[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! Perhaps something to improve:
> 
> [auto build test WARNING on next-20210813]
> [also build test WARNING 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: arc-randconfig-r031-20210815 (attached as .config)
> compiler: arceb-elf-gcc (GCC) 11.2.0
> reproduce (this is a W=1 build):
>          wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>          chmod +x ~/bin/make.cross
>          # 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
>          COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross ARCH=arc
> 
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp at intel.com>
> 
> All warnings (new ones prefixed by >>):
> 
>>> drivers/gpu/drm/drm_auth.c:483:6: warning: no previous prototype for 'master_flush' [-Wmissing-prototypes]
>       483 | void master_flush(struct callback_head *cb)
>           |      ^~~~~~~~~~~~
> 

My bad, this should have been declared with static. I'll add it in, thanks.

> 
> vim +/master_flush +483 drivers/gpu/drm/drm_auth.c
> 
>     479	
>     480	/* After flushing, all readers that might have seen old master/lease
>     481	 * permissions are guaranteed to have completed.
>     482	 */
>   > 483	void master_flush(struct callback_head *cb)
>     484	{
>     485		struct drm_device *dev = container_of(cb, struct drm_device,
>     486						      master_flush_work);
>     487	
>     488		down_write(&dev->master_rwsem);
>     489		up_write(&dev->master_rwsem);
>     490	}
>     491	
> 
> ---
> 0-DAY CI Kernel Test Service, Intel Corporation
> https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
>