Return-Path: Message-ID: <1413211468.2705.104.camel@jrissane-mobl.ger.corp.intel.com> Subject: Re: [PATCH v6 bluetooth-next] 6lowpan: Use skb_cow in IPHC decompression. From: Jukka Rissanen To: Martin Townsend Cc: Martin Townsend , linux-bluetooth@vger.kernel.org, linux-wpan@vger.kernel.org, marcel@holtmann.org, alex.aring@gmail.com Date: Mon, 13 Oct 2014 17:44:28 +0300 In-Reply-To: <543BCF44.1030001@xsilon.com> References: <1413194456-26351-1-git-send-email-martin.townsend@xsilon.com> <1413194456-26351-2-git-send-email-martin.townsend@xsilon.com> <1413200959.2705.90.camel@jrissane-mobl.ger.corp.intel.com> <543BCF44.1030001@xsilon.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Sender: linux-wpan-owner@vger.kernel.org List-ID: Hi Martin, and thanks for your analysis. On ma, 2014-10-13 at 14:10 +0100, Martin Townsend wrote: > Hi Jukka, > > I think there's a lock checking option in the kernel hacking configuration menu. Might be worth trying this to get more info. > I had a quick look through the code and there maybe a potential locking problem in l2cap_le_credits > it calls l2cap_get_chan_by_dcid which locks the channel lock (chan->lock) which is one of the locks in the deadlock below. If credits > max_credits in l2cap_le_credits it returns 0 but no unlock. Now l2cap_send_disconn_req may do this, I tried searching through but it called a state_change op so I gave up. > http://lxr.free-electrons.com/source/net/bluetooth/l2cap_core.c#L5539 > > You could try sticking a l2cap_chan_unlock(chan); in to see if the problem goes away. > I managed to trigger the locking issue (by running ssh over bt 6lowpan) even without your patch. So I am acking the v6 of this patch. I try to dig the root cause to that deadlock issue I am seeing. Signed-off-by: Jukka Rissanen Cheers, Jukka