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    SubjectRe: [PATCH] kthread_worker: Initialize dynamically allocated spinlock properly for lockdep
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    On Sun, Dec 19, 2010 at 8:49 PM, Andy Walls <awalls@md.metrocast.net> wrote:
    > init_kthread_worker(), via KTHREAD_WORKER_INIT(), used an
    > initializer for static spin_lock objects, SPIN_LOCK_UNLOCKED, on
    > a dynamically allocated kthread_worker object's internal spinlock_t.
    > This causes lockdep to gripe:
    >
    >        INFO: trying to register non-static key.
    >        the code is fine but needs lockdep annotation.
    >        turning off the locking correctness validator.
    >
    > To keep lockdep happy, use spin_lock_init() for dynamically
    > allocated kthread_worker objects' internal spinlock_t.
    >
    > Reported-by: Nicolas <nicolas.mailhot@laposte.net>
    > Signed-off-by: Andy Walls <awalls@md.metrocast.net>
    >
    > Cc: Tejun Heo <tj@kernel.org>
    > Cc: Jarod Wilson <jarod@redhat.com>
    > Cc: Ingo Molnar <mingo@redhat.com>
    > Cc: Mauro Carvalho Chehab <mchehab@redhat.com>
    > Cc: Hans Verkuil <hverkuil@xs4all.nl>
    >
    > diff --git a/include/linux/kthread.h b/include/linux/kthread.h
    > index 685ea65..e65d0b1 100644
    > --- a/include/linux/kthread.h
    > +++ b/include/linux/kthread.h
    > @@ -83,7 +83,13 @@ struct kthread_work {
    >
    >  static inline void init_kthread_worker(struct kthread_worker *worker)
    >  {
    > -       *worker = (struct kthread_worker)KTHREAD_WORKER_INIT(*worker);
    > +       /*
    > +        * Lockdep complains if a dynamically allocated worker's spinlock_t
    > +        * is initialzed using SPIN_LOCK_UNLOCKED.
    > +        */
    > +       spin_lock_init(&worker->lock);

    This will make different kthead_worker->lock initialized with one same
    key. You know spin_lock_init() will be like below:
    # define raw_spin_lock_init(lock) \
    do { \
    static struct lock_class_key __key; \
    \
    __raw_spin_lock_init((lock), #lock, &__key); \
    } while (0)

    So we should put the real initializer to kernel/kthread.c
    and make init_kthread_worker() to be a MACRO.

    BTW, init_kthread_work() should also be changed like above
    because member done is a wait_queue_head.

    Thanks,
    Yong

    --
    Only stand for myself.
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