Commit 77ceab8e authored Nov 02, 2011 by Ben Blum Committed by Linus Torvalds Nov 02, 2011

cgroups: don't attach task to subsystem if migration failed



If a task has exited to the point it has called cgroup_exit() already,
then we can't migrate it to another cgroup anymore.

This can happen when we are attaching a task to a new cgroup between the
call to ->can_attach_task() on subsystems and the migration that is
eventually tried in cgroup_task_migrate().

In this case cgroup_task_migrate() returns -ESRCH and we don't want to
attach the task to the subsystems because the attachment to the new cgroup
itself failed.

Fix this by only calling ->attach_task() on the subsystems if the cgroup
migration succeeded.

Reported-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Ben Blum <bblum@andrew.cmu.edu>
Acked-by: Paul Menage <paul@paulmenage.org>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 33ef6b69

kernel/cgroup.c

+9 −6

Original line number	Diff line number	Diff line
		@@ -2135,14 +2135,17 @@ int cgroup_attach_proc(struct cgroup cgrp, struct task_struct leader)
		oldcgrp = task_cgroup_from_root(tsk, root);
		if (cgrp == oldcgrp)
		continue;
		/* if the thread is PF_EXITING, it can just get skipped. */
		retval = cgroup_task_migrate(cgrp, oldcgrp, tsk, true);
		if (retval == 0) {
		/* attach each task to each subsystem */
		for_each_subsys(root, ss) {
		if (ss->attach_task)
		ss->attach_task(cgrp, tsk);
		}
		/* if the thread is PF_EXITING, it can just get skipped. */
		retval = cgroup_task_migrate(cgrp, oldcgrp, tsk, true);
		BUG_ON(retval != 0 && retval != -ESRCH);
		} else {
		BUG_ON(retval != -ESRCH);
		}
		}
		/* nothing is sensitive to fork() after this point. */

Admin message