diff options
| author | Li Zefan <lizf@cn.fujitsu.com> | 2008-11-12 13:26:49 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2008-11-12 17:17:16 -0800 |
| commit | 687446760bd008df96655cb8c5900f8e48a7118c (patch) | |
| tree | b4834a1e88d98234cfad90a0880b54ba1cc3cc59 /kernel/cgroup_freezer.c | |
| parent | 0bcb6069a6e1af5c114a2a8873ec43ada8933596 (diff) | |
| download | lwn-687446760bd008df96655cb8c5900f8e48a7118c.tar.gz lwn-687446760bd008df96655cb8c5900f8e48a7118c.zip | |
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 <lizf@cn.fujitsu.com>
Cc: Matt Helsley <matthltc@us.ibm.com>
Cc: Cedric Le Goater <clg@fr.ibm.com>
Cc: "Serge E. Hallyn" <serue@us.ibm.com>
Cc: Paul Menage <menage@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/cgroup_freezer.c')
| -rw-r--r-- | 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 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); |