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SubjectRe: __pm_runtime_resume() returns -1 Was: Regression in 2.6.36
On Fri, 22 Oct 2010 15:38:01 +0200
Christian Bahls <lkml@qb352.de> wrote:

> Thanks to the help by Matthias Schniedermeyer
> i was able to bisect the change in less than 24 hours
>
> The regression seems to have been introduced by the merge:
> 92b4522f72916ff2675060e29e4b24cf26ab59ce
>
> Parent: 67a3e12b05e055c0415c556a315a3d3eb637e29e (Linux 2.6.35-rc1)
> Parent: 2903037400a26e7c0cc93ab75a7d62abfacdf485 (net: fix
> sk_forward_alloc corruptions)
> Branches: compile, remotes/origin/master, work
> Follows: v2.6.35-rc1
> Precedes: v2.6.36-rc1
>
> Merge branch 'master' of
> master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6
>
> Which (according to git bisect visualize) contains following Change:
>
> Author: Eric Dumazet <eric.dumazet@gmail.com> 2010-05-29 09:20:48
> Committer: David S. Miller <davem@davemloft.net> 2010-05-29 09:20:48
> Child: 92b4522f72916ff2675060e29e4b24cf26ab59ce (Merge branch
> 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6)
> Branches: compile, master, remotes/origin/master, remotes/v35/master, work
> Follows: v2.6.34
> Precedes: first_bad, v2.6.35-rc2
>
> net: fix sk_forward_alloc corruptions
>
> As David found out, sock_queue_err_skb() should be called with socket
> lock hold, or we risk sk_forward_alloc corruption, since we use non
> atomic operations to update this field.
>
> This patch adds bh_lock_sock()/bh_unlock_sock() pair to three spots.
> (BH already disabled)
>
> 1) skb_tstamp_tx()
> 2) Before calling ip_icmp_error(), in __udp4_lib_err()
> 3) Before calling ipv6_icmp_error(), in __udp6_lib_err()

I suspect your bisection went wrong :(

>
> ------------------------------ net/core/skbuff.c ------------------------------
> index 4667d4d..f2913ae 100644
> @@ -2992,7 +2992,11 @@ void skb_tstamp_tx(struct sk_buff *orig_skb,
> memset(serr, 0, sizeof(*serr));
> serr->ee.ee_errno = ENOMSG;
> serr->ee.ee_origin = SO_EE_ORIGIN_TIMESTAMPING;
> +
> + bh_lock_sock(sk);
> err = sock_queue_err_skb(sk, skb);
> + bh_unlock_sock(sk);
> +
> if (err)
> kfree_skb(skb);
> }
>
> -------------------------------- net/ipv4/udp.c --------------------------------
> index b9d0d40..acdc9be 100644
> @@ -634,7 +634,9 @@ void __udp4_lib_err(struct sk_buff *skb, u32 info,
> struct udp_table *udptable)
> if (!harderr || sk->sk_state != TCP_ESTABLISHED)
> goto out;
> } else {
> + bh_lock_sock(sk);
> ip_icmp_error(sk, skb, err, uh->dest, info, (u8 *)(uh+1));
> + bh_unlock_sock(sk);
> }
> sk->sk_err = err;
> sk->sk_error_report(sk);
>
> -------------------------------- net/ipv6/udp.c --------------------------------
> index 87be586..3048f90 100644
> @@ -466,9 +466,11 @@ void __udp6_lib_err(struct sk_buff *skb, struct
> inet6_skb_parm *opt,
> if (sk->sk_state != TCP_ESTABLISHED && !np->recverr)
> goto out;
>
> - if (np->recverr)
> + if (np->recverr) {
> + bh_lock_sock(sk);
> ipv6_icmp_error(sk, skb, err, uh->dest, ntohl(info), (u8 *)(uh+1));
> -
> + bh_unlock_sock(sk);
> + }
> sk->sk_err = err;
> sk->sk_error_report(sk);
> out:

It's really hard to see how that change could break the resume
operation.



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