On Fri, 2014-06-13 at 14:26 +0400, Denis Kirjanov wrote: > On 6/13/14, Catalin Marinas <catalin.marinas@xxxxxxx> wrote: > > On Fri, Jun 13, 2014 at 08:12:08AM +0100, Denis Kirjanov wrote: > >> On 6/12/14, Catalin Marinas <catalin.marinas@xxxxxxx> wrote: > >> > 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. > >> > >> 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] [<c000000000afc3dc>] > >> .memblock_alloc_range_nid+0x68/0x88 > >> [ 179.466544] [<c000000000afc444>] .memblock_alloc_base+0x20/0x58 > >> [ 179.466553] [<c000000000ae96cc>] .alloc_dart_table+0x5c/0xb0 > >> [ 179.466561] [<c000000000aea300>] .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) > > Ok, your path fixes the oops. > > Ben, can you shed some light on this issue? (I'm not Ben) Yes, the memory for dart_tablebase is removed from the linear mapping. In fact it's never mapped, see htab_initialize(). I don't easily see how commit d4c54919ed8, could have exposed this, but I don't know enough of the kmemleak internals to say for sure. cheers -- 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>