On Mon, Jun 24, 2013 at 04:20:51PM -0700, Tim Chen wrote:
> +#ifdef CONFIG_RWSEM_SPIN_ON_WRITE_OWNER
> +static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem)
> +{
> + int retval;
> + task_struct *owner;
> +
> + rcu_read_lock();
> + owner = sem->owner;
That wants to be: owner = ACCESS_ONCE(sem->owner);
> +
> + /* Spin only if active writer running */
> + if (owner)
> + retval = owner->on_cpu;
> + else
> + retval = false;
> +
> + rcu_read_unlock();
> + /*
> + * if lock->owner is not set, the sem owner may have just acquired
> + * it and not set the owner yet, or the sem has been released, or
> + * reader active.
> + */
> + return retval;
> +}
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