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? Thanks! > ---------------8<-------------------------- > > From 09a7f1c97166c7bdca7ca4e8a4ff2774f3706ea3 Mon Sep 17 00:00:00 2001 > From: Catalin Marinas <catalin.marinas@xxxxxxx> > Date: Fri, 13 Jun 2014 09:44:21 +0100 > Subject: [PATCH] powerpc/kmemleak: Do not scan the DART table > > The DART table allocation is registered to kmemleak via the > memblock_alloc_base() call. However, the DART table is later unmapped > and dart_tablebase VA no longer accessible. This patch tells kmemleak > not to scan this block and avoid an unhandled paging request. > > Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx> > Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx> > Cc: Paul Mackerras <paulus@xxxxxxxxx> > --- > arch/powerpc/sysdev/dart_iommu.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/arch/powerpc/sysdev/dart_iommu.c > b/arch/powerpc/sysdev/dart_iommu.c > index 62c47bb76517..9e5353ff6d1b 100644 > --- a/arch/powerpc/sysdev/dart_iommu.c > +++ b/arch/powerpc/sysdev/dart_iommu.c > @@ -476,6 +476,11 @@ void __init alloc_dart_table(void) > */ > dart_tablebase = (unsigned long) > __va(memblock_alloc_base(1UL<<24, 1UL<<24, 0x80000000L)); > + /* > + * The DART space is later unmapped from the kernel linear mapping and > + * accessing dart_tablebase during kmemleak scanning will fault. > + */ > + kmemleak_no_scan((void *)dart_tablebase); > > printk(KERN_INFO "DART table allocated at: %lx\n", dart_tablebase); > } > -- 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