From mboxrd@z Thu Jan 1 00:00:00 1970 From: dwoods@mellanox.com (David Woods) Date: Thu, 10 Mar 2016 17:23:18 -0500 Subject: BUG in HugeTLBFS with Contiguous hint In-Reply-To: References: <20160309021252.GA4573@linaro.org> <20160309153131.GF28496@arm.com> <56E048E6.9030508@mellanox.com> Message-ID: <56E1F3D6.9020906@mellanox.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 03/10/2016 02:57 AM, Steve Capper wrote: > Hi, > Replying to both inline below: > > On 9 March 2016 at 23:01, David Woods wrote: >> On 03/09/2016 10:31 AM, Will Deacon wrote: >>> On Wed, Mar 09, 2016 at 02:12:56AM +0000, Steve Capper wrote: >>>> Hi, >>> Hi Steve, >>> >>>> I am very sorry for the very late bug report. I have just come across >>>> this error. >>>> >>>> Whilst testing something else, I found that 2MB HugeTLB pages formed >>>> from contiguous pte's cause BUGs to appear when running through the >>>> libhugetlbfs test suite. >>> Ouch. Any idea why this wasn't spotted earlier? Did something else >>> change? > Sorry, no. A lot of stuff has changed (and I need to double check my > .config too). I will be able to dig into this in more detail when I > get back in the office next week (I have a painfully slow internet > connection to my devboard at the moment). I was able to verify that this is a regression. I did a git bisect to track it down and it looks like the commit which caused this failure was 61f5d698 mm: re-enable THP. The BUG does go away if TRANSPARENT_HUGEPAGE is disabled. I believe that means the problem came with any one of the 25 commits between 61f5d698 and 56a17b88 mm: temporarily mark THP broken. I'll continue to try to debug it. -Dave