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authorMandeep Singh Baines <msb@chromium.org>2011-12-15 11:36:43 -0800
committerTejun Heo <tj@kernel.org>2011-12-19 09:09:09 -0800
commite0197aae59e55c06db172bfbe1a1cdb8c0e1cab3 (patch)
treec3b36f2adc445893166bc5caddb3d26c05611a9a
parent390f998509bf049019df0b078c0a6606e0d57fb4 (diff)
cgroups: fix a css_set not found bug in cgroup_attach_proc
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 Reviewed-by: Li Zefan <lizf@cn.fujitsu.com> Signed-off-by: Tejun Heo <tj@kernel.org> 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>
-rw-r--r--kernel/cgroup.c5
1 files changed, 0 insertions, 5 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index d9d5648f3cdc..a184470cf9b5 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);