On Mon, Dec 5, 2016 at 8:28 AM, Herbert Xu <herb...@gondor.apana.org.au> wrote:
> On Mon, Dec 05, 2016 at 03:26:00PM +0800, Herbert Xu wrote:
>> On Mon, Dec 05, 2016 at 03:19:46PM +0800, Herbert Xu wrote:
>> >
>> > Thanks for the patch. It'll obviously work but I wanted avoid that
>> > because it penalises the common path for the rare case.
>> >
>> > Andrey, please try this patch and let me know if it's any better.
>> >
>> > ---8<---
>> > Subject: netlink: Do not schedule work from sk_destruct
>>
>> Crap, I screwed it up again. Here is a v2 which moves the atomic
>> call into the RCU callback as otherwise the socket can be freed from
>> another path while we await the RCU callback.
>
> With the move it no longer makes sense to rename deferred_put_nlk_sk
> so here is v3 which restores the original name.
>
> ---8<---
> It is wrong to schedule a work from sk_destruct using the socket
> as the memory reserve because the socket will be freed immediately
> after the return from sk_destruct.
>
> Instead we should do the deferral prior to sk_free.
>
> This patch does just that.
>
> Fixes: 707693c8a498 ("netlink: Call cb->done from a worker thread")
> Signed-off-by: Herbert Xu <herb...@gondor.apana.org.au>
>
> diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
> index 602e5eb..246f29d 100644
> --- a/net/netlink/af_netlink.c
> +++ b/net/netlink/af_netlink.c
> @@ -322,11 +322,13 @@ static void netlink_skb_set_owner_r(struct sk_buff
> *skb, struct sock *sk)
> sk_mem_charge(sk, skb->truesize);
> }
>
> -static void __netlink_sock_destruct(struct sock *sk)
> +static void netlink_sock_destruct(struct sock *sk)
> {
> struct netlink_sock *nlk = nlk_sk(sk);
>
> if (nlk->cb_running) {
> + if (nlk->cb.done)
> + nlk->cb.done(&nlk->cb);
> module_put(nlk->cb.module);
> kfree_skb(nlk->cb.skb);
> }
> @@ -348,21 +350,7 @@ static void netlink_sock_destruct_work(struct
> work_struct *work)
> struct netlink_sock *nlk = container_of(work, struct netlink_sock,
> work);
>
> - nlk->cb.done(&nlk->cb);
> - __netlink_sock_destruct(&nlk->sk);
> -}
> -
> -static void netlink_sock_destruct(struct sock *sk)
> -{
> - struct netlink_sock *nlk = nlk_sk(sk);
> -
> - if (nlk->cb_running && nlk->cb.done) {
> - INIT_WORK(&nlk->work, netlink_sock_destruct_work);
> - schedule_work(&nlk->work);
> - return;
> - }
> -
> - __netlink_sock_destruct(sk);
> + sk_free(&nlk->sk);
> }
>
> /* This lock without WQ_FLAG_EXCLUSIVE is good on UP and it is _very_ bad on
> @@ -667,8 +655,18 @@ static int netlink_create(struct net *net, struct socket
> *sock, int protocol,
> static void deferred_put_nlk_sk(struct rcu_head *head)
> {
> struct netlink_sock *nlk = container_of(head, struct netlink_sock,
> rcu);
> + struct sock *sk = &nlk->sk;
> +
> + if (!atomic_dec_and_test(&sk->sk_refcnt))
> + return;
> +
> + if (nlk->cb_running && nlk->cb.done) {
> + INIT_WORK(&nlk->work, netlink_sock_destruct_work);
> + schedule_work(&nlk->work);
> + return;
> + }
>
> - sock_put(&nlk->sk);
> + sk_free(sk);
> }
>
> static int netlink_release(struct socket *sock)
> --
> Email: Herbert Xu <herb...@gondor.apana.org.au>
> Home Page: http://gondor.apana.org.au/~herbert/
> PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
Hi Herbert,
Tested the last version of your patch, the reports go away.
Thanks for the fix!
Tested-by: Andrey Konovalov <andreyk...@google.com>
