Re: [PATCH v10 01/16] videobuf2: Make struct vb2_buffer refcounted

[sathyam panda]

Hi Ezequiel,

On 5/29/18, Ezequiel Garcia  wrote:
> On Fri, 2018-05-25 at 12:11 +0530, sathyam panda wrote:
>> Hello,
>>
>> On 5/21/18, Ezequiel Garcia  wrote:
>> > The in-fence implementation involves having a per-buffer fence
>> > callback,
>> > that triggers on the fence signal. The fence callback is called
>> > asynchronously
>> > and needs a valid reference to the associated ideobuf2 buffer.
>> >
>> > Allow this by making the vb2_buffer refcounted, so it can be passed
>> > to other contexts.
>> >
>>
>> -Is it really required, because when a queued buffer with an in_fence
>> is deallocated, firstly queue is cancelled.
>> -And __vb2_dqbuf is called which calls dma_fence_remove_callback.
>> -So if fence callback has been called -__vb2_dqbuf will wait to
>> acquire fence lock.
>> -So during execution of fence callback, buffers and queue are still
>> valid.
>> -And if __vb2_dqbuf remove callback first ,then dma_fence_signal will
>> wait for lock
>> - so there won't be any fence callback to call for that buffer when
>> dma_fence_signal resumes.
>>
>
> Hi Sathyam,
>
> Thanks for your review! The refcount is definitely required,
> as the fence callback only schedules a workqueue, which is
> completely asynchronous with respect to the rest of the
> ioctls.
>
> In particular, the workqueue is not synchronized with
> vb2_core_queue_release.
>
> Also, another subtle detail, dma_fence_remove_callback
> can fail to remove the callback.
>
> Thanks,
> Eze
>

- Sorry, I didn't pay attention to the use of workqueue, thanks for
bringing that into my notice. Now it make sense.
- I have a doubt about the queue since many driver specific structures
have queues which they release with kfree() after calling
vb2_queue_release().
- And since vb2_core_queue_release decrements the buffer refcount only
once if fence is already signalled, so buffer is still valid, but
queue isn't as the memory is deallocated.
- So is it safe to access queue in the __qbuf_work. Please correct me
if I am wrong.

Regards,
Sathyam

Re: [PATCH v10 01/16] videobuf2: Make struct vb2_buffer refcounted

[sathyam panda]

Hi Ezequiel,

On 5/29/18, Ezequiel Garcia  wrote:
> On Fri, 2018-05-25 at 12:11 +0530, sathyam panda wrote:
>> Hello,
>>
>> On 5/21/18, Ezequiel Garcia  wrote:
>> > The in-fence implementation involves having a per-buffer fence
>> > callback,
>> > that triggers on the fence signal. The fence callback is called
>> > asynchronously
>> > and needs a valid reference to the associated ideobuf2 buffer.
>> >
>> > Allow this by making the vb2_buffer refcounted, so it can be passed
>> > to other contexts.
>> >
>>
>> -Is it really required, because when a queued buffer with an in_fence
>> is deallocated, firstly queue is cancelled.
>> -And __vb2_dqbuf is called which calls dma_fence_remove_callback.
>> -So if fence callback has been called -__vb2_dqbuf will wait to
>> acquire fence lock.
>> -So during execution of fence callback, buffers and queue are still
>> valid.
>> -And if __vb2_dqbuf remove callback first ,then dma_fence_signal will
>> wait for lock
>> - so there won't be any fence callback to call for that buffer when
>> dma_fence_signal resumes.
>>
>
> Hi Sathyam,
>
> Thanks for your review! The refcount is definitely required,
> as the fence callback only schedules a workqueue, which is
> completely asynchronous with respect to the rest of the
> ioctls.
>
> In particular, the workqueue is not synchronized with
> vb2_core_queue_release.
>
> Also, another subtle detail, dma_fence_remove_callback
> can fail to remove the callback.
>
> Thanks,
> Eze
>

- Sorry, I didn't pay attention to the use of workqueue, thanks for
bringing that into my notice. Now it make sense.
- I have a doubt about the queue since many driver specific structures
have queues which they release with kfree() after calling
vb2_queue_release().
- And since vb2_core_queue_release decrements the buffer refcount only
once if fence is already signalled, so buffer is still valid, but
queue isn't as the memory is deallocated.
- So is it safe to access queue in the __qbuf_work. Please correct me
if I am wrong.

