linux-kernel - Re: b276527539 ("staging: most: move core files out of the staging .."): [ 12.247349] BUG: kernel NULL pointer dereference, address: 00000000

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Date:   Fri, 24 Apr 2020 09:41:36 +0000
From:   <Christian.Gromm@...rochip.com>
To:     <lkp@...el.com>
CC:     <linux-kernel@...r.kernel.org>, <lkp@...ts.01.org>,
        <gregkh@...uxfoundation.org>, <devel@...verdev.osuosl.org>
Subject: Re: b276527539 ("staging: most: move core files out of the staging
 .."): [   12.247349] BUG: kernel NULL pointer dereference, address: 00000000

On Sun, 2020-03-29 at 21:39 +0800, kernel test robot wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you
> know the content is safe
> 
> Greetings,
> 
> 0day kernel testing robot got the below dmesg and the first bad
> commit is
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git
> staging-next
> 
> commit b276527539188f1f61c082ebef27803db93e536d
> Author:     Christian Gromm <christian.gromm@...rochip.com>
> AuthorDate: Tue Mar 10 14:02:40 2020 +0100
> Commit:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> CommitDate: Tue Mar 24 13:42:44 2020 +0100
> 
>     staging: most: move core files out of the staging area
> 
>     This patch moves the core module to the /drivers/most directory
>     and makes all necessary changes in order to not break the build.
> 
>     Signed-off-by: Christian Gromm <christian.gromm@...rochip.com>
>     Link: 
> https://lore.kernel.org/r/1583845362-26707-2-git-send-email-christian.gromm@microchip.com
>     Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> 
> 22dd4acc80  Staging: speakup: Add identifier name to function
> declaration arguments.
> b276527539  staging: most: move core files out of the staging area
> e681bb287f  staging: vt6656: Use DIV_ROUND_UP macro instead of
> specific code
> +-------------------------------------------------------+----------
> --+------------+------------+
> >                                                       | 22dd4acc80
> > | b276527539 | e681bb287f |
> +-------------------------------------------------------+----------
> --+------------+------------+
> > boot_successes                                        |
> > 26         | 0          | 0          |
> > boot_failures                                         |
> > 8          | 11         | 11         |
> > WARNING:possible_circular_locking_dependency_detected |
> > 8          |            |            |
> > BUG:kernel_NULL_pointer_dereference,address           |
> > 0          | 11         | 11         |
> > Oops:#[##]                                            |
> > 0          | 11         | 11         |
> > EIP:__list_add_valid                                  |
> > 0          | 11         | 11         |
> > Kernel_panic-not_syncing:Fatal_exception              |
> > 0          | 11         | 11         |
> +-------------------------------------------------------+----------
> --+------------+------------+
> 
> If you fix the issue, kindly add following tag
> Reported-by: kernel test robot <lkp@...el.com>
> 
> [   12.242090] no options.
> [   12.245364] FPGA DOWNLOAD --->
> [   12.245723] FPGA image file name: xlinx_fpga_firmware.bit
> [   12.246548] GPIO INIT FAIL!!
> [   12.246995] most_sound: init()
> [   12.247349] BUG: kernel NULL pointer dereference, address: 


The init order of the modules is wrong in case the driver is
being built in-tree.

The init function of module most_sound is called before the
core itself is being initialized.

[    5.179189] most_sound: init()
[    5.180205] mostcore: __init()

Hence the list used in the core to store and track the
registered components has not been initialized with
INIT_LIST_HEAD(&comp_list) by the time the sound module
tries to register itself with the core.

The Kconfig of most_sound, however, has a dependency to
MOST. How can the build system be forced to initialize the
core module first?

thanks,
Chris