drm: Fix possible deadlock in drm_mode_config_cleanup()

Message ID 20171213085720.6059-1-m.szyprowski@samsung.com
State New
Headers show
Series
  • drm: Fix possible deadlock in drm_mode_config_cleanup()
Related show

Commit Message

Marek Szyprowski Dec. 13, 2017, 8:57 a.m.
drm_mode_config_cleanup() might be called from a workqueue context (for
example in error path handling of deferred probe), so it must not call
flush_scheduled_work(), because it would deadlock in such case. Replace
that call with explicit counting of the scheduled connector free works
and waiting until it reaches zero.

Fixes: a703c55004e1 ("drm: safely free connectors from connector_iter")
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>

---
This fixes the issue discussed in the following thread:
https://www.spinics.net/lists/arm-kernel/msg622332.html
---
 drivers/gpu/drm/drm_connector.c   |  6 +++++-
 drivers/gpu/drm/drm_mode_config.c |  6 +++++-
 include/drm/drm_mode_config.h     | 13 +++++++++++++
 3 files changed, 23 insertions(+), 2 deletions(-)

-- 
2.15.0

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Comments

Chris Wilson Dec. 13, 2017, 9:03 a.m. | #1
Quoting Marek Szyprowski (2017-12-13 08:57:20)
> drm_mode_config_cleanup() might be called from a workqueue context (for

> example in error path handling of deferred probe), so it must not call

> flush_scheduled_work(), because it would deadlock in such case. Replace

> that call with explicit counting of the scheduled connector free works

> and waiting until it reaches zero.

> 

> Fixes: a703c55004e1 ("drm: safely free connectors from connector_iter")

> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>

> ---

> This fixes the issue discussed in the following thread:

> https://www.spinics.net/lists/arm-kernel/msg622332.html

> ---

>  drivers/gpu/drm/drm_connector.c   |  6 +++++-

>  drivers/gpu/drm/drm_mode_config.c |  6 +++++-

>  include/drm/drm_mode_config.h     | 13 +++++++++++++

>  3 files changed, 23 insertions(+), 2 deletions(-)

> 

> diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c

> index 0b7e0974e6da..7620ac1ad1b1 100644

> --- a/drivers/gpu/drm/drm_connector.c

> +++ b/drivers/gpu/drm/drm_connector.c

> @@ -161,6 +161,8 @@ static void drm_connector_free_work_fn(struct work_struct *work)

>  

>         drm_mode_object_unregister(dev, &connector->base);

>         connector->funcs->destroy(connector);

> +       atomic_dec(&dev->mode_config.connector_free_works);

> +       wake_up_all(&dev->mode_config.connector_free_queue);

>  }

>  

>  /**

> @@ -552,8 +554,10 @@ EXPORT_SYMBOL(drm_connector_list_iter_begin);

>  static void

>  drm_connector_put_safe(struct drm_connector *conn)

>  {

> -       if (refcount_dec_and_test(&conn->base.refcount.refcount))

> +       if (refcount_dec_and_test(&conn->base.refcount.refcount)) {

> +               atomic_inc(&conn->dev->mode_config.connector_free_works);

>                 schedule_work(&conn->free_work);

> +       }

>  }

>  

>  /**

> diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c

> index 6ffe952142e6..cca443faebd8 100644

> --- a/drivers/gpu/drm/drm_mode_config.c

> +++ b/drivers/gpu/drm/drm_mode_config.c

> @@ -381,6 +381,7 @@ void drm_mode_config_init(struct drm_device *dev)

>         idr_init(&dev->mode_config.tile_idr);

>         ida_init(&dev->mode_config.connector_ida);

>         spin_lock_init(&dev->mode_config.connector_list_lock);

> +       init_waitqueue_head(&dev->mode_config.connector_free_queue);

>  

>         drm_mode_create_standard_properties(dev);

>  

> @@ -431,8 +432,11 @@ void drm_mode_config_cleanup(struct drm_device *dev)

>                 drm_connector_put(connector);

>         }

>         drm_connector_list_iter_end(&conn_iter);

> +

>         /* connector_iter drops references in a work item. */

> -       flush_scheduled_work();

> +       wait_event(dev->mode_config.connector_free_queue,

> +                  !atomic_read(&dev->mode_config.connector_free_works));

> +

>         if (WARN_ON(!list_empty(&dev->mode_config.connector_list))) {

>                 drm_connector_list_iter_begin(dev, &conn_iter);

>                 drm_for_each_connector_iter(connector, &conn_iter)

> diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h

> index a0afeb591dcb..83a7db997e83 100644

> --- a/include/drm/drm_mode_config.h

> +++ b/include/drm/drm_mode_config.h

> @@ -413,6 +413,19 @@ struct drm_mode_config {

>          * &struct drm_connector_list_iter to walk this list.