Regards,
Sathyam

Re: [PATCH v10 01/16] videobuf2: Make struct vb2_buffer refcounted

[sathyam panda]

Hello,

On 5/21/18, Ezequiel Garcia  wrote:
> The in-fence implementation involves having a per-buffer fence callback,
> that triggers on the fence signal. The fence callback is called
> asynchronously
> and needs a valid reference to the associated ideobuf2 buffer.
>
> Allow this by making the vb2_buffer refcounted, so it can be passed
> to other contexts.
>

-Is it really required, because when a queued buffer with an in_fence
is deallocated, firstly queue is cancelled.
-And __vb2_dqbuf is called which calls dma_fence_remove_callback.
-So if fence callback has been called -__vb2_dqbuf will wait to
acquire fence lock.
-So during execution of fence callback, buffers and queue are still valid.
-And if __vb2_dqbuf remove callback first ,then dma_fence_signal will
wait for lock
- so there won't be any fence callback to call for that buffer when
dma_fence_signal resumes.

> Signed-off-by: Ezequiel Garcia 
> ---
>  drivers/media/common/videobuf2/videobuf2-core.c | 27
> ++---
>  include/media/videobuf2-core.h  |  7 +--
>  2 files changed, 29 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c
> b/drivers/media/common/videobuf2/videobuf2-core.c
> index d3f7bb33a54d..f1feb45c1e37 100644
> --- a/drivers/media/common/videobuf2/videobuf2-core.c
> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
> @@ -190,6 +190,26 @@ module_param(debug, int, 0644);
>  static void __vb2_queue_cancel(struct vb2_queue *q);
>  static void __enqueue_in_driver(struct vb2_buffer *vb);
>
> +static void __vb2_buffer_free(struct kref *kref)
> +{
> + struct vb2_buffer *vb =
> + container_of(kref, struct vb2_buffer, refcount);
> + kfree(vb);
> +}
> +
> +static void __vb2_buffer_put(struct vb2_buffer *vb)
> +{
> + if (vb)
> + kref_put(>refcount, __vb2_buffer_free);
> +}
> +
> +static struct vb2_buffer *__vb2_buffer_get(struct vb2_buffer *vb)
> +{
> + if (vb)
> + kref_get(>refcount);
> + return vb;
> +}
> +
>  /*
>   * __vb2_buf_mem_alloc() - allocate video memory for the given buffer
>   */
> @@ -346,6 +366,7 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum
> vb2_memory memory,
>   break;
>   }
>
> + kref_init(>refcount);
>   vb->state = VB2_BUF_STATE_DEQUEUED;
>   vb->vb2_queue = q;
>   vb->num_planes = num_planes;
> @@ -365,7 +386,7 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum
> vb2_memory memory,
>   dprintk(1, "failed allocating memory for buffer 
> %d\n",
>   buffer);
>   q->bufs[vb->index] = NULL;
> - kfree(vb);
> + __vb2_buffer_put(vb);
>   break;
>   }
>   __setup_offsets(vb);
> @@ -380,7 +401,7 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum
> vb2_memory memory,
>   buffer, vb);
>   __vb2_buf_mem_free(vb);
>   q->bufs[vb->index] = NULL;
> - kfree(vb);
> + __vb2_buffer_put(vb);
>   break;
>   }
>   }
> @@ -520,7 +541,7 @@ static int __vb2_queue_free(struct vb2_queue *q,
> unsigned int buffers)
>   /* Free videobuf buffers */
>   for (buffer = q->num_buffers - buffers; buffer < q->num_buffers;
>++buffer) {
> - kfree(q->bufs[buffer]);
> + __vb2_buffer_put(q->bufs[buffer]);
>   q->bufs[buffer] = NULL;
>   }
>
> diff --git a/include/media/videobuf2-core.h
> b/include/media/videobuf2-core.h
> index f6818f732f34..baa4632c7e59 100644
> --- a/include/media/videobuf2-core.h
> +++ b/include/media/videobuf2-core.h
> @@ -12,11 +12,12 @@
>  #ifndef _MEDIA_VIDEOBUF2_CORE_H
>  #define _MEDIA_VIDEOBUF2_CORE_H
>
> +#include 
> +#include 
> +#include 
>  #include 
>  #include 
>  #include 
> -#include 
> -#include 
>
>  #define VB2_MAX_FRAME(32)
>  #define VB2_MAX_PLANES   (8)
> @@ -249,6 +250,7 @@ struct vb2_buffer {
>
>   /* private: internal use only
>*
> +  * refcount:refcount for this buffer
>* state:   current buffer state; do not change
>* queued_entry:entry on the queued buffers list, which holds
>*  all buffers queued from userspace
> @@ -256,6 +258,7 @@ struct vb2_buffer {
>*  to be dequeued to userspace
>* vb2_plane:   per-plane information; do not change
>*/
> + struct kref refcount;
>   enum vb2_buffer_state   state;
>
>   struct vb2_planeplanes[VB2_MAX_PLANES];
>

