From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: md deadlock (was Re: 2.6.18-mm2) Date: Fri, 29 Sep 2006 16:03:17 +0200 Message-ID: <1159538597.28131.97.camel@taijtu> References: <20060928014623.ccc9b885.akpm@osdl.org> <6bffcb0e0609280454n34d40c0la8786e1eba6dcdf3@mail.gmail.com> <1159531923.28131.80.camel@taijtu> <17693.5913.393686.223172@cse.unsw.edu.au> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <17693.5913.393686.223172@cse.unsw.edu.au> Sender: linux-raid-owner@vger.kernel.org To: Neil Brown Cc: Michal Piotrowski , Andrew Morton , Ingo Molnar , linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-raid.ids On Fri, 2006-09-29 at 22:52 +1000, Neil Brown wrote: > On Friday September 29, a.p.zijlstra@chello.nl wrote: > > On Thu, 2006-09-28 at 13:54 +0200, Michal Piotrowski wrote: > > > > Looks like a real deadlock here. It seems to me #2 is the easiest to > > break. > > I guess it could deadlock if you tried to add /dev/md0 as a component > of /dev/md0. I should probably check for that somewhere. > In other cases the array->member ordering ensures there is no > deadlock. > 1 2 open(/dev/md0) open(/dev/md0) - do_open() -> bdev->bd_mutex ioctl(/dev/md0, hotadd) - md_ioctl() -> mddev->reconfig_mutex -- hot_add_disk() --- bind_rdev_to_array() ---- bd_claim_by_disk() ----- bd_claim_by_kobject() -- md_open() --- mddev_lock() ---- mutex_lock(mddev->reconfig_mutex) ------ mutex_lock(bdev->bd_mutex) looks like an AB-BA deadlock to me