>          */

>         struct list_head connector_list;

> +       /**

> +        * @pending_connector_free_works:

> +        *

> +        * Number of scheduled connector->free_work instances, see

> +        * drm_connector_put_safe().

> +        */

> +       atomic_t connector_free_works;

> +       /**

> +        * @pending_connector_free_queue:

> +        *

> +        * Wait queue for waiting until connector->free_work is finished.

> +        */

> +       wait_queue_head_t connector_free_queue;


Just move from a system_wq to a local wq?
-Chris
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Daniel Vetter Dec. 13, 2017, 10:45 a.m. | #2
On Wed, Dec 13, 2017 at 09:57:20AM +0100, Marek Szyprowski wrote:
> drm_mode_config_cleanup() might be called from a workqueue context (for

> example in error path handling of deferred probe), so it must not call

> flush_scheduled_work(), because it would deadlock in such case. Replace

> that call with explicit counting of the scheduled connector free works

> and waiting until it reaches zero.

> 

> Fixes: a703c55004e1 ("drm: safely free connectors from connector_iter")

> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>


I don't like hand-rolling wait stuff if it's avoidable (although
cross-release will catch all the fun nowadays). I'm working on a patch to
rework the cleanup logic so we can flush stuff directly. Bit more work,
but imo cleaner logic.
-Daniel
> ---

> This fixes the issue discussed in the following thread:

> https://www.spinics.net/lists/arm-kernel/msg622332.html

> ---

>  drivers/gpu/drm/drm_connector.c   |  6 +++++-

>  drivers/gpu/drm/drm_mode_config.c |  6 +++++-

>  include/drm/drm_mode_config.h     | 13 +++++++++++++

>  3 files changed, 23 insertions(+), 2 deletions(-)

> 

> diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c

> index 0b7e0974e6da..7620ac1ad1b1 100644

> --- a/drivers/gpu/drm/drm_connector.c

> +++ b/drivers/gpu/drm/drm_connector.c

> @@ -161,6 +161,8 @@ static void drm_connector_free_work_fn(struct work_struct *work)

>  

>  	drm_mode_object_unregister(dev, &connector->base);

>  	connector->funcs->destroy(connector);

> +	atomic_dec(&dev->mode_config.connector_free_works);

> +	wake_up_all(&dev->mode_config.connector_free_queue);

>  }

>  

>  /**

> @@ -552,8 +554,10 @@ EXPORT_SYMBOL(drm_connector_list_iter_begin);

>  static void

>  drm_connector_put_safe(struct drm_connector *conn)

>  {

> -	if (refcount_dec_and_test(&conn->base.refcount.refcount))

> +	if (refcount_dec_and_test(&conn->base.refcount.refcount)) {

> +		atomic_inc(&conn->dev->mode_config.connector_free_works);

>  		schedule_work(&conn->free_work);

> +	}

>  }

>  

>  /**

> diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c

> index 6ffe952142e6..cca443faebd8 100644

> --- a/drivers/gpu/drm/drm_mode_config.c

> +++ b/drivers/gpu/drm/drm_mode_config.c

> @@ -381,6 +381,7 @@ void drm_mode_config_init(struct drm_device *dev)

>  	idr_init(&dev->mode_config.tile_idr);

>  	ida_init(&dev->mode_config.connector_ida);

>  	spin_lock_init(&dev->mode_config.connector_list_lock);

> +	init_waitqueue_head(&dev->mode_config.connector_free_queue);

>  

>  	drm_mode_create_standard_properties(dev);

>  

> @@ -431,8 +432,11 @@ void drm_mode_config_cleanup(struct drm_device *dev)

>  		drm_connector_put(connector);

>  	}

>  	drm_connector_list_iter_end(&conn_iter);

> +

>  	/* connector_iter drops references in a work item. */

> -	flush_scheduled_work();

> +	wait_event(dev->mode_config.connector_free_queue,

> +		   !atomic_read(&dev->mode_config.connector_free_works));

> +

>  	if (WARN_ON(!list_empty(&dev->mode_config.connector_list))) {

>  		drm_connector_list_iter_begin(dev, &conn_iter);

>  		drm_for_each_connector_iter(connector, &conn_iter)

> diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h

> index a0afeb591dcb..83a7db997e83 100644

> --- a/include/drm/drm_mode_config.h

> +++ b/include/drm/drm_mode_config.h

> @@ -413,6 +413,19 @@ struct drm_mode_config {

>  	 * &struct drm_connector_list_iter to walk this list.

