RE: Locking down a socket, milestone 1

On 24-Apr-2002 Seigo Tanimura wrote:
> I am now working on locking down a socket.  (I have heard that Jeffrey
> Hsu is also doing that, but I have never seen his patch.  Has anyone
> seen that?) My first milestone patch is now available at:
> 
> 
> http://people.FreeBSD.org/~tanimura/patches/socket_milestone1.diff.gz
> 
> 
> The works I have done so far are:
> 
> 
> - Determine the lock required to protect each of the members in struct
>   socket.
> 
> - Add mutexes to each of the sockbufs in a socket as BSD/OS does.
> 
> - Lock down so_count, so_options, so_linger and so_state.
> 
> - Add a global mutex socq_lock to protect the connection queues of a
>   listening socket.  Lock socq_lock to lock two sockets at once,
>   followed by enqueuing or dequeuing a socket, or moving a socket across
>   queues.  socq_lock is not an sx lock because we usually have to lock
>   two sockets to modify them.

Do you actually lock two sockets at once or do you lock one at a time while
holding socq_lock.  If you do lock two at once, what is the defined locking
order?

-- 

John Baldwin <[e-mail]>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve!"  -  http://www.FreeBSD.org/

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