Re: [PATCH -mm 4/5][AIO] - AIO completion signal notification

["Sébastien Dugué" <sebastien.dugue@bull.net>]

On Tue, 23 Jan 2007 21:35:13 -0800 Andrew Morton <akpm@osdl.org> wrote:

> On Wed, 17 Jan 2007 10:50:18 +0100
> Sébastien Dugué <sebastien.dugue@bull.net> wrote:
> 
> > +static long aio_setup_sigevent(struct aio_notify *notify,
> > +			       struct sigevent __user *user_event)
> > +{
> > +	sigevent_t event;
> > +	struct task_struct *target;
> > +
> > +	if (copy_from_user(&event, user_event, sizeof (event)))
> > +		return -EFAULT;
> > +
> > +	if (event.sigev_notify == SIGEV_NONE)
> > +		return 0;
> > +
> > +	notify->notify = event.sigev_notify;
> > +	notify->signo = event.sigev_signo;
> > +	notify->value = event.sigev_value;
> > +
> > +	read_lock(&tasklist_lock);
> > +	target = good_sigevent(&event);
> > +
> > +	if (unlikely(!target || (target->flags & PF_EXITING)))
> > +		goto out_unlock;
> > +
> > +	/*
> > +	 * At this point, we know that notify is either SIGEV_SIGNAL or
> > +	 * SIGEV_THREAD_ID and the target task is valid. So get a reference
> > +	 * on the task, it will be dropped in really_put_req() when
> > +	 * we're done with the request.
> > +	 */
> > +	get_task_struct(target);
> > +	notify->target = target;
> > +	read_unlock(&tasklist_lock);
> > +
> > +	/*
> > +	 * NOTE: we cannot free the sigqueue in the completion path as
> > +	 * the signal may not have been delivered to the target task.
> > +	 * Therefore it has to be freed in __sigqueue_free() when the
> > +	 * signal is collected if si_code is SI_ASYNCIO.
> > +	 */
> > +	notify->sigq = sigqueue_alloc();
> > +
> > +	if (unlikely(!notify->sigq))
> > +		return -EAGAIN;
> 
> Did this just leak a ref on the task_struct?
> 

  No, the ref is released in really_put_req() when we dispose of
the iocb.

  Thanks,

  Sébastien.