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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>
This commit is contained in:
Ben Blum 2011-11-02 13:38:07 -07:00 committed by Linus Torvalds
parent 33ef6b6984
commit 77ceab8ea5
1 changed files with 9 additions and 6 deletions
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15
kernel/cgroup.c
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@ -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;
/* 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);
if (retval == 0) {
/* attach each task to each subsystem */
for_each_subsys(root, ss) {
if (ss->attach_task)
ss->attach_task(cgrp, tsk);
}
} else {
BUG_ON(retval != -ESRCH);
}
}
/* nothing is sensitive to fork() after this point. */