diff options
| author | Tejun Heo <tj@kernel.org> | 2012-10-18 17:40:30 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2012-10-28 10:14:14 -0700 |
| commit | 5993bba302a1a6df9c73690a08346411ff7cd56e (patch) | |
| tree | d10d70343dd1df236e6d16d75de9c107c86f82d1 /kernel | |
| parent | 9a55fef20afb3d7362b0c9d19ba1e78dfe482d3d (diff) | |
Revert "cgroup: Remove task_lock() from cgroup_post_fork()"
commit d87838321124061f6c935069d97f37010fa417e6 upstream.
This reverts commit 7e3aa30ac8c904a706518b725c451bb486daaae9.
The commit incorrectly assumed that fork path always performed
threadgroup_change_begin/end() and depended on that for
synchronization against task exit and cgroup migration paths instead
of explicitly grabbing task_lock().
threadgroup_change is not locked when forking a new process (as
opposed to a new thread in the same process) and even if it were it
wouldn't be effective as different processes use different threadgroup
locks.
Revert the incorrect optimization.
Signed-off-by: Tejun Heo <tj@kernel.org>
LKML-Reference: <20121008020000.GB2575@localhost>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/cgroup.c | 15 |
1 files changed, 3 insertions, 12 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c index b76dd5862a8c..5cb488065dca 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -4539,19 +4539,10 @@ void cgroup_post_fork(struct task_struct *child) */ if (use_task_css_set_links) { write_lock(&css_set_lock); - if (list_empty(&child->cg_list)) { - /* - * It's safe to use child->cgroups without task_lock() - * here because we are protected through - * threadgroup_change_begin() against concurrent - * css_set change in cgroup_task_migrate(). Also - * the task can't exit at that point until - * wake_up_new_task() is called, so we are protected - * against cgroup_exit() setting child->cgroup to - * init_css_set. - */ + task_lock(child); + if (list_empty(&child->cg_list)) list_add(&child->cg_list, &child->cgroups->tasks); - } + task_unlock(child); write_unlock(&css_set_lock); } } |