2019-06-17 13:28:27

by 李菲

Subject: [PATCH net v2] tun: wake up waitqueues after IFF_UP is set

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 <[email protected]>
Acked-by: Jason Wang <[email protected]>
---
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

2019-06-18 17:56:26

by David Miller

Subject: Re: [PATCH net v2] tun: wake up waitqueues after IFF_UP is set

From: Fei Li <[email protected]>
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 <[email protected]>
> Acked-by: Jason Wang <[email protected]>

Applied and queued up for -stable, thanks.

2019-06-19 16:03:14

by 李菲

Subject: Re: [External Email] Re: [PATCH net v2] tun: wake up waitqueues after IFF_UP is set

Thanks.

Have a nice day
Fei

On Wed, Jun 19, 2019 at 1:55 AM David Miller <[email protected]> wrote:
>
> From: Fei Li <[email protected]>
> 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 <[email protected]>
> > Acked-by: Jason Wang <[email protected]>
>
> Applied and queued up for -stable, thanks.