linux-kernel - Re: task kworker / kloopd blocked for more than 120 seconds

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Message-ID: <CACVXFVNTp5oqek3XtoiJ63AqTCWUGSBnWC+DD7YMjTMUs1N3GQ@mail.gmail.com>
Date:	Thu, 28 May 2015 20:20:54 +0800
From:	Ming Lei <tom.leiming@...il.com>
To:	Christian Hesse <list@...rm.de>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: task kworker / kloopd blocked for more than 120 seconds

Hello Christian,

On Thu, May 28, 2015 at 5:37 PM, Christian Hesse <list@...rm.de> wrote:
> Hello everybody,
>
> I am experiencing issues on a live system based on Arch Linux [0][1] with
> Linux kernel 4.0.x when booted in RAM mode (parameter 'copytoram') [2].
> Probably the problem exists some time longer, I am not sure when this first
> happened and what versions are effected.
>
> The boot sequence looks like this:
>
> -> boot kernel
> -> start initramfs
> -> get the squashfs image file (there is no difference with loop mount,
>    nbd or http)
> -> root filesystem is set up with loop devices and device mapper
> -> boot continues
>
> The root filesystem is accessed as follows:
>
> -> ext4 filesystem
>   -> device mapper snapshot target
>     -> /dev/loop1: r/o ext4 image
>       -> mounted squashfs
>         -> /dev/loop0: squashfs image
>     -> /dev/loop2: r/w COW image (sparse file)
>
>
> Assembling the root filesystem stack always succeeds, but sometimes boot hangs
> with a lot of:

Could you try the following two patches to see if they can fix your issue?

http://git.kernel.org/cgit/linux/kernel/git/axboe/linux-block.git/commit/?h=for-next&id=f4aa4c7bbac6c4afdd4adccf90898c1a3685396d

http://git.kernel.org/cgit/linux/kernel/git/axboe/linux-block.git/commit/?h=for-next&id=4d4e41aef9429872ea3b105e83426941f7185ab6

Thanks,
Ming

>
> INFO: task kworker/u#:#:### blocked for more than 120 seconds
>
> and a single:
>
> INFO: task kloopd/### blocked for more than 120 seconds
>
> Any idea what goes wrong? Looks like a race condition or deadlock.
>
> [0] https://wiki.archlinux.org/index.php/Archiso
> [1] https://projects.archlinux.org/archiso.git/
> [2] https://projects.archlinux.org/archiso.git/tree/docs/README.bootparams
> --
> main(a){char*c=/*    Schoene Gruesse                         */"B?IJj;MEH"
> "CX:;",b;for(a/*    Chris           get my mail address:    */=0;b=c[a++];)
> putchar(b-1/(/*               gcc -o sig sig.c && ./sig    */b/42*2-3)*42);}



-- 
Ming Lei
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