Re: [PATCH v14 43/56] media: videobuf2: Be more flexible on the number of queue stored buffers

From: Hans Verkuil
Date: Thu Nov 02 2023 - 04:17:54 EST

Hi Benjamin,

After a lot of testing yesterday I discovered that this patch introduces a
bug. After this bug, running the test-media script will result in a lot of
unbalanced counters messages:

[Wed Nov 1 16:40:48 2023] videobuf2_common: unbalanced counters for queue ffff888115a07f00, buffer 11:
[Wed Nov 1 16:40:48 2023] videobuf2_common: buf_init: 1 buf_cleanup: 0
[Wed Nov 1 16:40:48 2023] videobuf2_common: alloc: 1 put: 0
[Wed Nov 1 16:40:48 2023] videobuf2_common: get_dmabuf: 0 num_users: 0

Apparently buf_init is called, but not buf_cleanup.

I also get loads of kmemleak reports:

unreferenced object 0xffff88800eae6800 (size 2048):
comm "v4l2-compliance", pid 652, jiffies 4294937190 (age 149.650s)
hex dump (first 32 bytes):
e0 52 18 0c 81 88 ff ff 00 00 00 00 02 00 00 00 .R..............
01 00 00 00 01 00 00 00 20 2f d3 f3 3e 00 00 00 ........ /..>...
backtrace:
[<ffffffffacbdb08b>] __kmalloc+0x4b/0x150
[<ffffffffc01df77a>] __vb2_queue_alloc+0x11a/0xca0 [videobuf2_common]
[<ffffffffc01e74f5>] vb2_core_reqbufs+0x735/0xfd0 [videobuf2_common]
[<ffffffffc046ca71>] v4l2_m2m_ioctl_reqbufs+0xc1/0x1b0 [v4l2_mem2mem]
[<ffffffffc0231520>] __video_do_ioctl+0x8d0/0xc20 [videodev]
[<ffffffffc0232bcc>] video_usercopy+0x48c/0xd00 [videodev]
[<ffffffffc021e2ff>] v4l2_ioctl+0x17f/0x1f0 [videodev]
[<ffffffffacd758ce>] __do_compat_sys_ioctl+0x13e/0x1d0
[<ffffffffae7df992>] __do_fast_syscall_32+0x62/0xe0
[<ffffffffae7dfb4f>] do_fast_syscall_32+0x2f/0x70
[<ffffffffaea012ed>] entry_SYSCALL_compat_after_hwframe+0x45/0x4d

Very likely the same issue.

Unfortunately, the build script does not yet check for issues like this,
you have to manually inspect the test-media logs (found in the logs directory
after the run). It's on my TODO list.

