On Fri, Apr 17, 2009 at 08:09:23AM +0800, Herbert Xu wrote:
> On Thu, Apr 16, 2009 at 10:57:45PM +0300, Michael S. Tsirkin wrote:
> >
> > This last bit seems to make a simple test using a non-persistent tap device
> > deadlock for me: we don't drop a reference acquired with __tun_get sock
> > unregister_netdevice blocks printing unregister_netdevice: waiting for tap0 to
> > become free. Usage count = 1.
>
> Ah yes, I'd overlooked the fact that the original code didn't
> require the tfile refcount to hit zero. Now we do. Here's an
> updated version of the first patch. The second patch should still
> work as is.
>
> tun: Only free a netdev when all tun descriptors are closed
...
> @@ -1275,20 +1278,17 @@ static int tun_chr_close(struct inode *inode, struct file *file)
> struct tun_file *tfile = file->private_data;
> struct tun_struct *tun = __tun_get(tfile);
>
> -
> if (tun) {
> - DBG(KERN_INFO "%s: tun_chr_close\n", tun->dev->name);
> -
> - rtnl_lock();
> - __tun_detach(tun);
> -
> /* If desireable, unregister the netdevice. */
> - if (!(tun->flags & TUN_PERSIST)) {
> - sock_put(tun->sk);
> - unregister_netdevice(tun->dev);
> - }
> + if (!(tun->flags & TUN_PERSIST))
> + unregister_netdev(tun->dev);
> + tun_put(tun);
> + } else
> + tun = tfile->tun;
>
> - rtnl_unlock();
> + if (tun) {
> + DBG(KERN_INFO "%s: tun_chr_close\n", tun->dev->name);
> + sock_put(tun->sk);
> }
>
> put_net(tfile->net);
Does this work with TUN_PERSIST off?
I haven't tested this, but won't unregister_netdev block forever
waiting for device reference to become 0? Maybe you want
+ tun_put(tun);
+ if (!(tun->flags & TUN_PERSIST))
+ unregister_netdev(tun->dev);
or is there a race here?
--
MST
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