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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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