

		goto out_free_group_list;



	/*

	 * step 1: check that we can legitimately attach to the cgroup.
@@ -2234,12 +2233,6 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader) 
				ss->cancel_attach(ss, cgrp, &tset);

		}

	}

out_put_tasks:

	/* clean up the array of referenced threads in the group. */

	for (i = 0; i < group_size; i++) {

		tc = flex_array_get(group, i);

		put_task_struct(tc->task);

	}

out_free_group_list:

	flex_array_free(group);

	return retval;