netdev - Re: [IPV4 3/5] fib_trie: dump doesnt use RCU

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Message-ID: <4798348B.4080300@trash.net>
Date:	Thu, 24 Jan 2008 07:47:39 +0100
From:	Patrick McHardy <kaber@...sh.net>
To:	David Miller <davem@...emloft.net>
CC:	shemminger@...ux-foundation.org, netdev@...r.kernel.org
Subject: Re: [IPV4 3/5] fib_trie: dump doesnt use RCU

David Miller wrote:
> From: Patrick McHardy <kaber@...sh.net>
> Date: Thu, 24 Jan 2008 07:41:08 +0100
>
>   
>> David Miller wrote:
>>     
>>> and nothing in that code path retakes the RTNL semaphore.
>>>       
>> Actually we're always holding the rtnl during dumps, nlk->cb_mutex points
>> to rtnl_mutex in case of rtnetlink. It used to be held only during the first
>> ->dump invocation and not on continuations, but I changed this a few 
>> versions ago.
>>     
>
> My bad.  Thanks for the correction Patrick.
>
> But continuations can occur on subsequent recvmsg() calls,
> does it return to userspace with the mutex held?  If so
> I'm pretty sure that's not allowed.
>   

No, the mutex is dropped between different ->dump invocations.

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