Device that bound to XDP socket will not have zero refcount until the
userspace application will not close it. This leads to hang inside
'netdev_wait_allrefs()' if device unregistering requested:
# ip link del p1
< hang on recvmsg on netlink socket >
# ps -x | grep ip
5126 pts/0 D+ 0:00 ip link del p1
# journalctl -b
Jun 05 07:19:16 kernel:
unregister_netdevice: waiting for p1 to become free. Usage count = 1
Jun 05 07:19:27 kernel:
unregister_netdevice: waiting for p1 to become free. Usage count = 1
...
Fix that by implementing NETDEV_UNREGISTER event notification handler
to properly clean up all the resources and unref device.
This should also allow socket killing via ss(8) utility.
Fixes: 965a99098443 ("xsk: add support for bind for Rx")
Signed-off-by: Ilya Maximets <[email protected]>
---
net/xdp/xsk.c | 62 ++++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 61 insertions(+), 1 deletion(-)
diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index a14e8864e4fa..3f3979579d21 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -693,6 +693,54 @@ static int xsk_mmap(struct file *file, struct socket *sock,
size, vma->vm_page_prot);
}
+static int xsk_notifier(struct notifier_block *this,
+ unsigned long msg, void *ptr)
+{
+ struct sock *sk;
+ struct net_device *dev = netdev_notifier_info_to_dev(ptr);
+ struct net *net = dev_net(dev);
+ int i, unregister_count = 0;
+
+ mutex_lock(&net->xdp.lock);
+ sk_for_each(sk, &net->xdp.list) {
+ struct xdp_sock *xs = xdp_sk(sk);
+
+ mutex_lock(&xs->mutex);
+ switch (msg) {
+ case NETDEV_UNREGISTER:
+ if (dev != xs->dev)
+ break;
+
+ sk->sk_err = ENETDOWN;
+ if (!sock_flag(sk, SOCK_DEAD))
+ sk->sk_error_report(sk);
+
+ /* Wait for driver to stop using the xdp socket. */
+ xdp_del_sk_umem(xs->umem, xs);
+ xs->dev = NULL;
+ synchronize_net();
+
+ /* Clear device references in umem. */
+ xdp_put_umem(xs->umem);
+ xs->umem = NULL;
+
+ unregister_count++;
+ break;
+ }
+ mutex_unlock(&xs->mutex);
+ }
+ mutex_unlock(&net->xdp.lock);
+
+ if (unregister_count) {
+ /* Wait for umem clearing completion. */
+ synchronize_net();
+ for (i = 0; i < unregister_count; i++)
+ dev_put(dev);
+ }
+
+ return NOTIFY_DONE;
+}
+
static struct proto xsk_proto = {
.name = "XDP",
.owner = THIS_MODULE,
@@ -727,7 +775,8 @@ static void xsk_destruct(struct sock *sk)
if (!sock_flag(sk, SOCK_DEAD))
return;
- xdp_put_umem(xs->umem);
+ if (xs->umem)
+ xdp_put_umem(xs->umem);
sk_refcnt_debug_dec(sk);
}
@@ -784,6 +833,10 @@ static const struct net_proto_family xsk_family_ops = {
.owner = THIS_MODULE,
};
+static struct notifier_block xsk_netdev_notifier = {
+ .notifier_call = xsk_notifier,
+};
+
static int __net_init xsk_net_init(struct net *net)
{
mutex_init(&net->xdp.lock);
@@ -816,8 +869,15 @@ static int __init xsk_init(void)
err = register_pernet_subsys(&xsk_net_ops);
if (err)
goto out_sk;
+
+ err = register_netdevice_notifier(&xsk_netdev_notifier);
+ if (err)
+ goto out_pernet;
+
return 0;
+out_pernet:
+ unregister_pernet_subsys(&xsk_net_ops);
out_sk:
sock_unregister(PF_XDP);
out_proto:
--
2.17.1
On Fri, 7 Jun 2019 20:31:43 +0300, Ilya Maximets wrote:
> +static int xsk_notifier(struct notifier_block *this,
> + unsigned long msg, void *ptr)
> +{
> + struct sock *sk;
> + struct net_device *dev = netdev_notifier_info_to_dev(ptr);
> + struct net *net = dev_net(dev);
> + int i, unregister_count = 0;
Please order the var declaration lines longest to shortest.
