From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wg0-f47.google.com (mail-wg0-f47.google.com [74.125.82.47]) by kanga.kvack.org (Postfix) with ESMTP id 949996B00A3 for ; Fri, 13 Jun 2014 04:56:57 -0400 (EDT) Received: by mail-wg0-f47.google.com with SMTP id k14so2406634wgh.30 for ; Fri, 13 Jun 2014 01:56:56 -0700 (PDT) Received: from collaborate-mta1.arm.com (fw-tnat.austin.arm.com. [217.140.110.23]) by mx.google.com with ESMTP id j10si926745wiy.81.2014.06.13.01.56.55 for ; Fri, 13 Jun 2014 01:56:55 -0700 (PDT) Date: Fri, 13 Jun 2014 09:56:40 +0100 From: Catalin Marinas Subject: Re: kmemleak: Unable to handle kernel paging request Message-ID: <20140613085640.GA21018@arm.com> References: <20140611173851.GA5556@MacBook-Pro.local> <20140612143916.GB8970@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Denis Kirjanov Cc: "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , Naoya Horiguchi , linuxppc-dev@lists.ozlabs.org, Benjamin Herrenschmidt , Paul Mackerras On Fri, Jun 13, 2014 at 08:12:08AM +0100, Denis Kirjanov wrote: > On 6/12/14, Catalin Marinas wrote: > > On Thu, Jun 12, 2014 at 01:00:57PM +0100, Denis Kirjanov wrote: > >> On 6/12/14, Denis Kirjanov wrote: > >> > On 6/12/14, Catalin Marinas wrote: > >> >> On 11 Jun 2014, at 21:04, Denis Kirjanov > >> >> wrote: > >> >>> On 6/11/14, Catalin Marinas wrote: > >> >>>> On Wed, Jun 11, 2014 at 04:13:07PM +0400, Denis Kirjanov wrote: > >> >>>>> I got a trace while running 3.15.0-08556-gdfb9454: > >> >>>>> > >> >>>>> [ 104.534026] Unable to handle kernel paging request for data at > >> >>>>> address 0xc00000007f000000 > >> >>>> > >> >>>> Were there any kmemleak messages prior to this, like "kmemleak > >> >>>> disabled"? There could be a race when kmemleak is disabled because > >> >>>> of > >> >>>> some fatal (for kmemleak) error while the scanning is taking place > >> >>>> (which needs some more thinking to fix properly). > >> >>> > >> >>> No. I checked for the similar problem and didn't find anything > >> >>> relevant. > >> >>> I'll try to bisect it. > >> >> > >> >> Does this happen soon after boot? I guess ita??s the first scan > >> >> (scheduled at around 1min after boot). Something seems to be telling > >> >> kmemleak that there is a valid memory block at 0xc00000007f000000. > >> > > >> > Yeah, it happens after a while with a booted system so that's the > >> > first kmemleak scan. > >> > >> I've bisected to this commit: d4c54919ed86302094c0ca7d48a8cbd4ee753e92 > >> "mm: add !pte_present() check on existing hugetlb_entry callbacks". > >> Reverting the commit fixes the issue > > > > I can't figure how this causes the problem but I have more questions. Is > > 0xc00000007f000000 address always the same in all crashes? If yes, you > > could comment out start_scan_thread() in kmemleak_late_init() to avoid > > the scanning thread starting. Once booted, you can run: > > > > echo dump=0xc00000007f000000 > /sys/kernel/debug/kmemleak > > > > and check the dmesg for what kmemleak knows about that address, when it > > was allocated and whether it should be mapped or not. > > The address is always the same. > > [ 179.466239] kmemleak: Object 0xc00000007f000000 (size 16777216): > [ 179.466503] kmemleak: comm "swapper/0", pid 0, jiffies 4294892300 > [ 179.466508] kmemleak: min_count = 0 > [ 179.466512] kmemleak: count = 0 > [ 179.466517] kmemleak: flags = 0x1 > [ 179.466522] kmemleak: checksum = 0 > [ 179.466526] kmemleak: backtrace: > [ 179.466531] [] .memblock_alloc_range_nid+0x68/0x88 > [ 179.466544] [] .memblock_alloc_base+0x20/0x58 > [ 179.466553] [] .alloc_dart_table+0x5c/0xb0 > [ 179.466561] [] .pmac_probe+0x38/0xa0 > [ 179.466569] [<000000000002166c>] 0x2166c > [ 179.466579] [<0000000000ae0e68>] 0xae0e68 > [ 179.466587] [<0000000000009bc4>] 0x9bc4 OK, so that's the DART table allocated via alloc_dart_table(). Is dart_tablebase removed from the kernel linear mapping after allocation? If that's the case, we need to tell kmemleak to ignore this block (see patch below, untested). But I still can't explain how commit d4c54919ed863020 causes this issue. (also cc'ing the powerpc list and maintainers) ---------------8<--------------------------