>  	 */

>  	struct list_head connector_list;

> +	/**

> +	 * @pending_connector_free_works:

> +	 *

> +	 * Number of scheduled connector->free_work instances, see

> +	 * drm_connector_put_safe().

> +	 */

> +	atomic_t connector_free_works;

> +	/**

> +	 * @pending_connector_free_queue:

> +	 *

> +	 * Wait queue for waiting until connector->free_work is finished.

> +	 */

> +	wait_queue_head_t connector_free_queue;

>  	/**

>  	 * @num_encoder:

>  	 *

> -- 

> 2.15.0

> 

> _______________________________________________

> dri-devel mailing list

> dri-devel@lists.freedesktop.org

> https://lists.freedesktop.org/mailman/listinfo/dri-devel


-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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kbuild test robot Dec. 16, 2017, 4:06 a.m. | #3
Hi Marek,

I love your patch! Perhaps something to improve:

[auto build test WARNING on v4.15-rc3]
[cannot apply to drm/drm-next drm-exynos/exynos-drm/for-next drm-intel/for-linux-next next-20171215]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Marek-Szyprowski/drm-Fix-possible-deadlock-in-drm_mode_config_cleanup/20171216-102239
reproduce: make htmldocs

All warnings (new ones prefixed by >>):

   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   include/net/cfg80211.h:3278: warning: Excess enum value 'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'
   kernel/sched/core.c:5113: warning: No description found for parameter 't'
   kernel/sched/core.c:5113: warning: Excess function parameter 'interval' description in 'sched_rr_get_interval'
   drivers/gpio/gpiolib.c:601: warning: No description found for parameter '16'
   drivers/gpio/gpiolib.c:601: warning: Excess struct member 'events' description in 'lineevent_state'
   include/linux/iio/iio.h:610: warning: No description found for parameter 'iio_dev'
   include/linux/iio/iio.h:610: warning: Excess function parameter 'indio_dev' description in 'iio_device_register'
   include/linux/iio/trigger.h:79: warning: No description found for parameter 'owner'
   fs/inode.c:1680: warning: No description found for parameter 'rcu'
   include/linux/jbd2.h:443: warning: No description found for parameter 'i_transaction'
   include/linux/jbd2.h:443: warning: No description found for parameter 'i_next_transaction'
   include/linux/jbd2.h:443: warning: No description found for parameter 'i_list'
   include/linux/jbd2.h:443: warning: No description found for parameter 'i_vfs_inode'
   include/linux/jbd2.h:443: warning: No description found for parameter 'i_flags'
   include/linux/jbd2.h:497: warning: No description found for parameter 'h_rsv_handle'
   include/linux/jbd2.h:497: warning: No description found for parameter 'h_reserved'
   include/linux/jbd2.h:497: warning: No description found for parameter 'h_type'
   include/linux/jbd2.h:497: warning: No description found for parameter 'h_line_no'
   include/linux/jbd2.h:497: warning: No description found for parameter 'h_start_jiffies'
   include/linux/jbd2.h:497: warning: No description found for parameter 'h_requested_credits'
   include/linux/jbd2.h:497: warning: No description found for parameter 'saved_alloc_context'
   include/linux/jbd2.h:1050: warning: No description found for parameter 'j_chkpt_bhs'
   include/linux/jbd2.h:1050: warning: No description found for parameter 'j_devname'
   include/linux/jbd2.h:1050: warning: No description found for parameter 'j_average_commit_time'
   include/linux/jbd2.h:1050: warning: No description found for parameter 'j_min_batch_time'
   include/linux/jbd2.h:1050: warning: No description found for parameter 'j_max_batch_time'
   include/linux/jbd2.h:1050: warning: No description found for parameter 'j_commit_callback'
   include/linux/jbd2.h:1050: warning: No description found for parameter 'j_failed_commit'
   include/linux/jbd2.h:1050: warning: No description found for parameter 'j_chksum_driver'
   include/linux/jbd2.h:1050: warning: No description found for parameter 'j_csum_seed'
   fs/jbd2/transaction.c:511: warning: No description found for parameter 'type'
   fs/jbd2/transaction.c:511: warning: No description found for parameter 'line_no'
   fs/jbd2/transaction.c:641: warning: No description found for parameter 'gfp_mask'
   include/drm/drm_drv.h:594: warning: No description found for parameter 'gem_prime_pin'
   include/drm/drm_drv.h:594: warning: No description found for parameter 'gem_prime_unpin'
   include/drm/drm_drv.h:594: warning: No description found for parameter 'gem_prime_res_obj'
   include/drm/drm_drv.h:594: warning: No description found for parameter 'gem_prime_get_sg_table'
   include/drm/drm_drv.h:594: warning: No description found for parameter 'gem_prime_import_sg_table'
   include/drm/drm_drv.h:594: warning: No description found for parameter 'gem_prime_vmap'
   include/drm/drm_drv.h:594: warning: No description found for parameter 'gem_prime_vunmap'
   include/drm/drm_drv.h:594: warning: No description found for parameter 'gem_prime_mmap'
   include/drm/drm_mode_config.h:778: warning: No description found for parameter 'connector_free_works'
   include/drm/drm_mode_config.h:778: warning: No description found for parameter 'connector_free_queue'
   include/drm/drm_mode_config.h:778: warning: No description found for parameter 'modifiers_property'
>> include/drm/drm_mode_config.h:778: warning: Excess struct member 'pending_connector_free_works' description in 'drm_mode_config'

