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Message-ID: <20140613085640.GA21018@arm.com> Date: Fri, 13 Jun 2014 09:56:40 +0100 From: Catalin Marinas <catalin.marinas@....com> To: Denis Kirjanov <kda@...ux-powerpc.org> Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "linux-mm@...ck.org" <linux-mm@...ck.org>, Naoya Horiguchi <n-horiguchi@...jp.nec.com>, linuxppc-dev@...ts.ozlabs.org, Benjamin Herrenschmidt <benh@...nel.crashing.org>, Paul Mackerras <paulus@...ba.org> Subject: Re: kmemleak: Unable to handle kernel paging request On Fri, Jun 13, 2014 at 08:12:08AM +0100, Denis Kirjanov wrote: > On 6/12/14, Catalin Marinas <catalin.marinas@....com> wrote: > > On Thu, Jun 12, 2014 at 01:00:57PM +0100, Denis Kirjanov wrote: > >> On 6/12/14, Denis Kirjanov <kda@...ux-powerpc.org> wrote: > >> > On 6/12/14, Catalin Marinas <catalin.marinas@....com> wrote: > >> >> On 11 Jun 2014, at 21:04, Denis Kirjanov <kda@...ux-powerpc.org> > >> >> wrote: > >> >>> On 6/11/14, Catalin Marinas <catalin.marinas@....com> 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) ---------------8<-------------------------- >From 09a7f1c97166c7bdca7ca4e8a4ff2774f3706ea3 Mon Sep 17 00:00:00 2001 From: Catalin Marinas <catalin.marinas@....com> 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@....com> Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org> Cc: Paul Mackerras <paulus@...ba.org> --- 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 from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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