Hi Hans,
Thanks a lot for pushing this, it looks super useful (I missed the v2).
On Sat, 2021-03-27 at 11:49 +0100, Hans Verkuil wrote:
> It can be hard to debug if all requests and request objects are correctly
> cleaned up when all related filehandles are closed.
>
> This patch adds a new 'requests' debugfs entry (if CONFIG_VIDEO_ADV_DEBUG
> is set) to report the number of open requests and request objects for a
> given media device node.
>
I have always associated CONFIG_VIDEO_ADV_DEBUG to VIDIOC_DBG_S/G_REGISTER
only. At least to me, re-using CONFIG_VIDEO_ADV_DEBUG is confusing: it's only
documented in the code what this debug option does.
How about just using CONFIG_DEBUG_FS, or adding a new one like
CONFIG_MEDIA_CONTROLLER_DEBUG or CONFIG_MEDIA_CONTROLLER_REQUEST_DEBUG?
(Coming to think about it, IMO the call-balance checks in drivers/media/common/videobuf2/videobuf2-core.c
should be behind a specific option named like CONFIG_VIDEOBUF2_DEBUG)
> Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
> ---
> This patch has been outstanding for too long, it is time that this is
> merged since it is really useful to have, especially for regression testing.
>
> Changes since v2:
> https://patchwork.linuxtv.org/project/linux-media/patch/20200818143719.102128-2-hverkuil-cisco@xs4all.nl/
>
> - Fix some CamelCase occurances in comments
> ---
> drivers/media/mc/mc-device.c | 27 +++++++++++++++++++++++++++
> drivers/media/mc/mc-devnode.c | 13 +++++++++++++
> drivers/media/mc/mc-request.c | 5 +++++
> include/media/media-device.h | 9 +++++++++
> include/media/media-devnode.h | 4 ++++
> include/media/media-request.h | 2 ++
> 6 files changed, 60 insertions(+)
>
> diff --git a/drivers/media/mc/mc-device.c b/drivers/media/mc/mc-device.c
> index 9e56d2ad6b94..868ac3200eb7 100644
> --- a/drivers/media/mc/mc-device.c
> +++ b/drivers/media/mc/mc-device.c
> @@ -691,6 +691,23 @@ void media_device_unregister_entity(struct media_entity *entity)
> }
> EXPORT_SYMBOL_GPL(media_device_unregister_entity);
>
> +#if IS_ENABLED(CONFIG_DEBUG_FS) && IS_ENABLED(CONFIG_VIDEO_ADV_DEBUG)
> +/*
> + * Log the state of media requests.
> + * Very useful for debugging.
> + */
> +static int media_device_requests(struct seq_file *file, void *priv)
> +{
> + struct media_device *dev = dev_get_drvdata(file->private);
> +
> + seq_printf(file, "number of requests: %d\n",
> + atomic_read(&dev->num_requests));
> + seq_printf(file, "number of request objects: %d\n",
> + atomic_read(&dev->num_request_objects));
Is it not better to print some entry per-requests and per-request objects
instead of counters?
I.e. for each request we create a file entry, and that file entry
would read the objects.
Thanks,
Ezequiel
@@ -691,6 +691,23 @@ void media_device_unregister_entity(struct media_entity *entity)
}
EXPORT_SYMBOL_GPL(media_device_unregister_entity);
+#if IS_ENABLED(CONFIG_DEBUG_FS) && IS_ENABLED(CONFIG_VIDEO_ADV_DEBUG)
+/*
+ * Log the state of media requests.
+ * Very useful for debugging.
+ */
+static int media_device_requests(struct seq_file *file, void *priv)
+{
+ struct media_device *dev = dev_get_drvdata(file->private);
+
+ seq_printf(file, "number of requests: %d\n",
+ atomic_read(&dev->num_requests));
+ seq_printf(file, "number of request objects: %d\n",
+ atomic_read(&dev->num_request_objects));
+ return 0;
+}
+#endif
+
/**
* media_device_init() - initialize a media device
* @mdev: The media device
@@ -714,6 +731,8 @@ void media_device_init(struct media_device *mdev)
ida_init(&mdev->entity_internal_idx);
atomic_set(&mdev->request_id, 0);
+ atomic_set(&mdev->num_requests, 0);
+ atomic_set(&mdev->num_request_objects, 0);
dev_dbg(mdev->dev, "Media device initialized\n");
}
@@ -766,6 +785,13 @@ int __must_check __media_device_register(struct media_device *mdev,
dev_dbg(mdev->dev, "Media device registered\n");
+#if IS_ENABLED(CONFIG_DEBUG_FS) && IS_ENABLED(CONFIG_VIDEO_ADV_DEBUG)
+ mdev->media_dir = debugfs_create_dir(dev_name(&devnode->dev),
+ media_top_dir);
+ debugfs_create_devm_seqfile(&devnode->dev, "requests",
+ mdev->media_dir, media_device_requests);
+#endif
+
return 0;
}
EXPORT_SYMBOL_GPL(__media_device_register);
@@ -843,6 +869,7 @@ void media_device_unregister(struct media_device *mdev)
dev_dbg(mdev->dev, "Media device unregistered\n");
+ debugfs_remove_recursive(mdev->media_dir);
device_remove_file(&mdev->devnode->dev, &dev_attr_model);
