Re: [PATCH v3] em28xx: Only deallocate struct em28xx after finishing all extensions

["Frank Schäfer" <fschaefer.oss@googlemail.com>]

Am 05.03.2014 15:22, schrieb Mauro Carvalho Chehab:
> We can't free struct em28xx while one of the extensions is still
> using it.
>
> So, add a kref() to control it, freeing it only after the
> extensions fini calls.
>
> Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>
> ---
>  drivers/media/usb/em28xx/em28xx-audio.c |  7 ++++++-
>  drivers/media/usb/em28xx/em28xx-cards.c | 31 ++++++++++++++++++++++++-------
>  drivers/media/usb/em28xx/em28xx-dvb.c   |  6 +++++-
>  drivers/media/usb/em28xx/em28xx-input.c |  8 +++++++-
>  drivers/media/usb/em28xx/em28xx-video.c | 15 ++++++++-------
>  drivers/media/usb/em28xx/em28xx.h       |  8 ++++++--
>  6 files changed, 56 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/media/usb/em28xx/em28xx-audio.c b/drivers/media/usb/em28xx/em28xx-audio.c
> index 0f5b6f3e7a3f..f75c0a5494d6 100644
> --- a/drivers/media/usb/em28xx/em28xx-audio.c
> +++ b/drivers/media/usb/em28xx/em28xx-audio.c
> @@ -301,6 +301,7 @@ static int snd_em28xx_capture_open(struct snd_pcm_substream *substream)
>  			goto err;
>  	}
>  
> +	kref_get(&dev->ref);
>  	dev->adev.users++;
>  	mutex_unlock(&dev->lock);
>  
> @@ -341,6 +342,7 @@ static int snd_em28xx_pcm_close(struct snd_pcm_substream *substream)
>  		substream->runtime->dma_area = NULL;
>  	}
>  	mutex_unlock(&dev->lock);
> +	kref_put(&dev->ref, em28xx_free_device);
>  
>  	return 0;
>  }
> @@ -895,6 +897,8 @@ static int em28xx_audio_init(struct em28xx *dev)
>  
>  	em28xx_info("Binding audio extension\n");
>  
> +	kref_get(&dev->ref);
> +
>  	printk(KERN_INFO "em28xx-audio.c: Copyright (C) 2006 Markus "
>  			 "Rechberger\n");
>  	printk(KERN_INFO
> @@ -967,7 +971,7 @@ static int em28xx_audio_fini(struct em28xx *dev)
>  	if (dev == NULL)
>  		return 0;
>  
> -	if (dev->has_alsa_audio != 1) {
> +	if (!dev->has_alsa_audio) {
>  		/* This device does not support the extension (in this case
>  		   the device is expecting the snd-usb-audio module or
>  		   doesn't have analog audio support at all) */
> @@ -986,6 +990,7 @@ static int em28xx_audio_fini(struct em28xx *dev)
>  		dev->adev.sndcard = NULL;
>  	}
>  
> +	kref_put(&dev->ref, em28xx_free_device);
>  	return 0;
>  }
>  
> diff --git a/drivers/media/usb/em28xx/em28xx-cards.c b/drivers/media/usb/em28xx/em28xx-cards.c
> index 2fb300e882f0..512448b757c9 100644
> --- a/drivers/media/usb/em28xx/em28xx-cards.c
> +++ b/drivers/media/usb/em28xx/em28xx-cards.c
> @@ -2939,7 +2939,7 @@ static void flush_request_modules(struct em28xx *dev)
>   * unregisters the v4l2,i2c and usb devices
>   * called when the device gets disconnected or at module unload
>  */
> -void em28xx_release_resources(struct em28xx *dev)
> +static void em28xx_release_resources(struct em28xx *dev)
>  {
>  	/*FIXME: I2C IR should be disconnected */
>  
> @@ -2956,7 +2956,26 @@ void em28xx_release_resources(struct em28xx *dev)
>  
>  	mutex_unlock(&dev->lock);
>  };
> -EXPORT_SYMBOL_GPL(em28xx_release_resources);
> +
> +/**
> + * em28xx_free_defice() - Free em28xx device
> + *
> + * @ref: struct kref for em28xx device
> + *
> + * This is called when all extensions and em28xx core unregisters a device
> + */
> +void em28xx_free_device(struct kref *ref)
> +{
> +	struct em28xx *dev = kref_to_dev(ref);
> +
> +	em28xx_info("Freeing device\n");
> +
> +	if (!dev->disconnected)
> +		em28xx_release_resources(dev);
Hmm... good catch !

