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From: Antonio Quartulli <a@unstable.cc>
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Date: Sat, 19 Dec 2015 19:09:02 +0800
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Subject: Re: [B.A.T.M.A.N.] [PATCH-maint] batman-adv: fix lockdep splat when
 doing mcast_free
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Cc: Simon Wunderlich <simon@open-mesh.com>

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On 19/12/15 17:32, Sven Eckelmann wrote:
> On Saturday 19 December 2015 09:04:05 Linus L=FCssing wrote:
>>> From: Simon Wunderlich <simon@open-mesh.com>
>>>
>>> While testing, we got something like this:
>>>
>>> WARNING: CPU: 0 PID: 238 at net/batman-adv/multicast.c:142 batadv_mca=
st_mla_tt_retract+0x94/0x205 [batman_adv]()
>>> [...]
>>> Call Trace:
>>> [<ffffffff815fc597>] dump_stack+0x4b/0x64
>>> [<ffffffff810b34dc>] warn_slowpath_common+0xbc/0x120
>>> [<ffffffffa0024ec5>] ? batadv_mcast_mla_tt_retract+0x94/0x205 [batman=
_adv]
>>> [<ffffffff810b3705>] warn_slowpath_null+0x15/0x20
>>> [<ffffffffa0024ec5>] batadv_mcast_mla_tt_retract+0x94/0x205 [batman_a=
dv]
>>> [<ffffffffa00273fe>] batadv_mcast_free+0x36/0x39 [batman_adv]
>>> [<ffffffffa0020c77>] batadv_mesh_free+0x7d/0x13f [batman_adv]
>>> [<ffffffffa0036a6b>] batadv_softif_free+0x15/0x25 [batman_adv]
>>> [...]
>>>
>>> Signed-off-by: Simon Wunderlich <simon@open-mesh.com>
>>
>> Fixes: 5b95c427d187 ("batman-adv: Annotate deleting functions with ext=
ernal lock via lockdep")
>> Acked-by: Linus L=FCssing <linus.luessing@c0d3.blue>
>=20
> I am confused why this should fix a commit which is there to find such =
problems.

Am I wrong or also the commit message is misleading? Looks like it is
"fixing" a bogus lockdep check...but as far as I can say this patch is
making sure that the lock is held in that particular point.

If we want to "fix the lockdep" then we should remove the
lockdep_assert_held(), but I don't think this is the goal of the whole
discussion.

Cheers,

--=20
Antonio Quartulli


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