(reverse christmas tree)
> + mutex_lock(&net->xdp.lock);
> + sk_for_each(sk, &net->xdp.list) {
> + struct xdp_sock *xs = xdp_sk(sk);
> +
> + mutex_lock(&xs->mutex);
> + switch (msg) {
> + case NETDEV_UNREGISTER:
You should probably check the msg type earlier and not take all the
locks and iterate for other types..
On 08.06.2019 2:31, Jakub Kicinski wrote:
> On Fri, 7 Jun 2019 20:31:43 +0300, Ilya Maximets wrote:
>> +static int xsk_notifier(struct notifier_block *this,
>> + unsigned long msg, void *ptr)
>> +{
>> + struct sock *sk;
>> + struct net_device *dev = netdev_notifier_info_to_dev(ptr);
>> + struct net *net = dev_net(dev);
>> + int i, unregister_count = 0;
>
> Please order the var declaration lines longest to shortest.
> (reverse christmas tree)
Hi.
I'm not a fan of mixing 'struct's with bare types in the declarations.
Moving the 'sk' to the third place will make a hole like this:
struct net_device *dev = netdev_notifier_info_to_dev(ptr);
struct net *net = dev_net(dev);
struct sock *sk;
int i, unregister_count = 0;
Which is not looking good.
Moving to the 4th place:
struct net_device *dev = netdev_notifier_info_to_dev(ptr);
struct net *net = dev_net(dev);
int i, unregister_count = 0;
struct sock *sk;
This variant doesn't look good for me because of mixing 'struct's with
bare integers.
Do you think I need to use one of above variants?
>
>> + mutex_lock(&net->xdp.lock);
>> + sk_for_each(sk, &net->xdp.list) {
>> + struct xdp_sock *xs = xdp_sk(sk);
>> +
>> + mutex_lock(&xs->mutex);
>> + switch (msg) {
>> + case NETDEV_UNREGISTER:
>
> You should probably check the msg type earlier and not take all the
> locks and iterate for other types..
Yeah. I thought about it too. Will fix in the next version.
Best regards, Ilya Maximets.
On 10.06.2019 11:05, Ilya Maximets wrote:
> On 08.06.2019 2:31, Jakub Kicinski wrote:
>> On Fri, 7 Jun 2019 20:31:43 +0300, Ilya Maximets wrote:
>>> +static int xsk_notifier(struct notifier_block *this,
>>> + unsigned long msg, void *ptr)
>>> +{
>>> + struct sock *sk;
>>> + struct net_device *dev = netdev_notifier_info_to_dev(ptr);
>>> + struct net *net = dev_net(dev);
>>> + int i, unregister_count = 0;
>>
>> Please order the var declaration lines longest to shortest.
>> (reverse christmas tree)
>
> Hi.
> I'm not a fan of mixing 'struct's with bare types in the declarations.
> Moving the 'sk' to the third place will make a hole like this:
>
> struct net_device *dev = netdev_notifier_info_to_dev(ptr);
> struct net *net = dev_net(dev);
> struct sock *sk;
> int i, unregister_count = 0;
>
> Which is not looking good.
> Moving to the 4th place:
>
> struct net_device *dev = netdev_notifier_info_to_dev(ptr);
> struct net *net = dev_net(dev);
> int i, unregister_count = 0;
> struct sock *sk;
I've sent v3 with this variant and with moved msg check to the top level.
>
> This variant doesn't look good for me because of mixing 'struct's with
> bare integers.
>
> Do you think I need to use one of above variants?
>
>>
>>> + mutex_lock(&net->xdp.lock);
>>> + sk_for_each(sk, &net->xdp.list) {
>>> + struct xdp_sock *xs = xdp_sk(sk);
>>> +
>>> + mutex_lock(&xs->mutex);
>>> + switch (msg) {
>>> + case NETDEV_UNREGISTER:
>>
>> You should probably check the msg type earlier and not take all the
>> locks and iterate for other types..
>
> Yeah. I thought about it too. Will fix in the next version.
>
> Best regards, Ilya Maximets.
>