From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from b.ns.miles-group.at ([95.130.255.144] helo=radon.swed.at) by merlin.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1WDgjL-0000ke-3j for linux-mtd@lists.infradead.org; Wed, 12 Feb 2014 20:48:28 +0000 Message-ID: <52FBDE01.9030207@nod.at> Date: Wed, 12 Feb 2014 21:48:01 +0100 From: Richard Weinberger MIME-Version: 1.0 To: Bill Pringlemeir , "Wiedemer, Thorsten (Lawo AG)" Subject: Re: UBI leb_write_unlock NULL pointer Oops (continuation) References: <52EF772D.8080207@nod.at> <52EF9FFE.4020405@nod.at> <52F1F658.9080701@nod.at> <87zjlxy8lj.fsf@nbsps.com> <87txc4w698.fsf@nbsps.com> <87ppmsw5sw.fsf@nbsps.com> In-Reply-To: <87ppmsw5sw.fsf@nbsps.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: "linux-mtd@lists.infradead.org" List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Am 12.02.2014 19:21, schrieb Bill Pringlemeir: > > On 12 Feb 2014, bpringlemeir@nbsps.com wrote: > >> We have 'IRQs off', which makes sense for __up_write. Trying >> 'ftrace_dump_on_oops' as Richard suggests would be helpful to find out >> what went on before. It might also make sense to dump some >> 'rwsem_waiter' nodes on the error? It looks like '__up_write' might >> normally have an empty list? Certainly an non-empty 'rwsem_waiter' is >> going to trigger the condition more often? I guess I can look to see >> what might cause this, even if I can not reproduce it. The >> 'preemp_count' has been two every time you have this; is that true? > > Wouldn't a smaller MTD trigger the condition more often? It looks like > the locking is done per erase block and several files in the same erase > block with simultaneous reading/writing will trigger this kind of > effect? > > Does that sound right Richard? Will it matter if I use a fixed or > dynamic volume size? Can I make a small UBI/UbiFS MTD partition and use > that for testing? My dynamic partition is about 200MB big. Usually we > never come near filling it, so there is lots of opportunity to use other > erase blocks. Yeah, I had the same idea and setup a MTD using nandsim. So far I was unable to trigger the issue. Let's wait for more results from Thorsten. Thanks, //richard