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* [PATCH net v2] tun: wake up waitqueues after IFF_UP is set
@ 2019-06-17 13:26 Fei Li
  2019-06-18 17:55 ` David Miller
  0 siblings, 1 reply; 3+ messages in thread
From: Fei Li @ 2019-06-17 13:26 UTC (permalink / raw)
  To: davem, jasowang, netdev, linux-kernel; +Cc: zhengfeiran, duanxiongchun, Fei Li

Currently after setting tap0 link up, the tun code wakes tx/rx waited
queues up in tun_net_open() when .ndo_open() is called, however the
IFF_UP flag has not been set yet. If there's already a wait queue, it
would fail to transmit when checking the IFF_UP flag in tun_sendmsg().
Then the saving vhost_poll_start() will add the wq into wqh until it
is waken up again. Although this works when IFF_UP flag has been set
when tun_chr_poll detects; this is not true if IFF_UP flag has not
been set at that time. Sadly the latter case is a fatal error, as
the wq will never be waken up in future unless later manually
setting link up on purpose.

Fix this by moving the wakeup process into the NETDEV_UP event
notifying process, this makes sure IFF_UP has been set before all
waited queues been waken up.

Signed-off-by: Fei Li <lifei.shirley@bytedance.com>
Acked-by: Jason Wang <jasowang@redhat.com>
---
 drivers/net/tun.c | 19 +++++++++----------
 1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index c452d6d831dd..d7c55e0fa8f4 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1014,18 +1014,8 @@ static void tun_net_uninit(struct net_device *dev)
 /* Net device open. */
 static int tun_net_open(struct net_device *dev)
 {
-	struct tun_struct *tun = netdev_priv(dev);
-	int i;
-
 	netif_tx_start_all_queues(dev);
 
-	for (i = 0; i < tun->numqueues; i++) {
-		struct tun_file *tfile;
-
-		tfile = rtnl_dereference(tun->tfiles[i]);
-		tfile->socket.sk->sk_write_space(tfile->socket.sk);
-	}
-
 	return 0;
 }
 
@@ -3634,6 +3624,7 @@ static int tun_device_event(struct notifier_block *unused,
 {
 	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
 	struct tun_struct *tun = netdev_priv(dev);
+	int i;
 
 	if (dev->rtnl_link_ops != &tun_link_ops)
 		return NOTIFY_DONE;
@@ -3643,6 +3634,14 @@ static int tun_device_event(struct notifier_block *unused,
 		if (tun_queue_resize(tun))
 			return NOTIFY_BAD;
 		break;
+	case NETDEV_UP:
+		for (i = 0; i < tun->numqueues; i++) {
+			struct tun_file *tfile;
+
+			tfile = rtnl_dereference(tun->tfiles[i]);
+			tfile->socket.sk->sk_write_space(tfile->socket.sk);
+		}
+		break;
 	default:
 		break;
 	}
-- 
2.11.0


^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH net v2] tun: wake up waitqueues after IFF_UP is set
  2019-06-17 13:26 [PATCH net v2] tun: wake up waitqueues after IFF_UP is set Fei Li
@ 2019-06-18 17:55 ` David Miller
  2019-06-19 16:02   ` [External Email] " 李菲
  0 siblings, 1 reply; 3+ messages in thread
From: David Miller @ 2019-06-18 17:55 UTC (permalink / raw)
  To: lifei.shirley; +Cc: jasowang, netdev, linux-kernel, zhengfeiran, duanxiongchun

From: Fei Li <lifei.shirley@bytedance.com>
Date: Mon, 17 Jun 2019 21:26:36 +0800

> Currently after setting tap0 link up, the tun code wakes tx/rx waited
> queues up in tun_net_open() when .ndo_open() is called, however the
> IFF_UP flag has not been set yet. If there's already a wait queue, it
> would fail to transmit when checking the IFF_UP flag in tun_sendmsg().
> Then the saving vhost_poll_start() will add the wq into wqh until it
> is waken up again. Although this works when IFF_UP flag has been set
> when tun_chr_poll detects; this is not true if IFF_UP flag has not
> been set at that time. Sadly the latter case is a fatal error, as
> the wq will never be waken up in future unless later manually
> setting link up on purpose.
> 
> Fix this by moving the wakeup process into the NETDEV_UP event
> notifying process, this makes sure IFF_UP has been set before all
> waited queues been waken up.
> 
> Signed-off-by: Fei Li <lifei.shirley@bytedance.com>
> Acked-by: Jason Wang <jasowang@redhat.com>

Applied and queued up for -stable, thanks.

^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [External Email] Re: [PATCH net v2] tun: wake up waitqueues after IFF_UP is set
  2019-06-18 17:55 ` David Miller
@ 2019-06-19 16:02   ` " 李菲
  0 siblings, 0 replies; 3+ messages in thread
From: 李菲 @ 2019-06-19 16:02 UTC (permalink / raw)
  To: David Miller; +Cc: Jason Wang, netdev, linux-kernel, zhengfeiran, duanxiongchun

Thanks.

Have a nice day
Fei

On Wed, Jun 19, 2019 at 1:55 AM David Miller <davem@davemloft.net> wrote:
>
> From: Fei Li <lifei.shirley@bytedance.com>
> Date: Mon, 17 Jun 2019 21:26:36 +0800
>
> > Currently after setting tap0 link up, the tun code wakes tx/rx waited
> > queues up in tun_net_open() when .ndo_open() is called, however the
> > IFF_UP flag has not been set yet. If there's already a wait queue, it
> > would fail to transmit when checking the IFF_UP flag in tun_sendmsg().
> > Then the saving vhost_poll_start() will add the wq into wqh until it
> > is waken up again. Although this works when IFF_UP flag has been set
> > when tun_chr_poll detects; this is not true if IFF_UP flag has not
> > been set at that time. Sadly the latter case is a fatal error, as
> > the wq will never be waken up in future unless later manually
> > setting link up on purpose.
> >
> > Fix this by moving the wakeup process into the NETDEV_UP event
> > notifying process, this makes sure IFF_UP has been set before all
> > waited queues been waken up.
> >
> > Signed-off-by: Fei Li <lifei.shirley@bytedance.com>
> > Acked-by: Jason Wang <jasowang@redhat.com>
>
> Applied and queued up for -stable, thanks.

^ permalink raw reply	[flat|nested] 3+ messages in thread

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Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2019-06-17 13:26 [PATCH net v2] tun: wake up waitqueues after IFF_UP is set Fei Li
2019-06-18 17:55 ` David Miller
2019-06-19 16:02   ` [External Email] " 李菲

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