From 687446760bd008df96655cb8c5900f8e48a7118c Mon Sep 17 00:00:00 2001 From: Li Zefan Date: Wed, 12 Nov 2008 13:26:49 -0800 Subject: freezer_cg: remove task_lock from freezer_fork() In theory the task can be moved to another cgroup and the freezer will be freed right after task_lock is dropped, so the lock results in zero protection. But in the case of freezer_fork() no lock is needed, since the task is not in tasklist yet so it won't be moved to another cgroup, so task->cgroups won't be changed or invalidated. Signed-off-by: Li Zefan Cc: Matt Helsley Cc: Cedric Le Goater Cc: "Serge E. Hallyn" Cc: Paul Menage Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/cgroup_freezer.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c index 7fa476f01d05..660590710409 100644 --- a/kernel/cgroup_freezer.c +++ b/kernel/cgroup_freezer.c @@ -184,9 +184,13 @@ static void freezer_fork(struct cgroup_subsys *ss, struct task_struct *task) { struct freezer *freezer; - task_lock(task); + /* + * No lock is needed, since the task isn't on tasklist yet, + * so it can't be moved to another cgroup, which means the + * freezer won't be removed and will be valid during this + * function call. + */ freezer = task_freezer(task); - task_unlock(task); spin_lock_irq(&freezer->lock); BUG_ON(freezer->state == CGROUP_FROZEN); -- cgit v1.2.3