Hung kernel on SD writeback while suspending to RAM

Hung kernel on SD writeback while suspending to RAM

[Alex Gonzalez]

Hi,

I am looking into suspend to RAM on a Freescale MX51 running a 2.6.31
kernel. The
system suspends and resumes OK except when an SD card is mounted.

What happens then is that it finds a page which is being written to disk
(writeback flag is set), so it waits forever in uninterruptible state for
the write to finish, which never happens.

I was expecting the filesystem sync previous to the tasks freezing to have
written all page caches to disk.

Any suggestion as to how to debug this forward?

Thanks in advance,
Alex

INFO: task sh:595 blocked for more than 120 seconds.
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
sh D c02be320 0 595 1 0x00000000
[<c02be320>] (schedule+0x300/0x344) from [<c02be388>]
(io_schedule+0x24/0x40)
[<c02be388>] (io_schedule+0x24/0x40) from [<c006fe18>]
(sync_page+0x38/0x40)
[<c006fe18>] (sync_page+0x38/0x40) from [<c02be68c>]
(__wait_on_bit+0x54/0x9c)
[<c02be68c>] (__wait_on_bit+0x54/0x9c) from [<c0070070>]
(wait_on_page_bit+0xb4/0xcc)
[<c0070070>] (wait_on_page_bit+0xb4/0xcc) from
[<c0075fc8>] (write_cache_pages+0x1fc/0x37c)
[<c0075fc8>] (write_cache_pages+0x1fc/0x37c) from
[<c00761ac>] (do_writepages+0x3c/0x54)
[<c00761ac>] (do_writepages+0x3c/0x54) from
[<c0070a80>] (__filemap_fdatawrite_range+0x64/0x6c)
[<c0070a80>] (__filemap_fdatawrite_range+0x64/0x6c) from
[<c00714c4>] (filemap_fdatawrite+0x28/0x30)
[<c00714c4>] (filemap_fdatawrite+0x28/0x30) from
[<c00714e4>] (filemap_write_and_wait+0x18/0x3c)
[<c00714e4>] (filemap_write_and_wait+0x18/0x3c) from
[<c00b2e68>] (fsync_bdev+0x18/0x38)
[<c00b2e68>] (fsync_bdev+0x18/0x38) from [<c013d3bc>]
(invalidate_partition+0x18/0x34)
[<c013d3bc>] (invalidate_partition+0x18/0x34) from [<c00ca6e0>]
(del_gendisk+0x28/0xc8)
[<c00ca6e0>] (del_gendisk+0x28/0xc8) from [<c01e4c88>]
(mmc_blk_remove+0x20/0x3c)
[<c01e4c88>] (mmc_blk_remove+0x20/0x3c) from [<c01e0688>]
(mmc_bus_remove+0x18/0x20)
[<c01e0688>] (mmc_bus_remove+0x18/0x20) from
[<c01872f8>] (__device_release_driver+0x64/0xa4)
[<c01872f8>] (__device_release_driver+0x64/0xa4) from
[<c01873dc>] (device_release_driver+0x1c/0x28)
[<c01873dc>] (device_release_driver+0x1c/0x28) from
[<c01869f8>] (bus_remove_device+0x9c/0xac)
[<c01869f8>] (bus_remove_device+0x9c/0xac) from [<c01852d0>]
(device_del+0x110/0x16c)
[<c01852d0>] (device_del+0x110/0x16c) from [<c01e073c>]
(mmc_remove_card+0x4c/0x60)
[<c01e073c>] (mmc_remove_card+0x4c/0x60) from [<c01e1b70>]
(mmc_sd_remove+0x24/0x30)
[<c01e1b70>] (mmc_sd_remove+0x24/0x30) from [<c01e001c>]
(mmc_suspend_host+0xc4/0x188)
[<c01e001c>] (mmc_suspend_host+0xc4/0x188) from [<c01e6860>]
(sdhci_suspend+0x58/0x120)
[<c01e6860>] (sdhci_suspend+0x58/0x120) from
[<c0188378>] (platform_pm_suspend+0x48/0x54)
[<c0188378>] (platform_pm_suspend+0x48/0x54) from [<c018a098>]
(pm_op+0x30/0x7c)
[<c018a098>] (pm_op+0x30/0x7c) from [<c018a86c>]
(dpm_suspend_start+0x3ac/0x50c)
[<c018a86c>] (dpm_suspend_start+0x3ac/0x50c) from
[<c006b560>] (suspend_devices_and_enter+0x3c/0x1c4)
[<c006b560>] (suspend_devices_and_enter+0x3c/0x1c4) from
[<c006b7a0>] (enter_state+0xb8/0x118)
[<c006b7a0>] (enter_state+0xb8/0x118) from [<c006afbc>]
(state_store+0xa0/0xbc)  [<c006afbc>] (state_store+0xa0/0xbc) from
[<c0146cd4>] (kobj_attr_store+0x18/0x1c)
[<c0146cd4>] (kobj_attr_store+0x18/0x1c) from
[<c00cbd24>] (sysfs_write_file+0x108/0x13c)
[<c00cbd24>] (sysfs_write_file+0x108/0x13c) from [<c008f7cc>]
(vfs_write+0xac/0x128)  [<c008f7cc>] (vfs_write+0xac/0x128) from
[<c008f8f4>] (sys_write+0x3c/0x68)
[<c008f8f4>] (sys_write+0x3c/0x68) from [<c0025e80>] (ret_fast_
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Hung kernel on SD writeback while suspending to RAM

