On Thu, Jun 12, 2014 at 01:00:57PM +0100, Denis Kirjanov wrote: > On 6/12/14, Denis Kirjanov <kda@xxxxxxxxxxxxxxxxx> wrote: > > On 6/12/14, Catalin Marinas <catalin.marinas@xxxxxxx> wrote: > >> On 11 Jun 2014, at 21:04, Denis Kirjanov <kda@xxxxxxxxxxxxxxxxx> wrote: > >>> On 6/11/14, Catalin Marinas <catalin.marinas@xxxxxxx> 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 it’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. -- Catalin -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>