Regards,

Hans

On 31/10/2023 17:30, Benjamin Gaignard wrote:
> Add 'max_num_buffers' field in vb2_queue struct to let drivers decide
> how many buffers could be stored in a queue.
> This require 'bufs' array to be allocated at queue init time and freed
> when releasing the queue.
> By default VB2_MAX_FRAME remains the limit.
>
> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxxxxx>
> Signed-off-by: Hans Verkuil <hverkuil-cisco@xxxxxxxxx>
> ---
> .../media/common/videobuf2/videobuf2-core.c | 41 +++++++++++++++----
> .../media/common/videobuf2/videobuf2-v4l2.c | 6 +--
> include/media/videobuf2-core.h | 10 ++++-
> 3 files changed, 44 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
> index c5c5ae4d213d..72ef7179d80a 100644
> --- a/drivers/media/common/videobuf2/videobuf2-core.c
> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
> @@ -416,7 +416,7 @@ static void init_buffer_cache_hints(struct vb2_queue *q, struct vb2_buffer *vb)
> */
> static void vb2_queue_add_buffer(struct vb2_queue *q, struct vb2_buffer *vb, unsigned int index)
> {
> - WARN_ON(index >= VB2_MAX_FRAME || q->bufs[index]);
> + WARN_ON(index >= q->max_num_buffers || q->bufs[index]);
>
> q->bufs[index] = vb;
> vb->index = index;
> @@ -449,9 +449,9 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum vb2_memory memory,
> struct vb2_buffer *vb;
> int ret;
>
> - /* Ensure that q->num_buffers+num_buffers is below VB2_MAX_FRAME */
> + /* Ensure that the number of already queue + num_buffers is below q->max_num_buffers */
> num_buffers = min_t(unsigned int, num_buffers,
> - VB2_MAX_FRAME - q_num_buffers);
> + q->max_num_buffers - q_num_buffers);
>
> for (buffer = 0; buffer < num_buffers; ++buffer) {
> /* Allocate vb2 buffer structures */
> @@ -813,7 +813,7 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
> unsigned plane_sizes[VB2_MAX_PLANES] = { };
> bool non_coherent_mem = flags & V4L2_MEMORY_FLAG_NON_COHERENT;
> unsigned int i;
> - int ret;
> + int ret = 0;
>
> if (q->streaming) {
> dprintk(q, 1, "streaming active\n");
> @@ -857,17 +857,22 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
> /*
> * Make sure the requested values and current defaults are sane.
> */
> - WARN_ON(q->min_buffers_needed > VB2_MAX_FRAME);
> num_buffers = max_t(unsigned int, *count, q->min_buffers_needed);
> - num_buffers = min_t(unsigned int, num_buffers, VB2_MAX_FRAME);
> + num_buffers = min_t(unsigned int, num_buffers, q->max_num_buffers);
> memset(q->alloc_devs, 0, sizeof(q->alloc_devs));
> /*
> * Set this now to ensure that drivers see the correct q->memory value
> * in the queue_setup op.
> */
> mutex_lock(&q->mmap_lock);
> + if (!q->bufs)
> + q->bufs = kcalloc(q->max_num_buffers, sizeof(*q->bufs), GFP_KERNEL);
> + if (!q->bufs)
> + ret = -ENOMEM;
> q->memory = memory;
> mutex_unlock(&q->mmap_lock);
> + if (ret)
> + return ret;
> set_queue_coherency(q, non_coherent_mem);
>
> /*
> @@ -976,7 +981,7 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
> bool no_previous_buffers = !q_num_bufs;
> int ret = 0;
>
> - if (q_num_bufs == VB2_MAX_FRAME) {
> + if (q->num_buffers == q->max_num_buffers) {
> dprintk(q, 1, "maximum number of buffers already allocated\n");
> return -ENOBUFS;
> }
> @@ -993,7 +998,13 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
> */
> mutex_lock(&q->mmap_lock);
> q->memory = memory;
> + if (!q->bufs)
> + q->bufs = kcalloc(q->max_num_buffers, sizeof(*q->bufs), GFP_KERNEL);
> + if (!q->bufs)
> + ret = -ENOMEM;
> mutex_unlock(&q->mmap_lock);
> + if (ret)
> + return ret;
> q->waiting_for_buffers = !q->is_output;
> set_queue_coherency(q, non_coherent_mem);
> } else {
> @@ -1005,7 +1016,7 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
> return -EINVAL;
> }
>
> - num_buffers = min(*count, VB2_MAX_FRAME - q_num_bufs);
