Messages in this thread Patch in this message | | | From | Mandeep Singh Baines <> | Subject | [PATCH] cgroups: fix a css_set not found bug in cgroup_attach_proc | Date | Thu, 15 Dec 2011 11:36:43 -0800 |
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There is a BUG when migrating a PF_EXITING proc. Since css_set_prefetch() is not called for the PF_EXITING case, find_existing_css_set() will return NULL inside cgroup_task_migrate() causing a BUG.
This bug is easy to reproduce. Create a zombie and echo its pid to cgroup.procs.
$ cat zombie.c \#include <unistd.h>
int main() { if (fork()) pause(); return 0; } $
We are hitting this bug pretty regularly on ChromeOS.
This bug is already fixed by Tejun Heo's cgroup patchset which is targetted for the next merge window:
https://lkml.org/lkml/2011/11/1/356
I've create a smaller patch here which just fixes this bug so that a fix can be merged into the current release and stable.
Signed-off-by: Mandeep Singh Baines <msb@chromium.org> Downstream-Bug-Report: http://crosbug.com/23953 Cc: Tejun Heo <tj@kernel.org> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: containers@lists.linux-foundation.org Cc: cgroups@vger.kernel.org Cc: stable@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> Cc: Olof Johansson <olofj@chromium.org> --- kernel/cgroup.c | 5 ----- 1 files changed, 0 insertions(+), 5 deletions(-)
diff --git a/kernel/cgroup.c b/kernel/cgroup.c index d9d5648..a184470 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -2098,11 +2098,6 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader) continue; /* get old css_set pointer */ task_lock(tsk); - if (tsk->flags & PF_EXITING) { - /* ignore this task if it's going away */ - task_unlock(tsk); - continue; - } oldcg = tsk->cgroups; get_css_set(oldcg); task_unlock(tsk); -- 1.7.3.1
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