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    SubjectRe: [PATCH 6/6] cls_cgroup: remove redundant rcu_read_lock/unlock
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    Le mercredi 01 février 2012 à 14:56 +0800, Li Zefan a écrit :
    > We've already used rcu_read_lock/unlock inside task_classid(),
    > so don't use the lock/unlock pair twice in this hot path.
    >
    > Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
    > ---
    > net/core/sock.c | 2 --
    > 1 files changed, 0 insertions(+), 2 deletions(-)
    >
    > diff --git a/net/core/sock.c b/net/core/sock.c
    > index 213c856..c0bab23 100644
    > --- a/net/core/sock.c
    > +++ b/net/core/sock.c
    > @@ -1160,9 +1160,7 @@ void sock_update_classid(struct sock *sk)
    > {
    > u32 classid;
    >
    > - rcu_read_lock(); /* doing current task, which cannot vanish. */
    > classid = task_cls_classid(current);
    > - rcu_read_unlock();
    > if (classid && classid != sk->sk_classid)
    > sk->sk_classid = classid;

    Yes, this seems fine.

    Then, I wonder why we do the "if (classid && classid != sk->sk_classid)"

    before the :

    sk->sk_classid = classid;

    This seems unnecessary checks.


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