[PATCH v2] drm: avoid races with modesetting rights

[Desmond Cheong Zhi Xi]

On 16/8/21 2:47 am, kernel test robot wrote:
> Hi Desmond,
> 
> Thank you for the patch! Yet something to improve:
> 
> [auto build test ERROR on next-20210813]
> [also build test ERROR on v5.14-rc5]
> [cannot apply to linus/master v5.14-rc5 v5.14-rc4 v5.14-rc3]
> [If your patch is applied to the wrong git tree, kindly drop us a note.
> And when submitting patch, we suggest to use '--base' as documented in
> https://git-scm.com/docs/git-format-patch]
> 
> url:    https://github.com/0day-ci/linux/commits/Desmond-Cheong-Zhi-Xi/drm-avoid-races-with-modesetting-rights/20210815-234145
> base:    4b358aabb93a2c654cd1dcab1a25a589f6e2b153
> config: i386-randconfig-a004-20210815 (attached as .config)
> compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
> reproduce (this is a W=1 build):
>          # https://github.com/0day-ci/linux/commit/cf6d8354b7d7953cd866fad004cbb189adfa074f
>          git remote add linux-review https://github.com/0day-ci/linux
>          git fetch --no-tags linux-review Desmond-Cheong-Zhi-Xi/drm-avoid-races-with-modesetting-rights/20210815-234145
>          git checkout cf6d8354b7d7953cd866fad004cbb189adfa074f
>          # save the attached .config to linux build tree
>          make W=1 ARCH=i386
> 
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp at intel.com>
> 
> All errors (new ones prefixed by >>, old ones prefixed by <<):
> 
>>> ERROR: modpost: "task_work_add" [drivers/gpu/drm/drm.ko] undefined!
> 

I'm a bit uncertain about this. Looking into the .config used, this 
error seems to happen because task_work_add isn't an exported symbol, 
but DRM is being compiled as a loadable kernel module (CONFIG_DRM=m).

One way to deal with this is to export the symbol, but there was a 
proposed patch to do this a few months back that wasn't picked up [1], 
so I'm not sure what to make of this.

I'll export the symbol as part of a v3 series, and check in with the 
task-work maintainers.

Link: 
https://lore.kernel.org/lkml/20210127150029.13766-3-joshi.k@samsung.com/ [1]

> ---
> 0-DAY CI Kernel Test Service, Intel Corporation
> https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
>