From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexander Aring Subject: Re: [PATCH net] 6lowpan: add missing fragment list spinlock Date: Wed, 5 Feb 2014 08:47:30 +0100 Message-ID: <20140205074729.GA27973@omega> References: <1391511473-30000-1-git-send-email-alex.aring@gmail.com> <20140204.203203.1380460749447396879.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-zigbee-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org To: David Miller Return-path: Content-Disposition: inline In-Reply-To: <20140204.203203.1380460749447396879.davem-fT/PcQaiUtIeIZ0/mPfg9Q@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linux-zigbee-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: netdev.vger.kernel.org Hi David, thanks for your reply. On Tue, Feb 04, 2014 at 08:32:03PM -0800, David Miller wrote: > From: Alexander Aring > Date: Tue, 4 Feb 2014 11:57:53 +0100 > > > @@ -197,7 +197,9 @@ static void lowpan_fragment_timer_expired(unsigned long entry_addr) > > > > pr_debug("timer expired for frame with tag %d\n", entry->tag); > > > > + spin_lock_bh(&flist_lock); > > list_del(&entry->list); > > + spin_unlock_bh(&flist_lock); > > dev_kfree_skb(entry->skb); > > kfree(entry); > > } > > This will deadlock, because the other code path holding flist_lock calls > del_timer_sync() to wait for this timer to return. > ok. I detected this some months ago and I talked with Werner Almesberger about that. He talked something about del_timer_sync too and other issues, but I didn't understand that I open a new deadlock case. Now I learned something new things, thanks. :-) > The synchornization in this code is really a big mess. That is one thing which I also detected so I decide to make a new implementation based on net/ipv6/reassembly.c which also used the inet_frag api. I will bring these patches mainline and I hope it will remove the most of the race condigition. But then it's only solved in net-next branch. - Alex ------------------------------------------------------------------------------ Managing the Performance of Cloud-Based Applications Take advantage of what the Cloud has to offer - Avoid Common Pitfalls. Read the Whitepaper. http://pubads.g.doubleclick.net/gampad/clk?id=121051231&iu=/4140/ostg.clktrk