>> include/drm/drm_mode_config.h:778: warning: Excess struct member 'pending_connector_free_queue' description in 'drm_mode_config'

   include/drm/drm_mode_config.h:778: warning: Excess struct member 'modifiers' description in 'drm_mode_config'
   include/drm/drm_plane.h:552: warning: No description found for parameter 'modifiers'
   include/drm/drm_plane.h:552: warning: No description found for parameter 'modifier_count'
   drivers/gpu/drm/drm_edid.c:4837: warning: No description found for parameter 'is_hdmi2_sink'
   drivers/gpu/drm/drm_syncobj.c:306: warning: No description found for parameter 'file_private'
   drivers/gpu/drm/drm_syncobj.c:306: warning: No description found for parameter 'syncobj'
   drivers/gpu/drm/drm_syncobj.c:306: warning: No description found for parameter 'handle'
   drivers/gpu/drm/drm_syncobj.c:307: warning: No description found for parameter 'file_private'
   drivers/gpu/drm/drm_syncobj.c:307: warning: No description found for parameter 'syncobj'
   drivers/gpu/drm/drm_syncobj.c:307: warning: No description found for parameter 'handle'
   drivers/gpu/drm/i915/i915_gem.c:548: warning: No description found for parameter 'rps_client'
   drivers/gpu/drm/i915/i915_gem.c:548: warning: Excess function parameter 'rps' description in 'i915_gem_object_wait'
   Error: Cannot open file drivers/gpu/drm/i915/intel_guc_loader.c
   WARNING: kernel-doc 'scripts/kernel-doc -rst -enable-lineno -function GuC-specific firmware loader drivers/gpu/drm/i915/intel_guc_loader.c' failed with return code 1
   Error: Cannot open file drivers/gpu/drm/i915/intel_guc_loader.c
   Error: Cannot open file drivers/gpu/drm/i915/intel_guc_loader.c
   WARNING: kernel-doc 'scripts/kernel-doc -rst -enable-lineno -internal drivers/gpu/drm/i915/intel_guc_loader.c' failed with return code 2
   drivers/gpu/host1x/bus.c:50: warning: No description found for parameter 'driver'
   drivers/gpu/drm/tve200/tve200_drv.c:1: warning: no structured comments found
   net/core/dev.c:1678: warning: Excess function parameter 'dev' description in 'call_netdevice_notifiers_info'
   net/core/dev.c:6361: warning: No description found for parameter 'extack'
   net/core/dev.c:6384: warning: No description found for parameter 'extack'
   include/linux/rcupdate.h:571: ERROR: Unexpected indentation.
   include/linux/rcupdate.h:575: ERROR: Unexpected indentation.
   include/linux/rcupdate.h:579: WARNING: Block quote ends without a blank line; unexpected unindent.
   include/linux/rcupdate.h:581: WARNING: Block quote ends without a blank line; unexpected unindent.
   include/linux/rcupdate.h:581: WARNING: Inline literal start-string without end-string.
   kernel/time/timer.c:1253: ERROR: Unexpected indentation.
   kernel/time/timer.c:1255: ERROR: Unexpected indentation.
   kernel/time/timer.c:1256: WARNING: Block quote ends without a blank line; unexpected unindent.
   include/linux/wait.h:110: WARNING: Block quote ends without a blank line; unexpected unindent.
   include/linux/wait.h:113: ERROR: Unexpected indentation.
   include/linux/wait.h:115: WARNING: Block quote ends without a blank line; unexpected unindent.
   kernel/time/hrtimer.c:989: WARNING: Block quote ends without a blank line; unexpected unindent.
   kernel/signal.c:325: WARNING: Inline literal start-string without end-string.
   include/linux/iio/iio.h:219: ERROR: Unexpected indentation.
   include/linux/iio/iio.h:220: WARNING: Block quote ends without a blank line; unexpected unindent.
   include/linux/iio/iio.h:226: WARNING: Definition list ends without a blank line; unexpected unindent.
   drivers/ata/libata-core.c:5913: ERROR: Unknown target name: "hw".
   drivers/message/fusion/mptbase.c:5051: WARNING: Definition list ends without a blank line; unexpected unindent.
   drivers/tty/serial/serial_core.c:1899: WARNING: Definition list ends without a blank line; unexpected unindent.
   include/linux/regulator/driver.h:271: ERROR: Unknown target name: "regulator_regmap_x_voltage".
   include/linux/spi/spi.h:373: ERROR: Unexpected indentation.
   drivers/w1/w1_io.c:197: WARNING: Definition list ends without a blank line; unexpected unindent.
   net/core/dev.c:4483: ERROR: Unknown target name: "page_is".
   Documentation/trace/ftrace-uses.rst:53: WARNING: Definition list ends without a blank line; unexpected unindent.
   Documentation/trace/ftrace-uses.rst:89: WARNING: Inline emphasis start-string without end-string.
   Documentation/trace/ftrace-uses.rst:89: WARNING: Inline emphasis start-string without end-string.
   Documentation/errseq.rst:: WARNING: document isn't included in any toctree
   Documentation/networking/msg_zerocopy.rst:: WARNING: document isn't included in any toctree
   Documentation/trace/ftrace-uses.rst:: WARNING: document isn't included in any toctree