media_devnode_unregister(mdev->devnode);
/* devnode free is handled in media_devnode_*() */
@@ -45,6 +45,12 @@ static dev_t media_dev_t;
static DEFINE_MUTEX(media_devnode_lock);
static DECLARE_BITMAP(media_devnode_nums, MEDIA_NUM_DEVICES);
+/*
+ * debugfs
+ */
+struct dentry *media_top_dir;
+
+
/* Called when the last user of the media device exits. */
static void media_devnode_release(struct device *cd)
{
@@ -252,6 +258,8 @@ int __must_check media_devnode_register(struct media_device *mdev,
goto cdev_add_error;
}
+ dev_set_drvdata(&devnode->dev, mdev);
+
/* Part 4: Activate this minor. The char device can now be used. */
set_bit(MEDIA_FLAG_REGISTERED, &devnode->flags);
@@ -304,6 +312,10 @@ static int __init media_devnode_init(void)
return ret;
}
+#if IS_ENABLED(CONFIG_DEBUG_FS) && IS_ENABLED(CONFIG_VIDEO_ADV_DEBUG)
+ media_top_dir = debugfs_create_dir("media", NULL);
+#endif
+
ret = bus_register(&media_bus_type);
if (ret < 0) {
unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES);
@@ -316,6 +328,7 @@ static int __init media_devnode_init(void)
static void __exit media_devnode_exit(void)
{
+ debugfs_remove_recursive(media_top_dir);
bus_unregister(&media_bus_type);
unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES);
}
@@ -74,6 +74,7 @@ static void media_request_release(struct kref *kref)
mdev->ops->req_free(req);
else
kfree(req);
+ atomic_dec(&mdev->num_requests);
}
void media_request_put(struct media_request *req)
@@ -330,6 +331,7 @@ int media_request_alloc(struct media_device *mdev, int *alloc_fd)
snprintf(req->debug_str, sizeof(req->debug_str), "%u:%d",
atomic_inc_return(&mdev->request_id), fd);
+ atomic_inc(&mdev->num_requests);
dev_dbg(mdev->dev, "request: allocated %s\n", req->debug_str);
fd_install(fd, filp);
@@ -357,6 +359,7 @@ static void media_request_object_release(struct kref *kref)
if (WARN_ON(req))
media_request_object_unbind(obj);
obj->ops->release(obj);
+ atomic_dec(&obj->mdev->num_request_objects);
}
struct media_request_object *
@@ -420,6 +423,7 @@ int media_request_object_bind(struct media_request *req,
obj->req = req;
obj->ops = ops;
obj->priv = priv;
+ obj->mdev = req->mdev;
if (is_buffer)
list_add_tail(&obj->list, &req->objects);
@@ -427,6 +431,7 @@ int media_request_object_bind(struct media_request *req,
list_add(&obj->list, &req->objects);
req->num_incomplete_objects++;
ret = 0;
+ atomic_inc(&obj->mdev->num_request_objects);
unlock:
spin_unlock_irqrestore(&req->lock, flags);
@@ -13,6 +13,7 @@
#include <linux/list.h>
#include <linux/mutex.h>
+#include <linux/atomic.h>
#include <media/media-devnode.h>
#include <media/media-entity.h>
@@ -106,6 +107,9 @@ struct media_device_ops {
* @req_queue_mutex: Serialise the MEDIA_REQUEST_IOC_QUEUE ioctl w.r.t.
* other operations that stop or start streaming.
* @request_id: Used to generate unique request IDs
+ * @num_requests: number of associated requests
+ * @num_request_objects: number of associated request objects
+ * @media_dir: debugfs media directory
*
* This structure represents an abstract high-level media device. It allows easy
* access to entities and provides basic media device-level support. The
@@ -179,6 +183,11 @@ struct media_device {
struct mutex req_queue_mutex;
atomic_t request_id;
+ atomic_t num_requests;
+ atomic_t num_request_objects;
+
+ /* debugfs */
+ struct dentry *media_dir;
};
/* We don't need to include pci.h or usb.h here */
@@ -20,9 +20,13 @@
#include <linux/fs.h>
#include <linux/device.h>
#include <linux/cdev.h>
+#include <linux/debugfs.h>
struct media_device;
+/* debugfs top-level media directory */
+extern struct dentry *media_top_dir;
+
/*
* Flag to mark the media_devnode struct as registered. Drivers must not touch
* this flag directly, it will be set and cleared by media_devnode_register and
@@ -256,6 +256,7 @@ struct media_request_object_ops {
* struct media_request_object - An opaque object that belongs to a media
* request
*
+ * @mdev: media device this object belongs to
* @ops: object's operations
* @priv: object's priv pointer
* @req: the request this object belongs to (can be NULL)
@@ -267,6 +268,7 @@ struct media_request_object_ops {
* another struct that contains the actual data for this request object.
*/
struct media_request_object {
+ struct media_device *mdev;
const struct media_request_object_ops *ops;
void *priv;
struct media_request *req;