netdev - Re: [PATCH 0/2] fix generic netlink locking issue(s)

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Message-ID: <52150F87.90207@hartkopp.net>
Date:	Wed, 21 Aug 2013 21:05:43 +0200
From:	Oliver Hartkopp <socketcan@...tkopp.net>
To:	Johannes Berg <johannes@...solutions.net>
CC:	netdev@...r.kernel.org, Thomas Graf <tgraf@...g.ch>
Subject: Re: [PATCH 0/2] fix generic netlink locking issue(s)

On 21.08.2013 16:08, Johannes Berg wrote:
> Here's another attempt at fixing the genetlink locking issue,
> hopefully better tested this time. Sorry about the mess the 
> previous version caused.
> 
> I really didn't find a way to "simply" add locking, no matter
> which way I turn genetlink is special because it would then use
> the same locks "inside" and "outside" the generic netlink family;
> "inside" because I'm trying to protect the otherwise unlocked
> dump call, and "outside" because it itself is a generic netlink
> family so needs to protect things there.
> 
> As a result, I've turned to RCU and (hopefully) made it safe.
> The unregistration can get fairly expensive with all the calls
> to synchronize_rcu(), but I don't see any better way, and it's
> hopefully really rare.
> 
> The only place that now uses RCU is ctrl_dumpfamily(), but it'd
> be possible to use it in other places. I didn't want to do it
> in this patch, but I also don't see any candidates where that 
> would really make sense. 
> 
> The first patch should obviously go into 3.11, I'll let you 
> decide about the second. This one might actually be easier to
> backport than the original one, but it'd still have to be done
> carefully.

I applied both patches.
The lockdep issue vanished and i still can write emails :-)

Thanks Johannes.

Tested-by: Oliver Hartkopp <socketcan@...tkopp.net>


> 
> johannes
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