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

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Date:	Wed, 21 Aug 2013 15:53:54 -0700
From:	Pravin Shelar <pshelar@...ira.com>
To:	Oliver Hartkopp <socketcan@...tkopp.net>
Cc:	Johannes Berg <johannes@...solutions.net>,
	netdev <netdev@...r.kernel.org>, Thomas Graf <tgraf@...g.ch>
Subject: Re: [PATCH 0/2] fix generic netlink locking issue(s)

This looks like more general problem and not specific to genl_ctrl
family. I have couple of fixes for issues you are seeing, I will send
out those patches soon.

On Wed, Aug 21, 2013 at 12:05 PM, Oliver Hartkopp
<socketcan@...tkopp.net> wrote:
> 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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