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    SubjectRe: [PATCH -mm 3/4][AIO] - AIO completion signal notification
    On Tue, 21 Nov 2006 17:02:28 -0800
    Andrew Morton <akpm@osdl.org> wrote:

    > On Mon, 20 Nov 2006 15:22:52 +0100
    > S__bastien Dugu__ <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;
    > > +
    > > +
    > > +
    > > + if (notify->notify == (SIGEV_SIGNAL|SIGEV_THREAD_ID)) {
    > > + /*
    > > + * This reference will be dropped in really_put_req() when
    > > + * we're done with the request.
    > > + */
    > > + get_task_struct(target);
    > > + }
    >
    > It worries me that this function can save away a task_struct* without
    > having taken a reference against it.
    >

    OK. Does moving 'notify->target = target;' after the get_task_struct() will
    do, or am I missing something more subtle?

    Thanks,

    Sébastien.
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