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On Thu, 2006-11-09 at 19:08 +0000, Christoph Hellwig wrote:
> > +static long aio_setup_sigevent(struct kiocb *iocb,
> > + struct sigevent __user *user_event)
> > +{
> > + int error = 0;
> > + sigevent_t event;
> > + struct task_struct *target;
> > + unsigned long flags;
> > +
> > + if (!access_ok(VERIFY_READ, user_event, sizeof(struct sigevent)))
> > + return -EFAULT;
> > +
> > + if (copy_from_user(&event, user_event, sizeof (event)))
> > + return -EFAULT;> > +> > > +> > + /* Check for the SIGEV_NONE case */> > + if (event.sigev_notify == SIGEV_NONE)> > + return 0;> > +> > + /* Setup the request completion notification parameters */
> > + iocb->ki_notify.notify = event.sigev_notify;> > + iocb->ki_notify.signo = event.sigev_signo;> > + iocb->ki_notify.value = event.sigev_value;> > +> > + /* Now get the notification target */> > + read_lock(&tasklist_lock);> > +> > + if ((target = good_sigevent(&event))) {> > +> > + spin_lock_irqsave(&target->sighand->siglock, flags);
> > +> > + if (!(target->flags & PF_EXITING)) {
> > + iocb->ki_notify.target = target;
> > +
> > + spin_unlock_irqrestore(&target->sighand->siglock, flags);
> > +> > I don't think there's a need to have the siglock for checking PF_EXITING,
> and I also don't see why you need it for the assignment to
> iocb->ki_notify.target. What is it intended to protect?
Right, some remnant that managed to sneak through, will fix.
> > > + /*> > + * Get a ref on the task. It is dropped in really_put_req()
> > + * when we're done with the iocb, be it from the normal
> > + * completion path, the cancellation path or an error path.
> > + */> > + if (iocb->ki_notify.notify == (SIGEV_SIGNAL|SIGEV_THREAD_ID))
> > + get_task_struct(target);> > + } else {> > + spin_unlock_irqrestore(&target->sighand->siglock, flags);
> > + error = -EINVAL;> > + }> > + } else> > + error = -EINVAL;> > +> > + read_unlock(&tasklist_lock);> > +> > + if (!error) {> > + /*> > + * Alloc a sigqueue for this request> > + *> > + * 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.
> > + */> > + if (unlikely(!(iocb->ki_sigq = sigqueue_alloc())))
> > + error = -EAGAIN;> > We leak the task reference here.
I don't think so, the reference is dropped in really_pu_req() when
the iocb is freed, unless I missed something.
> > All in all aio_setup_sigevent is a big mess and the style is very odd.
> It's also overcommented on what's beeing done instead of why.
> I've attached an draft on how it should look like below.
> > > + /* handle setting up the sigevent for POSIX AIO signals */
> > + req->ki_notify.notify = SIGEV_NONE;> > +> > + if (iocb->aio_sigeventp) {> > + ret = aio_setup_sigevent(req,> > + (struct sigevent __user *)(unsigned long)
> > + iocb->aio_sigeventp);> > + if (ret)> > + goto out_put_req;> > + }> > +> > ret = aio_setup_iocb(req);
> >
> > if (ret)
> > @@ -1610,6 +1729,10 @@ int fastcall io_submit_one(struct kioctx
> > return 0;
> >
> > out_put_req:
> > + /* Undo the sigqueue alloc if someting went bad */
> > + if (req->ki_sigq)
> > + sigqueue_free(req->ki_sigq);
> > +> > Please put this after a separate label, so only callers after
> aio_setup_sigevent try to check ki_sigq.
Okay, cleaner that way.
> > > > 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;
> 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;
> }
>
Cool, clearly better without taking the siglock, but again I don't
think the put_task_struct() is needed here.
Thanks,
Sébastien.
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