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Subject: Re: [PATCH v2 5/8] Bluetooth: 6LoWPAN: Use connected oriented channel instead of fixed one
From: Marcel Holtmann <marcel@holtmann.org>
In-Reply-To: <1702130.YSG8MgCIJi@athlon>
Date: Mon, 26 May 2014 21:55:00 +0200
Cc: Jukka Rissanen <jukka.rissanen@linux.intel.com>,
	linux-bluetooth@vger.kernel.org
Message-Id: <33C8228A-35E1-43E7-A164-5B9E7C14FE2C@holtmann.org>
References: <1400837248-12179-1-git-send-email-jukka.rissanen@linux.intel.com> <1401107914.2400.21.camel@jrissane-mobl.ger.corp.intel.com> <DED0C0AE-2C66-4B7F-8496-A6CD1DA0230A@holtmann.org> <1702130.YSG8MgCIJi@athlon>
To: Szymon Janc <szymon.janc@gmail.com>
Sender: linux-bluetooth-owner@vger.kernel.org
List-ID: <linux-bluetooth.vger.kernel.org>

Hi Szymon,

>>>>> +static struct sk_buff *bt_6lowpan_chan_alloc_skb_cb(struct l2cap_chan
>>>>> *chan, +						    unsigned long len, int nb)
>>>>> +{
>>>>> +	return bt_skb_alloc(len, GFP_ATOMIC);
>>>> 
>>>> Does this have to be GFP_ATOMIC?
>>> 
>>> Yep, I see "BUG: sleeping function called from invalid context..."
>>> without it.
>> 
>> should we fix the caller? I am curious why this is possible in the first
>> place. The whole Bluetooth subsystem should run in a workqueue these days.
>> Do we have by any chance the wrong lock hold at this point or why is this
>> happening.
>> 
>> If we really need to keep GFP_ATOMIC here then you need to add a comment on
>> why that is. Because otherwise we will forget about it next time around.
> 
> FWIW this is due to holding hci_dev_list_lock which is RW_LOCK. For similar 
> reason there is GFP_ATOMIC in read_index_list() in mgmt.c.

okay then, any reason this can not be turned into a mutex?

Regards

Marcel