Re: OOM killer, page fault

From: Norbert Preining
Date: Thu Nov 05 2009 - 08:21:21 EST

Hi Kim, hi all,

(still please Cc)

sorry for the late reply. I have two news, one good and one bad: The good
being that I can reproduce the bug by running VirtualBox with some W7
within. Anyway, I don't have a trace or better debug due to the bad news:
Both 2.6.32-rc5 and 2.6.32-rc6 do *not* boot with the patch below.
Don't ask me why, please, and I don't have a serial/net console so that
I can tell you more, but the booting hangs badly at:
[ 6.657492] usb 4-1: Product: Globetrotter HSDPA Modem
[ 6.657494] usb 4-1: Manufacturer: Option N.V.
[ 6.657496] usb 4-1: SerialNumber: Serial Number
[ 6.657558] usb 4-1: configuration #1 chosen from 1 choice
[ 6.837364] input: PS/2 Mouse as /devices/platform/i8042/serio2/input/input6
[ 6.853693] input: AlpsPS/2 ALPS GlidePoint as /devices/platform/i8042/serio2/input/input7

Normally it continues like that, but with the patch below it hangs here
and does not continue. I need to Sysrq-s/u/b out of it.

[ 6.904119] usb 8-2: new full speed USB device using uhci_hcd and address 2
[ 7.075524] usb 8-2: New USB device found, idVendor=044e, idProduct=3017

> diff --git a/mm/memory.c b/mm/memory.c
> index 7e91b5f..47e4b15 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -2713,7 +2713,11 @@ static int __do_fault(struct mm_struct *mm,
> struct vm_area_struct *vma,
> = NULL;
> ret = vma->vm_ops->fault(vma, &vmf);
> - if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))
> + if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE))) {
> + printk(KERN_DEBUG "vma->vm_ops->fault : 0x%lx\n",
> vma->vm_ops->fault);
> + WARN_ON(1);
> +
> + }
> return ret;
> if (unlikely(PageHWPoison( {

I know it sounds completely crazy, the patch only does harmless things
afais. But I tried it. Several times. rc6+patch never did boot, while
rc5 without path did boot. Then I patched it into -rc5, recompiled, and
boom, no boot. booting into .31.5, recompiling rc6 and rc5 without
that patch and suddenly rc6 boots (and I am sure rc5, too).

Sorry that I cannot give more infos, please let me know what else I can

Ah yes, I can reproduce the original strange bug with oom killer!

Best wishes


Dr. Norbert Preining Associate Professor
JAIST Japan Advanced Institute of Science and Technology preining@xxxxxxxxxxx
Vienna University of Technology preining@xxxxxxxx
Debian Developer (Debian TeX Task Force) preining@xxxxxxxxxx
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