linux-kernel - Re: [PATCH -mm 3/3][AIO] - AIO completion signal notification

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Date:	Fri, 10 Nov 2006 10:20:37 +0100
From:	Sébastien Dugué <sebastien.dugue@...l.net>
To:	Badari Pulavarty <pbadari@...il.com>
Cc:	Christoph Hellwig <hch@...radead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Suparna Bhattacharya <suparna@...ibm.com>,
	Ulrich Drepper <drepper@...hat.com>,
	Zach Brown <zach.brown@...cle.com>,
	Dave Jones <davej@...hat.com>,
	Jean Pierre Dion <jean-pierre.dion@...l.net>,
	"linux-aio@...ck.org" <linux-aio@...ck.org>
Subject: Re: [PATCH -mm 3/3][AIO] - AIO completion signal notification

On Thu, 2006-11-09 at 11:27 -0800, Badari Pulavarty wrote:
> On Thu, 2006-11-09 at 19:08 +0000, Christoph Hellwig wrote:
> 
> Looks much better :)

  Indeed ;-)

> 
> > 
> > static long aio_setup_sigevent(struct kiocb *iocb,
> > 			       struct sigevent __user *user_event)
> > {
> > 	sigevent_t event;
> > 	struct task_struct *target;
> > 	unsigned long flags;
> > 
> > 	if (copy_from_user(&event, user_event, sizeof (event)))
> > 		return -EFAULT;
> > 
> > 	if (event.sigev_notify == SIGEV_NONE)
> > 		return 0;
> > 
> > 	iocb->ki_notify.notify = event.sigev_notify;
> 
> Don't we want to verify to make sure that we are accepting only
> SIGEV_SIGNAL or SIGEV_THREAD_ID and return -EINVAL, if some
> one passes invalid event ? Like
> 
> 	if ((event.sigev_notify != SIGEV_SIGNAL) &&
> 		(event.sigev_notify != SIGEV_THREAD_ID)) 
> 		return -EINVAL;

  That check is done in good_sigevent() below.

> 
> > 	iocb->ki_notify.signo = event.sigev_signo;
> > 	iocb->ki_notify.value = event.sigev_value;
> > 
> > 	read_lock(&tasklist_lock);
> > 	target = good_sigevent(&event);
> > 	if (unlikely(!target || (target->flags & PF_EXITING)))
> > 		goto out_unlock;
> > 	iocb->ki_notify.target = target;
> > 
> > 	if (iocb->ki_notify.notify == (SIGEV_SIGNAL|SIGEV_THREAD_ID)) {
> > 		/*
> > 		 * This reference will be dropped when we're done with
> > 		 * the request.
> > 		 */
> > 		get_task_struct(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.
> > 	 */
> > 	iocb->ki_sigq = sigqueue_alloc();
> > 	if (unlikely(!iocb->ki_sigq)) {
> > 		put_task_struct(target);
> > 		return -EAGAIN;
> > 	}
> > 
> > 	return 0;
> >  out_unlock:
> > 	read_unlock(&tasklist_lock);
> > 	return -EINVAL;
> > }

  Thanks,

  Sébastien.

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