   Documentation/virtual/kvm/vcpu-requests.rst:: WARNING: document isn't included in any toctree
   Documentation/dev-tools/kselftest.rst:15: WARNING: Could not lex literal_block as "c". Highlighting skipped.
   Fontconfig warning: "/home/kbuild/.config/fontconfig/fonts.conf", line 43: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "/home/kbuild/.config/fontconfig/fonts.conf", line 56: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "/home/kbuild/.config/fontconfig/fonts.conf", line 69: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "/home/kbuild/.config/fontconfig/fonts.conf", line 82: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "/home/kbuild/.config/fontconfig/fonts.conf", line 96: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "/home/kbuild/.config/fontconfig/fonts.conf", line 109: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "/home/kbuild/.config/fontconfig/fonts.conf", line 122: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "/home/kbuild/.config/fontconfig/fonts.conf", line 133: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "/home/kbuild/.config/fontconfig/fonts.conf", line 164: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "/home/kbuild/.config/fontconfig/fonts.conf", line 193: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "~/.fonts.conf", line 43: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "~/.fonts.conf", line 56: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "~/.fonts.conf", line 69: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "~/.fonts.conf", line 82: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "~/.fonts.conf", line 96: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "~/.fonts.conf", line 109: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "~/.fonts.conf", line 122: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "~/.fonts.conf", line 133: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "~/.fonts.conf", line 164: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "~/.fonts.conf", line 193: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "/home/kbuild/.config/fontconfig/fonts.conf", line 43: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "/home/kbuild/.config/fontconfig/fonts.conf", line 56: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "/home/kbuild/.config/fontconfig/fonts.conf", line 69: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "/home/kbuild/.config/fontconfig/fonts.conf", line 82: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "/home/kbuild/.config/fontconfig/fonts.conf", line 96: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "/home/kbuild/.config/fontconfig/fonts.conf", line 109: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "/home/kbuild/.config/fontconfig/fonts.conf", line 122: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "/home/kbuild/.config/fontconfig/fonts.conf", line 133: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "/home/kbuild/.config/fontconfig/fonts.conf", line 164: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "/home/kbuild/.config/fontconfig/fonts.conf", line 193: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "~/.fonts.conf", line 43: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "~/.fonts.conf", line 56: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "~/.fonts.conf", line 69: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "~/.fonts.conf", line 82: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "~/.fonts.conf", line 96: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "~/.fonts.conf", line 109: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "~/.fonts.conf", line 122: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "~/.fonts.conf", line 133: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "~/.fonts.conf", line 164: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "~/.fonts.conf", line 193: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "/home/kbuild/.config/fontconfig/fonts.conf", line 43: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "/home/kbuild/.config/fontconfig/fonts.conf", line 56: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "/home/kbuild/.config/fontconfig/fonts.conf", line 69: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "/home/kbuild/.config/fontconfig/fonts.conf", line 82: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "/home/kbuild/.config/fontconfig/fonts.conf", line 96: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "/home/kbuild/.config/fontconfig/fonts.conf", line 109: Having multiple values in <test> isn't supported and may not work as expected
   Fontconfig warning: "/home/kbuild/.config/fontconfig/fonts.conf", line 122: Having multiple values in <test> isn't supported and may not work as expected