Regards,
 Sathyam

Re: [PATCH v10 01/16] videobuf2: Make struct vb2_buffer refcounted

[sathyam panda]

Hello,

On 5/21/18, Ezequiel Garcia  wrote:
> The in-fence implementation involves having a per-buffer fence callback,
> that triggers on the fence signal. The fence callback is called
> asynchronously
> and needs a valid reference to the associated ideobuf2 buffer.
>
> Allow this by making the vb2_buffer refcounted, so it can be passed
> to other contexts.
>

-Is it really required, because when a queued buffer with an in_fence
is deallocated, firstly queue is cancelled.
-And __vb2_dqbuf is called which calls dma_fence_remove_callback.
-So if fence callback has been called -__vb2_dqbuf will wait to
acquire fence lock.
-So during execution of fence callback, buffers and queue are still valid.
-And if __vb2_dqbuf remove callback first ,then dma_fence_signal will
wait for lock
- so there won't be any fence callback to call for that buffer when
dma_fence_signal resumes.

> Signed-off-by: Ezequiel Garcia 
> ---
>  drivers/media/common/videobuf2/videobuf2-core.c | 27
> ++---
>  include/media/videobuf2-core.h  |  7 +--
>  2 files changed, 29 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c
> b/drivers/media/common/videobuf2/videobuf2-core.c
> index d3f7bb33a54d..f1feb45c1e37 100644
> --- a/drivers/media/common/videobuf2/videobuf2-core.c
> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
> @@ -190,6 +190,26 @@ module_param(debug, int, 0644);
>  static void __vb2_queue_cancel(struct vb2_queue *q);
>  static void __enqueue_in_driver(struct vb2_buffer *vb);
>
> +static void __vb2_buffer_free(struct kref *kref)
> +{
> + struct vb2_buffer *vb =
> + container_of(kref, struct vb2_buffer, refcount);
> + kfree(vb);
> +}
> +
> +static void __vb2_buffer_put(struct vb2_buffer *vb)
> +{
> + if (vb)
> + kref_put(>refcount, __vb2_buffer_free);
> +}
> +
> +static struct vb2_buffer *__vb2_buffer_get(struct vb2_buffer *vb)
> +{
> + if (vb)
> + kref_get(>refcount);
> + return vb;
> +}
> +
>  /*
>   * __vb2_buf_mem_alloc() - allocate video memory for the given buffer
>   */
> @@ -346,6 +366,7 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum
> vb2_memory memory,
>   break;
>   }
>
> + kref_init(>refcount);
>   vb->state = VB2_BUF_STATE_DEQUEUED;
>   vb->vb2_queue = q;
>   vb->num_planes = num_planes;
> @@ -365,7 +386,7 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum
> vb2_memory memory,
>   dprintk(1, "failed allocating memory for buffer 
> %d\n",
>   buffer);
>   q->bufs[vb->index] = NULL;
> - kfree(vb);
> + __vb2_buffer_put(vb);
>   break;
>   }
>   __setup_offsets(vb);
> @@ -380,7 +401,7 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum
> vb2_memory memory,
>   buffer, vb);
>   __vb2_buf_mem_free(vb);
>   q->bufs[vb->index] = NULL;
> - kfree(vb);
> + __vb2_buffer_put(vb);
>   break;
>   }
>   }
> @@ -520,7 +541,7 @@ static int __vb2_queue_free(struct vb2_queue *q,
> unsigned int buffers)
>   /* Free videobuf buffers */
>   for (buffer = q->num_buffers - buffers; buffer < q->num_buffers;
>++buffer) {
> - kfree(q->bufs[buffer]);
> + __vb2_buffer_put(q->bufs[buffer]);
>   q->bufs[buffer] = NULL;
>   }
>
> diff --git a/include/media/videobuf2-core.h
> b/include/media/videobuf2-core.h
> index f6818f732f34..baa4632c7e59 100644
> --- a/include/media/videobuf2-core.h
> +++ b/include/media/videobuf2-core.h
> @@ -12,11 +12,12 @@
>  #ifndef _MEDIA_VIDEOBUF2_CORE_H
>  #define _MEDIA_VIDEOBUF2_CORE_H
>
> +#include 
> +#include 
> +#include 
>  #include 
>  #include 
>  #include 
> -#include 
> -#include 
>
>  #define VB2_MAX_FRAME(32)
>  #define VB2_MAX_PLANES   (8)
> @@ -249,6 +250,7 @@ struct vb2_buffer {
>
>   /* private: internal use only
>*
> +  * refcount:refcount for this buffer
>* state:   current buffer state; do not change
>* queued_entry:entry on the queued buffers list, which holds
>*  all buffers queued from userspace
> @@ -256,6 +258,7 @@ struct vb2_buffer {
>*  to be dequeued to userspace
>* vb2_plane:   per-plane information; do not change
>*/
> + struct kref refcount;
>   enum vb2_buffer_state   state;
>
>   struct vb2_planeplanes[VB2_MAX_PLANES];
>