[Eric Bénard]

Hi,

Le 15/06/2010 09:58, Alex Gonzalez a ?crit :
> I am looking into suspend to RAM on a Freescale MX51 running a 2.6.31
> kernel. The
> system suspends and resumes OK except when an SD card is mounted.
>
> What happens then is that it finds a page which is being written to disk
> (writeback flag is set), so it waits forever in uninterruptible state
> for the write to finish, which never happens.
>
> I was expecting the filesystem sync previous to the tasks freezing to
> have written all page caches to disk.
>
> Any suggestion as to how to debug this forward?
>
I think you need to enable
[ ] Assume MMC/SD cards are non-removable (DANGEROUS)
in order to be able to suspend / resume a mounted SDCard.

Eric

Hung kernel on SD writeback while suspending to RAM

[Matt Reimer]

On Thu, Jun 17, 2010 at 9:25 AM, Eric B?nard <eric@eukrea.com> wrote:
> Hi,
>
> Le 15/06/2010 09:58, Alex Gonzalez a ?crit :
>>
>> I am looking into suspend to RAM on a Freescale MX51 running a 2.6.31
>> kernel. The
>> system suspends and resumes OK except when an SD card is mounted.
>>
>> What happens then is that it finds a page which is being written to disk
>> (writeback flag is set), so it waits forever in uninterruptible state
>> for the write to finish, which never happens.
>>
>> I was expecting the filesystem sync previous to the tasks freezing to
>> have written all page caches to disk.
>>
>> Any suggestion as to how to debug this forward?
>>
> I think you need to enable
> [ ] Assume MMC/SD cards are non-removable (DANGEROUS)
> in order to be able to suspend / resume a mounted SDCard.

Also see the thread "[PATCH] Fix the outstanding issue with hangs on
insert/removal of mmc cards" on linux-mmc:

http://article.gmane.org/gmane.linux.kernel.mmc/2233

Matt

Hung kernel on SD writeback while suspending to RAM

[Alex Gonzalez]

Hi Eric,

That indeed did the trick.

The Kconfig help confused me as I was neither removing the card from
the slot or booting from it.

Thanks a lot,
Alex

--------------------------------

If you say Y here, the MMC layer will assume that all cards
stayed in their respective slots during the suspend. The
normal behaviour is to remove them at suspend and
redetecting them at resume.

This option is usually just for embedded systems which use
a MMC/SD card for rootfs. Most people should say N here.


On Thu, Jun 17, 2010 at 6:25 PM, Eric B?nard <eric@eukrea.com> wrote:
> Hi,
>
> Le 15/06/2010 09:58, Alex Gonzalez a ?crit :
>>
>> I am looking into suspend to RAM on a Freescale MX51 running a 2.6.31
>> kernel. The
>> system suspends and resumes OK except when an SD card is mounted.
>>
>> What happens then is that it finds a page which is being written to disk
>> (writeback flag is set), so it waits forever in uninterruptible state
>> for the write to finish, which never happens.
>>
>> I was expecting the filesystem sync previous to the tasks freezing to
>> have written all page caches to disk.
>>
>> Any suggestion as to how to debug this forward?
>>
> I think you need to enable
> [ ] Assume MMC/SD cards are non-removable (DANGEROUS)
> in order to be able to suspend / resume a mounted SDCard.
>
> Eric
>