vim +778 include/drm/drm_mode_config.h

28575f16 Daniel Vetter 2016-11-14 @778  

:::::: The code at line 778 was first introduced by commit
:::::: 28575f165d36051310d7ea2350e2011f8095b6fb drm: Extract drm_mode_config.[hc]

:::::: TO: Daniel Vetter <daniel.vetter@ffwll.ch>
:::::: CC: Daniel Vetter <daniel.vetter@ffwll.ch>

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

Patch

diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
index 0b7e0974e6da..7620ac1ad1b1 100644
--- a/drivers/gpu/drm/drm_connector.c
+++ b/drivers/gpu/drm/drm_connector.c
@@ -161,6 +161,8 @@  static void drm_connector_free_work_fn(struct work_struct *work)
 
 	drm_mode_object_unregister(dev, &connector->base);
 	connector->funcs->destroy(connector);
+	atomic_dec(&dev->mode_config.connector_free_works);
+	wake_up_all(&dev->mode_config.connector_free_queue);
 }
 
 /**
@@ -552,8 +554,10 @@  EXPORT_SYMBOL(drm_connector_list_iter_begin);
 static void
 drm_connector_put_safe(struct drm_connector *conn)
 {
-	if (refcount_dec_and_test(&conn->base.refcount.refcount))
+	if (refcount_dec_and_test(&conn->base.refcount.refcount)) {
+		atomic_inc(&conn->dev->mode_config.connector_free_works);
 		schedule_work(&conn->free_work);
+	}
 }
 
 /**
diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c
index 6ffe952142e6..cca443faebd8 100644
--- a/drivers/gpu/drm/drm_mode_config.c
+++ b/drivers/gpu/drm/drm_mode_config.c
@@ -381,6 +381,7 @@  void drm_mode_config_init(struct drm_device *dev)
 	idr_init(&dev->mode_config.tile_idr);
 	ida_init(&dev->mode_config.connector_ida);
 	spin_lock_init(&dev->mode_config.connector_list_lock);
+	init_waitqueue_head(&dev->mode_config.connector_free_queue);
 
 	drm_mode_create_standard_properties(dev);
 
@@ -431,8 +432,11 @@  void drm_mode_config_cleanup(struct drm_device *dev)
 		drm_connector_put(connector);
 	}
 	drm_connector_list_iter_end(&conn_iter);
+
 	/* connector_iter drops references in a work item. */
-	flush_scheduled_work();
+	wait_event(dev->mode_config.connector_free_queue,
+		   !atomic_read(&dev->mode_config.connector_free_works));
+
 	if (WARN_ON(!list_empty(&dev->mode_config.connector_list))) {
 		drm_connector_list_iter_begin(dev, &conn_iter);
 		drm_for_each_connector_iter(connector, &conn_iter)
diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
index a0afeb591dcb..83a7db997e83 100644
--- a/include/drm/drm_mode_config.h
+++ b/include/drm/drm_mode_config.h
@@ -413,6 +413,19 @@  struct drm_mode_config {
 	 * &struct drm_connector_list_iter to walk this list.
 	 */
 	struct list_head connector_list;
+	/**
+	 * @pending_connector_free_works:
+	 *
+	 * Number of scheduled connector->free_work instances, see
+	 * drm_connector_put_safe().
+	 */
+	atomic_t connector_free_works;
+	/**
+	 * @pending_connector_free_queue:
+	 *
+	 * Wait queue for waiting until connector->free_work is finished.
+	 */
+	wait_queue_head_t connector_free_queue;
 	/**
 	 * @num_encoder:
 	 *