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Date:	Wed, 4 Jul 2012 17:38:49 +0400
From:	Alexander Smirnov <alex.bluesman.smirnov@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	davem@...emloft.net, netdev@...r.kernel.org, dbaryshkov@...il.com
Subject: Re: [PATCH net-next 1/2] ieee802154: sparse warnings: make symbols static

Hi Eric,

just a several questions:

>> >
>> > static DEFINE_SPINLOCK(flist_lock);
>>
>>
>> and of course commit 768f7c7c121e80f4 (6lowpan: add missing
>> spin_lock_init() ) must be reverted.

Do I need to create 2 separate patches: one for revert and second to
initialize spinlock correctly, or I can combine these changes in one
patch?

>
> You should validate this code with LOCKDEP

Nothing was shown by LOCKDEP for 6lowpan. :-(

I've selected the following options:

-*- Spinlock and rw-lock debugging: basic checks
-*- Mutex debugging: basic checks
-*- Lock debugging: detect incorrect freeing of live locks
[*] Lock usage statistics
[*] Lock dependency engine debugging

>
> lowpan_dellink() does a spin_lock(&flist_lock);
> while same lock can be taken by lowpan_fragment_timer_expired() from
> timer irq, -> deadlock.

What would be the best way to solve this context mismatch? Can I do
something like following:
1. create some 6lowpan internal workqueue
2. replace lowpan_fragment_timer_expired() body by queue_work() with
current list_deleting routine
3. when 6lowpan is going to be deleted - I'll flush the queue and
remove all the timers and respective fragments

Alex
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