netdev - Re: [PATCH] GENETLINK: Global lock refined to family granularity

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Date:	Mon, 31 Mar 2008 18:14:40 +0200
From:	Richard MUSIL <richard.musil@...com>
To:	Thomas Graf <tgraf@...g.ch>
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH] GENETLINK: Global lock refined to family granularity

On 31.3.2008 14:26, Thomas Graf wrote:
> * Richard MUSIL <richard.musil@...com> 2008-03-31 13:21
>> It takes two locks, instead of one. I do not see, how it could be less
>> (in terms of synchronization primitives - but not necessarily mutexes)
>> if I want that level of granularity. Might be more efficient with RCU
>> lists (but I do not know), but complexity remains the same.
> 
> The synchronization mutex in genl_recv() remains and you add an
> additional global mutex genl_fam_lock and a per family lock. That's
> 2 vs 6 lock operations. It is possible to use RCU to manage the

Shame on me, I should know better (what my patch is doing). You are
right, the global lock in genl_recv remains. I guess my further
arguments are now irrelevant.
Concerning the RCU lists, I am also for better solution, the problem is,
I have never used them before, so the probability I will do it right, is
far small - but I may give it try.

<skipped the most since it is no longer relevant>

> I'm not against the idea, I just feel that the gains in your patch in
> its current form do not justify the additional locking and complextity
> costs. Combined with parallel processing and RCU lists it would be a
> no brainer and probably merged instantly.

Ok, I will see, what I can do.

Richard
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