> +
> +	kfree(dev->alt_max_pkt_size_isoc);
> +	kfree(dev);
> +}
>  
>  /*
>   * em28xx_init_dev()
> @@ -3409,6 +3428,8 @@ static int em28xx_usb_probe(struct usb_interface *interface,
>  			    dev->dvb_xfer_bulk ? "bulk" : "isoc");
>  	}
>  
> +	kref_init(&dev->ref);
> +
>  	request_modules(dev);
>  
>  	/* Should be the last thing to do, to avoid newer udev's to
> @@ -3453,11 +3474,7 @@ static void em28xx_usb_disconnect(struct usb_interface *interface)
>  	em28xx_close_extension(dev);
>  
>  	em28xx_release_resources(dev);
> -
> -	if (!dev->users) {
> -		kfree(dev->alt_max_pkt_size_isoc);
> -		kfree(dev);
> -	}
> +	kref_put(&dev->ref, em28xx_free_device);
>  }
>  
>  static int em28xx_usb_suspend(struct usb_interface *interface,
> diff --git a/drivers/media/usb/em28xx/em28xx-dvb.c b/drivers/media/usb/em28xx/em28xx-dvb.c
> index d4986bdfbdc3..6dbc71ba2820 100644
> --- a/drivers/media/usb/em28xx/em28xx-dvb.c
> +++ b/drivers/media/usb/em28xx/em28xx-dvb.c
> @@ -1043,7 +1043,6 @@ static int em28xx_dvb_init(struct em28xx *dev)
>  	em28xx_info("Binding DVB extension\n");
>  
>  	dvb = kzalloc(sizeof(struct em28xx_dvb), GFP_KERNEL);
> -
>  	if (dvb == NULL) {
>  		em28xx_info("em28xx_dvb: memory allocation failed\n");
>  		return -ENOMEM;
> @@ -1521,6 +1520,9 @@ static int em28xx_dvb_init(struct em28xx *dev)
>  	dvb->adapter.mfe_shared = mfe_shared;
>  
>  	em28xx_info("DVB extension successfully initialized\n");
> +
> +	kref_get(&dev->ref);
> +

The fini() functions are always called, even if an error occured in init().
So (in opposition to the open()/close() functions) kref_get() needs to
be called at the beginning of the init() methods.

"dev->is_audio_only" and "!dev->board.has_dvb" is checked in both
functions (init+fini), so the right place here is one line before or after

    em28xx_info("Binding DVB extension\n");


Everything else looks good.