Regards,
 Sathyam

Re: [PATCH v10 12/16] vb2: add in-fence support to QBUF

[sathyam panda]

Hello,

On 5/21/18, Ezequiel Garcia  wrote:
> From: Gustavo Padovan 
>
> Receive in-fence from userspace and add support for waiting on them
> before queueing the buffer to the driver. Buffers can't be queued to the
> driver before its fences signal. And a buffer can't be queued to the driver
> out of the order they were queued from userspace. That means that even if
> its fence signals it must wait for all other buffers, ahead of it in the
> queue,
> to signal first.
>
> If the fence for some buffer fails we do not queue it to the driver,
> instead we mark it as error and wait until the previous buffer is done
> to notify userspace of the error. We wait here to deliver the buffers back
> to userspace in order.
>
> v13: - cleanup implementation.
>  - remove wrong Kconfig changes.
>  - print noisy warning on unexpected enqueue conditioin
>  - schedule a vb2_start_streaming work from the fence callback
>
> v12: fixed dvb_vb2.c usage of vb2_core_qbuf.
>
> v11: - minor doc/comments fixes (Hans Verkuil)
>  - reviewed the in-fence path at __fill_v4l2_buffer()
>
> v10: - rename fence to in_fence in many places
>  - handle fences signalling with error better (Hans Verkuil)
>
> v9: - improve comments and docs (Hans Verkuil)
> - fix unlocking of vb->fence_cb_lock on vb2_core_qbuf (Hans Verkuil)
> - move in-fences code that was in the out-fences patch here (Alex)
>
> v8: - improve comments about fences with errors
>
> v7: - get rid of the fence array stuff for ordering and just use
>   get_num_buffers_ready() (Hans)
> - fix issue of queuing the buffer twice (Hans)
> - avoid the dma_fence_wait() in core_qbuf() (Alex)
> - merge preparation commit in
>
> v6: - With fences always keep the order userspace queues the buffers.
> - Protect in_fence manipulation with a lock (Brian Starkey)
> - check if fences have the same context before adding a fence array
> - Fix last_fence ref unbalance in __set_in_fence() (Brian Starkey)
> - Clean up fence if __set_in_fence() fails (Brian Starkey)
> - treat -EINVAL from dma_fence_add_callback() (Brian Starkey)
>
> v5: - use fence_array to keep buffers ordered in vb2 core when
>   needed (Brian Starkey)
> - keep backward compat on the reserved2 field (Brian Starkey)
> - protect fence callback removal with lock (Brian Starkey)
>
