lkml.org 
[lkml]   [2011]   [Aug]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[PATCH v2] cgroups: Don't attach task to subsystem if migration failed
On Thu, Aug 25, 2011 at 01:44:36PM -0700, akpm@linux-foundation.org wrote:
>
> The patch titled
> cgroups: fix ordering of calls in cgroup_attach_proc
> has been added to the -mm tree. Its filename is
> cgroups-fix-ordering-of-calls-in-cgroup_attach_proc.patch
>
> Before you just go and hit "reply", please:
> a) Consider who else should be cc'ed
> b) Prefer to cc a suitable mailing list as well
> c) Ideally: find the original patch on the mailing list and do a
> reply-to-all to that, adding suitable additional cc's
>
> *** Remember to use Documentation/SubmitChecklist when testing your code ***
>
> See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find
> out what to do about this
>
> The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
>
> ------------------------------------------------------
> Subject: cgroups: fix ordering of calls in cgroup_attach_proc
> From: Ben Blum <bblum@andrew.cmu.edu>
>
> awaiting useful changelog...
>

Here is the patch with a (trial of a) useful changelog. Subject
has been changed as well:

---
From a9b84e395a0355cd1aa5ee0f525cd682b16dad63 Mon Sep 17 00:00:00 2001
From: Ben Blum <bblum@andrew.cmu.edu>
Date: Thu, 25 Aug 2011 13:44:36 -0700
Subject: [PATCH] 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>
---
kernel/cgroup.c | 15 +++++++++------
1 files changed, 9 insertions(+), 6 deletions(-)
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 1d2b6ce..84bdace 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -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. */

--
1.7.5.4



\
 
 \ /
  Last update: 2011-08-26 17:41    [from the cache]
©2003-2011 Jasper Spaans