From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Miller <davem@davemloft.net>
Subject: Re: Weird locking in __release_sock()?
Date: Wed, 22 Jun 2011 16:42:14 -0700 (PDT)
Message-ID: <20110622.164214.415427796273622733.davem@davemloft.net>
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From: David Daney <ddaney@caviumnetworks.com>
Date: Wed, 22 Jun 2011 16:31:13 -0700

> In the case of an IPv4 TCP socket, sk_backlog_rcv() calls
> tcp_v4_do_rcv(), which is documented like this:
> 
> /* The socket must have it's spinlock held when we get
>  * here.
> .
> .
> .
> */
> 
> Q: How can this be correct?

sk->lock.owned will be "1" while the backlog is processed.

Exclusive access to the socket is indicated by one of the
following two conditions being true:

1) sk->lock.slock being held
2) sk->lock.owned being non-zero