> v4: - Add a comment about dma_fence_add_callback() not returning a
>   error (Hans)
> - Call dma_fence_put(vb->in_fence) if fence signaled (Hans)
> - select SYNC_FILE under config VIDEOBUF2_CORE (Hans)
> - Move dma_fence_is_signaled() check to __enqueue_in_driver() (Hans)
> - Remove list_for_each_entry() in __vb2_core_qbuf() (Hans)
> - Remove if (vb->state != VB2_BUF_STATE_QUEUED) from
>   vb2_start_streaming() (Hans)
> - set IN_FENCE flags on __fill_v4l2_buffer (Hans)
> - Queue buffers to the driver as soon as they are ready (Hans)
> - call fill_user_buffer() after queuing the buffer (Hans)
> - add err: label to clean up fence
> - add dma_fence_wait() before calling vb2_start_streaming()
>
> v3: - document fence parameter
> - remove ternary if at vb2_qbuf() return (Mauro)
> - do not change if conditions behaviour (Mauro)
>
> v2: - fix vb2_queue_or_prepare_buf() ret check
> - remove check for VB2_MEMORY_DMABUF only (Javier)
> - check num of ready buffers to start streaming
> - when queueing, start from the first ready buffer
> - handle queue cancel
>
> Signed-off-by: Gustavo Padovan 
> Signed-off-by: Ezequiel Garcia 
> ---
>  drivers/media/common/videobuf2/Kconfig  |   1 +
>  drivers/media/common/videobuf2/videobuf2-core.c | 224
> 
>  drivers/media/common/videobuf2/videobuf2-v4l2.c |  37 +++-
>  drivers/media/dvb-core/dvb_vb2.c|   2 +-
>  include/media/videobuf2-core.h  |  19 +-
>  5 files changed, 242 insertions(+), 41 deletions(-)
>
> diff --git a/drivers/media/common/videobuf2/Kconfig
> b/drivers/media/common/videobuf2/Kconfig
> index 17c32ea58395..27ad9e8a268b 100644
> --- a/drivers/media/common/videobuf2/Kconfig
> +++ b/drivers/media/common/videobuf2/Kconfig
> @@ -1,6 +1,7 @@
>  # Used by drivers that need Videobuf2 modules
>  config VIDEOBUF2_CORE
>   select DMA_SHARED_BUFFER
> + select SYNC_FILE
>   tristate
>
>  config VIDEOBUF2_V4L2
> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c
> b/drivers/media/common/videobuf2/videobuf2-core.c
> index a9a0a9d1decb..86b5ebe25263 100644
> --- a/drivers/media/common/videobuf2/videobuf2-core.c
> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
> @@ -27,6 +27,7 @@
>  #include 
>
>  #include 
> +#include 
>  #include 
>
>  #include 
> @@ -189,6 +190,7 @@ module_param(debug, int, 0644);
>
>  static void __vb2_queue_cancel(struct vb2_queue *q);
>  static void 

Re: [PATCH v10 12/16] vb2: add in-fence support to QBUF

[sathyam panda]

