Re: mmotm 2015-01-22-15-04: qemu failures due to 'mm: account pmd page tables to the process'

From: Guenter Roeck <linux@roeck-us.net>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	linux-fsdevel@vger.kernel.org, linux-next@vger.kernel.org,
	sfr@canb.auug.org.au, mhocko@suse.cz,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Subject: Re: mmotm 2015-01-22-15-04: qemu failures due to 'mm: account pmd page tables to the process'
Date: Fri, 23 Jan 2015 18:44:58 -0800	[thread overview]
Message-ID: <54C3072A.1030604@roeck-us.net> (raw)
In-Reply-To: <20150123135519.9f1061caf875f41f89298d59@linux-foundation.org>

On 01/23/2015 01:55 PM, Andrew Morton wrote:
> On Fri, 23 Jan 2015 07:07:56 -0800 Guenter Roeck <linux@roeck-us.net> wrote:
>
>>>>
>>>> qemu:microblaze generates warnings to the console.
>>>>
>>>> WARNING: CPU: 0 PID: 32 at mm/mmap.c:2858 exit_mmap+0x184/0x1a4()
>>>>
>>>> with various call stacks. See
>>>> http://server.roeck-us.net:8010/builders/qemu-microblaze-mmotm/builds/15/steps/qemubuildcommand/logs/stdio
>>>> for details.
>>>
>>> Could you try patch below? Completely untested.
>>>
>>> >From b584bb8d493794f67484c0b57c161d61c02599bc Mon Sep 17 00:00:00 2001
>>> From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
>>> Date: Fri, 23 Jan 2015 13:08:26 +0200
>>> Subject: [PATCH] microblaze: define __PAGETABLE_PMD_FOLDED
>>>
>>> Microblaze uses custom implementation of PMD folding, but doesn't define
>>> __PAGETABLE_PMD_FOLDED, which generic code expects to see. Let's fix it.
>>>
>>> Defining __PAGETABLE_PMD_FOLDED will drop out unused __pmd_alloc().
>>> It also fixes problems with recently-introduced pmd accounting.
>>>
>>> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
>>> Reported-by: Guenter Roeck <linux@roeck-us.net>
>>
>> Tested working.
>>
>> Tested-by: Guenter Roeck <linux@roeck-us.net>
>>
>> Any idea how to fix the sh problem ?
>
> Can you tell us more about it?  All I'm seeing is "qemu:sh fails to
> shut down", which isn't very clear.
>

qemu command line:

/opt/buildbot/bin/qemu-system-sh4 -M r2d -kernel ./arch/sh/boot/zImage \
         -drive file=rootfs.ext2,if=ide \
         -append "root=/dev/sda console=ttySC1,115200 noiotrap"
         -serial null -serial stdio -net nic,model=rtl8139 -net user
         -nographic -monitor null

--
Poweroff log in mainline (v3.19-rc5-119-gb942c65):

/ # poweroff
The system is going down NOW!
Sent SIGTERM to all processes
Sent SIGKILL to all processes
Requesting system poweroff
sd 0:0:0:0: [sda] Synchronizing SCSI cache
sd 0:0:0:0: [sda] Stopping disk
reboot: Power down

--
Poweroff log in mmotm (v3.19-rc5-417-gc64429b):

/ # poweroff

[ nothing else happens until I kill the qemu session ]

The "halt" command does not work either.

--
The message "The system is going down NOW" is from the init process.
If I use "kill -12 1" instead of "halt" or "poweroff", the system does
shut down as expected. "poweroff -f" also works.

Trying to debug this further, I noticed that the "ps" command hangs
as well, so the problem is not limited to poweroff or halt.

I'll be happy to debug this further, I just have no idea where to start.

Thanks,
Guenter