Regards,
Frank

>  ret:
>  	em28xx_set_mode(dev, EM28XX_SUSPEND);
>  	mutex_unlock(&dev->lock);
> @@ -1579,6 +1581,8 @@ static int em28xx_dvb_fini(struct em28xx *dev)
>  		dev->dvb = NULL;
>  	}
>  
> +	kref_put(&dev->ref, em28xx_free_device);
> +
>  	return 0;
>  }
>  
> diff --git a/drivers/media/usb/em28xx/em28xx-input.c b/drivers/media/usb/em28xx/em28xx-input.c
> index 47a2c1dcccbf..2a9bf667f208 100644
> --- a/drivers/media/usb/em28xx/em28xx-input.c
> +++ b/drivers/media/usb/em28xx/em28xx-input.c
> @@ -676,6 +676,8 @@ static int em28xx_ir_init(struct em28xx *dev)
>  		return 0;
>  	}
>  
> +	kref_get(&dev->ref);
> +
>  	if (dev->board.buttons)
>  		em28xx_init_buttons(dev);
>  
> @@ -816,7 +818,7 @@ static int em28xx_ir_fini(struct em28xx *dev)
>  
>  	/* skip detach on non attached boards */
>  	if (!ir)
> -		return 0;
> +		goto ref_put;
>  
>  	if (ir->rc)
>  		rc_unregister_device(ir->rc);
> @@ -824,6 +826,10 @@ static int em28xx_ir_fini(struct em28xx *dev)
>  	/* done */
>  	kfree(ir);
>  	dev->ir = NULL;
> +
> +ref_put:
> +	kref_put(&dev->ref, em28xx_free_device);
> +
>  	return 0;
>  }
>  
> diff --git a/drivers/media/usb/em28xx/em28xx-video.c b/drivers/media/usb/em28xx/em28xx-video.c
> index 19af6b3e9e2b..32aa55f033fc 100644
> --- a/drivers/media/usb/em28xx/em28xx-video.c
> +++ b/drivers/media/usb/em28xx/em28xx-video.c
> @@ -1837,7 +1837,6 @@ static int em28xx_v4l2_open(struct file *filp)
>  			video_device_node_name(vdev), v4l2_type_names[fh_type],
>  			dev->users);
>  
> -
>  	if (mutex_lock_interruptible(&dev->lock))
>  		return -ERESTARTSYS;
>  	fh = kzalloc(sizeof(struct em28xx_fh), GFP_KERNEL);
> @@ -1869,6 +1868,7 @@ static int em28xx_v4l2_open(struct file *filp)
>  		v4l2_device_call_all(&dev->v4l2_dev, 0, tuner, s_radio);
>  	}
>  
> +	kref_get(&dev->ref);
>  	dev->users++;
>  
>  	mutex_unlock(&dev->lock);
> @@ -1926,9 +1926,8 @@ static int em28xx_v4l2_fini(struct em28xx *dev)
>  		dev->clk = NULL;
>  	}
>  
> -	if (dev->users)
> -		em28xx_warn("Device is open ! Memory deallocation is deferred on last close.\n");
>  	mutex_unlock(&dev->lock);
> +	kref_put(&dev->ref, em28xx_free_device);
>  
>  	return 0;
>  }
> @@ -1976,11 +1975,9 @@ static int em28xx_v4l2_close(struct file *filp)
>  	mutex_lock(&dev->lock);
>  
>  	if (dev->users == 1) {
> -		/* free the remaining resources if device is disconnected */
> -		if (dev->disconnected) {
> -			kfree(dev->alt_max_pkt_size_isoc);
> +		/* No sense to try to write to the device */
> +		if (dev->disconnected)
>  			goto exit;
> -		}
>  
>  		/* Save some power by putting tuner to sleep */
>  		v4l2_device_call_all(&dev->v4l2_dev, 0, core, s_power, 0);
> @@ -2001,6 +1998,8 @@ static int em28xx_v4l2_close(struct file *filp)
>  exit:
>  	dev->users--;
>  	mutex_unlock(&dev->lock);
> +	kref_put(&dev->ref, em28xx_free_device);
> +
>  	return 0;
>  }
>  
> @@ -2515,6 +2514,8 @@ static int em28xx_v4l2_init(struct em28xx *dev)
>  
>  	em28xx_info("V4L2 extension successfully initialized\n");
>  
> +	kref_get(&dev->ref);
> +
>  	mutex_unlock(&dev->lock);
>  	return 0;
>  
> diff --git a/drivers/media/usb/em28xx/em28xx.h b/drivers/media/usb/em28xx/em28xx.h
> index 9e44f5bfc48b..2051fc9fb932 100644
> --- a/drivers/media/usb/em28xx/em28xx.h
> +++ b/drivers/media/usb/em28xx/em28xx.h
> @@ -32,6 +32,7 @@
>  #include <linux/workqueue.h>
>  #include <linux/i2c.h>
>  #include <linux/mutex.h>
> +#include <linux/kref.h>
>  #include <linux/videodev2.h>
>  
>  #include <media/videobuf2-vmalloc.h>
> @@ -536,9 +537,10 @@ struct em28xx_i2c_bus {
>  	enum em28xx_i2c_algo_type algo_type;
>  };
>  
> -
>  /* main device struct */
>  struct em28xx {
> +	struct kref ref;
> +
>  	/* generic device properties */
>  	char name[30];		/* name (including minor) of the device */
>  	int model;		/* index in the device_data struct */
> @@ -710,6 +712,8 @@ struct em28xx {
>  	struct em28xx_dvb *dvb;
>  };
>  
> +#define kref_to_dev(d) container_of(d, struct em28xx, ref)
> +
>  struct em28xx_ops {
>  	struct list_head next;
>  	char *name;
> @@ -771,7 +775,7 @@ extern struct em28xx_board em28xx_boards[];
>  extern struct usb_device_id em28xx_id_table[];
>  int em28xx_tuner_callback(void *ptr, int component, int command, int arg);
>  void em28xx_setup_xc3028(struct em28xx *dev, struct xc2028_ctrl *ctl);
> -void em28xx_release_resources(struct em28xx *dev);
> +void em28xx_free_device(struct kref *ref);
>  
>  /* Provided by em28xx-camera.c */
>  int em28xx_detect_sensor(struct em28xx *dev);