Hello,

On 5/21/18, Ezequiel Garcia  wrote:
> From: Gustavo Padovan 
>
> Receive in-fence from userspace and add support for waiting on them
> before queueing the buffer to the driver. Buffers can't be queued to the
> driver before its fences signal. And a buffer can't be queued to the driver
> out of the order they were queued from userspace. That means that even if
> its fence signals it must wait for all other buffers, ahead of it in the
> queue,
> to signal first.
>
> If the fence for some buffer fails we do not queue it to the driver,
> instead we mark it as error and wait until the previous buffer is done
> to notify userspace of the error. We wait here to deliver the buffers back
> to userspace in order.
>
> v13: - cleanup implementation.
>  - remove wrong Kconfig changes.
>  - print noisy warning on unexpected enqueue conditioin
>  - schedule a vb2_start_streaming work from the fence callback
>
> v12: fixed dvb_vb2.c usage of vb2_core_qbuf.
>
> v11: - minor doc/comments fixes (Hans Verkuil)
>  - reviewed the in-fence path at __fill_v4l2_buffer()
>
> v10: - rename fence to in_fence in many places
>  - handle fences signalling with error better (Hans Verkuil)
>
> v9: - improve comments and docs (Hans Verkuil)
> - fix unlocking of vb->fence_cb_lock on vb2_core_qbuf (Hans Verkuil)
> - move in-fences code that was in the out-fences patch here (Alex)
>
> v8: - improve comments about fences with errors
>
> v7: - get rid of the fence array stuff for ordering and just use
>   get_num_buffers_ready() (Hans)
> - fix issue of queuing the buffer twice (Hans)
> - avoid the dma_fence_wait() in core_qbuf() (Alex)
> - merge preparation commit in
>
> v6: - With fences always keep the order userspace queues the buffers.
> - Protect in_fence manipulation with a lock (Brian Starkey)
> - check if fences have the same context before adding a fence array
> - Fix last_fence ref unbalance in __set_in_fence() (Brian Starkey)
> - Clean up fence if __set_in_fence() fails (Brian Starkey)
> - treat -EINVAL from dma_fence_add_callback() (Brian Starkey)
>
> v5: - use fence_array to keep buffers ordered in vb2 core when
>   needed (Brian Starkey)
> - keep backward compat on the reserved2 field (Brian Starkey)
> - protect fence callback removal with lock (Brian Starkey)
>
> v4: - Add a comment about dma_fence_add_callback() not returning a
>   error (Hans)
> - Call dma_fence_put(vb->in_fence) if fence signaled (Hans)
> - select SYNC_FILE under config VIDEOBUF2_CORE (Hans)
> - Move dma_fence_is_signaled() check to __enqueue_in_driver() (Hans)
> - Remove list_for_each_entry() in __vb2_core_qbuf() (Hans)
> - Remove if (vb->state != VB2_BUF_STATE_QUEUED) from
>   vb2_start_streaming() (Hans)
> - set IN_FENCE flags on __fill_v4l2_buffer (Hans)
> - Queue buffers to the driver as soon as they are ready (Hans)
> - call fill_user_buffer() after queuing the buffer (Hans)
> - add err: label to clean up fence
> - add dma_fence_wait() before calling vb2_start_streaming()
>
> v3: - document fence parameter
> - remove ternary if at vb2_qbuf() return (Mauro)
> - do not change if conditions behaviour (Mauro)
>
> v2: - fix vb2_queue_or_prepare_buf() ret check
> - remove check for VB2_MEMORY_DMABUF only (Javier)
> - check num of ready buffers to start streaming
> - when queueing, start from the first ready buffer
> - handle queue cancel
>
> Signed-off-by: Gustavo Padovan 
> Signed-off-by: Ezequiel Garcia 
> ---
>  drivers/media/common/videobuf2/Kconfig  |   1 +
>  drivers/media/common/videobuf2/videobuf2-core.c | 224
> 
>  drivers/media/common/videobuf2/videobuf2-v4l2.c |  37 +++-
>  drivers/media/dvb-core/dvb_vb2.c|   2 +-
>  include/media/videobuf2-core.h  |  19 +-
>  5 files changed, 242 insertions(+), 41 deletions(-)
>
> diff --git a/drivers/media/common/videobuf2/Kconfig
> b/drivers/media/common/videobuf2/Kconfig
> index 17c32ea58395..27ad9e8a268b 100644
> --- a/drivers/media/common/videobuf2/Kconfig
> +++ b/drivers/media/common/videobuf2/Kconfig
> @@ -1,6 +1,7 @@
>  # Used by drivers that need Videobuf2 modules
>  config VIDEOBUF2_CORE
>   select DMA_SHARED_BUFFER
> + select SYNC_FILE
>   tristate
>
>  config VIDEOBUF2_V4L2
> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c
> b/drivers/media/common/videobuf2/videobuf2-core.c
> index a9a0a9d1decb..86b5ebe25263 100644
> --- a/drivers/media/common/videobuf2/videobuf2-core.c
> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
> @@ -27,6 +27,7 @@
>  #include 
>
>  #include 
> +#include 
>  #include 
>
>  #include 
> @@ -189,6 +190,7 @@ module_param(debug, int, 0644);
>
>  static void __vb2_queue_cancel(struct vb2_queue *q);
>  static void __enqueue_in_driver(struct vb2_buffer *vb);
> +static void __qbuf_work(struct work_struct *work);
>
>  static void