On Fri, Nov 18, 2022 at 07:19:09PM +0000, Joel Fernandes (Google) wrote:
> From: Eric Dumazet <edumazet@xxxxxxxxxx>
>
> Currently, the inetdev_destroy() function waits for an RCU grace period
> before decrementing the refcount and freeing memory. This causes a delay
> with a new RCU configuration that tries to save power, which results in the
> network interface disappearing later than expected. The resulting delay
> causes test failures on ChromeOS.
>
> Refactor the code such that the refcount is freed before the grace period
> and memory is freed after. With this a ChromeOS network test passes that
> does 'ip netns del' and polls for an interface disappearing, now passes.
>
> Reported-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx>
> Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
> Signed-off-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx>
Queued and pushed, thank you both!
This patch can go as-is based on Eric's Signed-off-by, but the first
one of course needs at least an ack.
Thanx, Paul
> ---
> net/ipv4/devinet.c | 19 ++++++++++---------
> 1 file changed, 10 insertions(+), 9 deletions(-)
>
> diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
> index e8b9a9202fec..b0acf6e19aed 100644
> --- a/net/ipv4/devinet.c
> +++ b/net/ipv4/devinet.c
> @@ -234,13 +234,20 @@ static void inet_free_ifa(struct in_ifaddr *ifa)
> call_rcu(&ifa->rcu_head, inet_rcu_free_ifa);
> }
>
> +static void in_dev_free_rcu(struct rcu_head *head)
> +{
> + struct in_device *idev = container_of(head, struct in_device, rcu_head);
> +
> + kfree(rcu_dereference_protected(idev->mc_hash, 1));
> + kfree(idev);
> +}
> +
> void in_dev_finish_destroy(struct in_device *idev)
> {
> struct net_device *dev = idev->dev;
>
> WARN_ON(idev->ifa_list);
> WARN_ON(idev->mc_list);
> - kfree(rcu_dereference_protected(idev->mc_hash, 1));
> #ifdef NET_REFCNT_DEBUG
> pr_debug("%s: %p=%s\n", __func__, idev, dev ? dev->name : "NIL");
> #endif
> @@ -248,7 +255,7 @@ void in_dev_finish_destroy(struct in_device *idev)
> if (!idev->dead)
> pr_err("Freeing alive in_device %p\n", idev);
> else
> - kfree(idev);
> + call_rcu(&idev->rcu_head, in_dev_free_rcu);
> }
> EXPORT_SYMBOL(in_dev_finish_destroy);
>
> @@ -298,12 +305,6 @@ static struct in_device *inetdev_init(struct net_device *dev)
> goto out;
> }
>
> -static void in_dev_rcu_put(struct rcu_head *head)
> -{
> - struct in_device *idev = container_of(head, struct in_device, rcu_head);
> - in_dev_put(idev);
> -}
> -
> static void inetdev_destroy(struct in_device *in_dev)
> {
> struct net_device *dev;
> @@ -328,7 +329,7 @@ static void inetdev_destroy(struct in_device *in_dev)
> neigh_parms_release(&arp_tbl, in_dev->arp_parms);
> arp_ifdown(dev);
>
> - call_rcu(&in_dev->rcu_head, in_dev_rcu_put);
> + in_dev_put(in_dev);
> }
>
> int inet_addr_onlink(struct in_device *in_dev, __be32 a, __be32 b)
> --
> 2.38.1.584.g0f3c55d4c2-goog
>
