Messages in this thread Patch in this message | | | Date | Tue, 04 Nov 2008 14:48:39 +0800 | From | Li Zefan <> | Subject | [PATCH] freezer_cg: remove task_lock from freezer_fork() |
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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 <lizf@cn.fujitsu.com> --- kernel/cgroup_freezer.c | 8 ++++++-- 1 files changed, 6 insertions(+), 2 deletions(-)
diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c index 7fa476f..6605907 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); -- 1.5.4.rc3
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