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Date: Fri, 1 Apr 2016 04:01:34 +0200 From: Hannes Frederic Sowa <hannes@...essinduktion.org> To: Eric Dumazet <eric.dumazet@...il.com> Cc: davem@...emloft.net, netdev@...r.kernel.org, sasha.levin@...cle.com, daniel@...earbox.net, alexei.starovoitov@...il.com, mkubecek@...e.cz Subject: Re: [PATCH net 4/4] tcp: various missing rcu_read_lock around __sk_dst_get On 01.04.2016 03:45, Eric Dumazet wrote: > On Thu, 2016-03-31 at 18:39 -0700, Eric Dumazet wrote: >> On Fri, 2016-04-01 at 03:36 +0200, Hannes Frederic Sowa wrote: >>> On Fri, Apr 1, 2016, at 03:19, Eric Dumazet wrote: >>>> Thanks. >>>> >>>> As you can see, release_sock() messes badly lockdep (once your other >>>> patches are in ) >>>> >>>> Once we properly fix release_sock() and/or __release_sock(), all these >>>> false positives disappear. >>> >>> This was a loopback connection. I need to study release_sock and >>> __release_sock more as I cannot currently see an issue with the lockdep >>> handling. >> >> Okay, please try : >> >> diff --git a/net/core/sock.c b/net/core/sock.c >> index b67b9aedb230..570dcd91d64e 100644 >> --- a/net/core/sock.c >> +++ b/net/core/sock.c >> @@ -2429,10 +2429,6 @@ EXPORT_SYMBOL(lock_sock_nested); >> >> void release_sock(struct sock *sk) >> { >> - /* >> - * The sk_lock has mutex_unlock() semantics: >> - */ >> - mutex_release(&sk->sk_lock.dep_map, 1, _RET_IP_); >> >> spin_lock_bh(&sk->sk_lock.slock); >> if (sk->sk_backlog.tail) >> @@ -2445,6 +2441,10 @@ void release_sock(struct sock *sk) >> sk->sk_prot->release_cb(sk); >> >> sock_release_ownership(sk); >> + /* >> + * The sk_lock has mutex_unlock() semantics: >> + */ >> + mutex_release(&sk->sk_lock.dep_map, 1, _RET_IP_); >> if (waitqueue_active(&sk->sk_lock.wq)) >> wake_up(&sk->sk_lock.wq); >> spin_unlock_bh(&sk->sk_lock.slock); > > Also take a look at commit c3f9b01849ef3bc69024990092b9f42e20df7797 > > We might need to include the mutex_release() in sock_release_ownership() I thought so first, as well. But given the double check for the spin_lock and the "mutex" we end up with the same result for the lockdep_sock_is_held check. Do you see other consequences? Thanks, Hannes
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