netdev - Re: [PATCH net-next 3/5] tipc: Optimizations to bearer enabling logic

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Message-ID: <20101018105017.GA16326@hmsreliant.think-freely.org>
Date:	Mon, 18 Oct 2010 06:50:17 -0400
From:	Neil Horman <nhorman@...driver.com>
To:	Paul Gortmaker <paul.gortmaker@...driver.com>
Cc:	davem@...emloft.net, netdev@...r.kernel.org,
	allan.stephens@...driver.com
Subject: Re: [PATCH net-next 3/5] tipc: Optimizations to bearer enabling logic

On Fri, Oct 15, 2010 at 05:31:16PM -0400, Paul Gortmaker wrote:
> On 10-10-15 07:00 AM, Neil Horman wrote:
> 
> [...]
> 
> > This definately looks more concise, but I don't see why its necessecary to drop
> > the tipc_net_lock around the call to enable_bearer.  The only caler of
> > tipc_register_media sets the enable_bearer pointer to the enable_bearer
> > function, and  I' don't see any path through that function which would
> > potentially retake that lock.  In fact it seems dropping it might be dangerous,
> > if other paths (like from cfg_named_msg_event), tried to enable a bearer in
> > parallel with a user space directive from the netlink socket).  With out the
> > protection of tipc_net_lock, you could use the same eth_bearer twice, and
> > corrupt that array.
> 
> I think it would be protected by config_lock. but in the end if it is
> just an academic optimization that really isn't in a hot code path
> anyway, and if it just adds more confusion than real world value, then
> I'm fine with just dropping this on the floor (and deleting the extra
> memset in a cleanup patch) -- it won't be the 1st time doing this with
> these carry forward patches, and I'm sure it won't be the last.
> 

Copy that.


> 
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