Re: [PATCH v2 4/9] blk-mq-debugfs: warn about possible deadlock

Re: [PATCH v2 4/9] blk-mq-debugfs: warn about possible deadlock

[kernel test robot]

Hi Yu,

kernel test robot noticed the following build errors:

[auto build test ERROR on axboe/for-next]
[also build test ERROR on linus/master v6.18-rc6 next-20251121]
[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#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Yu-Kuai/blk-mq-debugfs-factor-out-a-helper-to-register-debugfs-for-all-rq_qos/20251121-143315
base:   https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux.git for-next
patch link:    https://lore.kernel.org/r/20251121062829.1433332-5-yukuai%40fnnas.com
patch subject: [PATCH v2 4/9] blk-mq-debugfs: warn about possible deadlock
config: sparc64-defconfig (https://download.01.org/0day-ci/archive/20251122/202511221056.dAY0duWw-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251122/202511221056.dAY0duWw-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202511221056.dAY0duWw-lkp@intel.com/

All errors (new ones prefixed by >>):

>> block/blk-mq-debugfs.c:628:30: error: no member named 'blkcg_mutex' in 'struct request_queue'
     628 |         lockdep_assert_not_held(&q->blkcg_mutex);
         |                                  ~  ^
   include/linux/lockdep.h:393:49: note: expanded from macro 'lockdep_assert_not_held'
     393 | #define lockdep_assert_not_held(l)              do { (void)(l); } while (0)
         |                                                             ^
   1 error generated.


vim +628 block/blk-mq-debugfs.c

   612	
   613	static void debugfs_create_files(struct request_queue *q, struct dentry *parent,
   614					 void *data,
   615					 const struct blk_mq_debugfs_attr *attr)
   616	{
   617		/*
   618		 * Creating new debugfs entries with queue freezed has the risk of
   619		 * deadlock.
   620		 */
   621		WARN_ON_ONCE(q->mq_freeze_depth != 0);
   622		/*
   623		 * debugfs_mutex should not be nested under other locks that can be
   624		 * grabbed while queue is frozen.
   625		 */
   626		lockdep_assert_not_held(&q->elevator_lock);
   627		lockdep_assert_not_held(&q->rq_qos_mutex);
 > 628		lockdep_assert_not_held(&q->blkcg_mutex);
   629	
   630		if (IS_ERR_OR_NULL(parent))
   631			return;
   632	
   633		for (; attr->name; attr++)
   634			debugfs_create_file_aux(attr->name, attr->mode, parent,
   635					    (void *)attr, data, &blk_mq_debugfs_fops);
   636	}
   637	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH v2 4/9] blk-mq-debugfs: warn about possible deadlock

[Yu Kuai]

Hi,


在 2025/11/22 10:50, kernel test robot 写道:
> Hi Yu,
>
> kernel test robot noticed the following build errors:
>
> [auto build test ERROR on axboe/for-next]
> [also build test ERROR on linus/master v6.18-rc6 next-20251121]
> [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#_base_tree_information]
>
> url:    https://github.com/intel-lab-lkp/linux/commits/Yu-Kuai/blk-mq-debugfs-factor-out-a-helper-to-register-debugfs-for-all-rq_qos/20251121-143315
> base:   https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux.git for-next
> patch link:    https://lore.kernel.org/r/20251121062829.1433332-5-yukuai%40fnnas.com
> patch subject: [PATCH v2 4/9] blk-mq-debugfs: warn about possible deadlock
> config: sparc64-defconfig (https://download.01.org/0day-ci/archive/20251122/202511221056.dAY0duWw-lkp@intel.com/config)
> compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251122/202511221056.dAY0duWw-lkp@intel.com/reproduce)
>
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202511221056.dAY0duWw-lkp@intel.com/
>
> All errors (new ones prefixed by >>):
>
>>> block/blk-mq-debugfs.c:628:30: error: no member named 'blkcg_mutex' in 'struct request_queue'
>       628 |         lockdep_assert_not_held(&q->blkcg_mutex);
>           |                                  ~  ^
>     include/linux/lockdep.h:393:49: note: expanded from macro 'lockdep_assert_not_held'
>       393 | #define lockdep_assert_not_held(l)              do { (void)(l); } while (0)
>           |                                                             ^
>     1 error generated.
>
>
> vim +628 block/blk-mq-debugfs.c
>
>     612	
>     613	static void debugfs_create_files(struct request_queue *q, struct dentry *parent,
>     614					 void *data,
>     615					 const struct blk_mq_debugfs_attr *attr)
>     616	{
>     617		/*
>     618		 * Creating new debugfs entries with queue freezed has the risk of
>     619		 * deadlock.
>     620		 */
>     621		WARN_ON_ONCE(q->mq_freeze_depth != 0);
>     622		/*
>     623		 * debugfs_mutex should not be nested under other locks that can be
>     624		 * grabbed while queue is frozen.
>     625		 */
>     626		lockdep_assert_not_held(&q->elevator_lock);
>     627		lockdep_assert_not_held(&q->rq_qos_mutex);
>   > 628		lockdep_assert_not_held(&q->blkcg_mutex);
>     629	
>     630		if (IS_ERR_OR_NULL(parent))
>     631			return;
>     632	
>     633		for (; attr->name; attr++)
>     634			debugfs_create_file_aux(attr->name, attr->mode, parent,
>     635					    (void *)attr, data, &blk_mq_debugfs_fops);
>     636	}
>     637	

Thanks for the test, this set was build on the top of my other thread to introduce
blkcg_mutex, I'll rebase in the next version.


-- 
Thanks,
Kuai