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