> + num_buffers = min(*count, q->max_num_buffers - q_num_bufs);
>
> if (requested_planes && requested_sizes) {
> num_planes = requested_planes;
> @@ -2465,6 +2476,12 @@ int vb2_core_queue_init(struct vb2_queue *q)
> /*
> * Sanity check
> */
> + if (!q->max_num_buffers)
> + q->max_num_buffers = VB2_MAX_FRAME;
> +
> + /* The maximum is limited by offset cookie encoding pattern */
> + q->max_num_buffers = min_t(unsigned int, q->max_num_buffers, MAX_BUFFER_INDEX);
> +
> if (WARN_ON(!q) ||
> WARN_ON(!q->ops) ||
> WARN_ON(!q->mem_ops) ||
> @@ -2474,6 +2491,10 @@ int vb2_core_queue_init(struct vb2_queue *q)
> WARN_ON(!q->ops->buf_queue))
> return -EINVAL;
>
> + if (WARN_ON(q->max_num_buffers > MAX_BUFFER_INDEX) ||
> + WARN_ON(q->min_buffers_needed > q->max_num_buffers))
> + return -EINVAL;
> +
> if (WARN_ON(q->requires_requests && !q->supports_requests))
> return -EINVAL;
>
> @@ -2519,7 +2540,9 @@ void vb2_core_queue_release(struct vb2_queue *q)
> __vb2_cleanup_fileio(q);
> __vb2_queue_cancel(q);
> mutex_lock(&q->mmap_lock);
> - __vb2_queue_free(q, vb2_get_num_buffers(q));
> + __vb2_queue_free(q, q->max_num_buffers);
> + kfree(q->bufs);
> + q->bufs = NULL;
> q->num_buffers = 0;
> mutex_unlock(&q->mmap_lock);
> }
> diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> index 7d798fb15c0b..f3cf4b235c1f 100644
> --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
> +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> @@ -627,7 +627,7 @@ struct vb2_buffer *vb2_find_buffer(struct vb2_queue *q, u64 timestamp)
> * This loop doesn't scale if there is a really large number of buffers.
> * Maybe something more efficient will be needed in this case.
> */
> - for (i = 0; i < vb2_get_num_buffers(q); i++) {
> + for (i = 0; i < q->max_num_buffers; i++) {
> vb2 = vb2_get_buffer(q, i);
>
> if (!vb2)
> @@ -1142,7 +1142,7 @@ int _vb2_fop_release(struct file *file, struct mutex *lock)
>
> if (lock)
> mutex_lock(lock);
> - if (file->private_data == vdev->queue->owner) {
> + if (!vdev->queue->owner || file->private_data == vdev->queue->owner) {
> vb2_queue_release(vdev->queue);
> vdev->queue->owner = NULL;
> }
> @@ -1270,7 +1270,7 @@ void vb2_video_unregister_device(struct video_device *vdev)
> */
> get_device(&vdev->dev);
> video_unregister_device(vdev);
> - if (vdev->queue && vdev->queue->owner) {
> + if (vdev->queue) {
> struct mutex *lock = vdev->queue->lock ?
> vdev->queue->lock : vdev->lock;
>
> diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
> index 8f9d9e4af5b1..e77a397195f2 100644
> --- a/include/media/videobuf2-core.h
> +++ b/include/media/videobuf2-core.h
> @@ -558,6 +558,7 @@ struct vb2_buf_ops {
> * @dma_dir: DMA mapping direction.
> * @bufs: videobuf2 buffer structures
> * @num_buffers: number of allocated/used buffers
> + * @max_num_buffers: upper limit of number of allocated/used buffers
> * @queued_list: list of buffers currently queued from userspace
> * @queued_count: number of buffers queued and ready for streaming.
> * @owned_by_drv_count: number of buffers owned by the driver
> @@ -619,8 +620,9 @@ struct vb2_queue {
> struct mutex mmap_lock;
> unsigned int memory;
> enum dma_data_direction dma_dir;
> - struct vb2_buffer *bufs[VB2_MAX_FRAME];
> + struct vb2_buffer **bufs;
> unsigned int num_buffers;
> + unsigned int max_num_buffers;
>
> struct list_head queued_list;
> unsigned int queued_count;
> @@ -1248,6 +1250,12 @@ static inline void vb2_clear_last_buffer_dequeued(struct vb2_queue *q)
> static inline struct vb2_buffer *vb2_get_buffer(struct vb2_queue *q,
> unsigned int index)
> {
> + if (!q->bufs)
> + return NULL;
> +
> + if (index >= q->max_num_buffers)
> + return NULL;
> +
> if (index < q->num_buffers)
> return q->bufs[index];
> return NULL;