Re: [PATCH 3/7] em28xx: Only deallocate struct em28xx after finishing all extensions

Frank Schäfer <fschaefer.oss@xxxxxxxxxxxxxx> · Mon, 13 Jan 2014 20:02:19 +0100

On 13.01.2014 00:00, Mauro Carvalho Chehab wrote:
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@xxxxxxxxxxx>
---
  drivers/media/usb/em28xx/em28xx-audio.c |  5 ++++-
  drivers/media/usb/em28xx/em28xx-cards.c | 34 ++++++++++++++++-----------------
  drivers/media/usb/em28xx/em28xx-dvb.c   |  5 ++++-
  drivers/media/usb/em28xx/em28xx-input.c |  8 +++++++-
  drivers/media/usb/em28xx/em28xx-video.c | 11 +++++------
  drivers/media/usb/em28xx/em28xx.h       |  9 +++++++--
  6 files changed, 44 insertions(+), 28 deletions(-)

diff --git a/drivers/media/usb/em28xx/em28xx-audio.c b/drivers/media/usb/em28xx/em28xx-audio.c
index 97d9105e6830..8e959dae8358 100644
--- a/drivers/media/usb/em28xx/em28xx-audio.c
+++ b/drivers/media/usb/em28xx/em28xx-audio.c
@@ -878,6 +878,8 @@ 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
@@ -949,7 +951,7 @@ 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) */
@@ -963,6 +965,7 @@ 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 3b332d527ccb..df92f417634a 100644
--- a/drivers/media/usb/em28xx/em28xx-cards.c
+++ b/drivers/media/usb/em28xx/em28xx-cards.c
@@ -2867,16 +2867,18 @@ static void flush_request_modules(struct em28xx *dev)
  	flush_work(&dev->request_module_wk);
  }
  
-/*
- * em28xx_release_resources()
- * unregisters the v4l2,i2c and usb devices
- * called when the device gets disconnected or at module unload
-*/
-void em28xx_release_resources(struct em28xx *dev)
+/**
+ * em28xx_release_resources() -  unregisters the v4l2,i2c and usb devices
+ *
+ * @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)
  {
-	/*FIXME: I2C IR should be disconnected */
+	struct em28xx *dev = kref_to_dev(ref);
  
-	mutex_lock(&dev->lock);
+	em28xx_info("Freeing device\n");
  
  	if (dev->def_i2c_bus)
  		em28xx_i2c_unregister(dev, 1);
@@ -2887,9 +2889,10 @@ void em28xx_release_resources(struct em28xx *dev)
  	/* Mark device as unused */
  	clear_bit(dev->devno, &em28xx_devused);
  
-	mutex_unlock(&dev->lock);
-};
-EXPORT_SYMBOL_GPL(em28xx_release_resources);
+	kfree(dev->alt_max_pkt_size_isoc);
+	kfree(dev);
+}
+EXPORT_SYMBOL_GPL(em28xx_free_device);
  
  /*
   * em28xx_init_dev()
@@ -3342,6 +3345,8 @@ 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
@@ -3390,12 +3395,7 @@ 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 struct usb_driver em28xx_usb_driver = {
diff --git a/drivers/media/usb/em28xx/em28xx-dvb.c b/drivers/media/usb/em28xx/em28xx-dvb.c
index 5ea563e3f0e4..8674ae5fce06 100644
--- a/drivers/media/usb/em28xx/em28xx-dvb.c
+++ b/drivers/media/usb/em28xx/em28xx-dvb.c
@@ -1010,11 +1010,11 @@ 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;
  	}
+	kref_get(&dev->ref);
  	dev->dvb = dvb;
  	dvb->fe[0] = dvb->fe[1] = NULL;
  
@@ -1442,6 +1442,7 @@ static int em28xx_dvb_init(struct em28xx *dev)
  	dvb->adapter.mfe_shared = mfe_shared;
  
  	em28xx_info("DVB extension successfully initialized\n");
+
  ret:
  	em28xx_set_mode(dev, EM28XX_SUSPEND);
  	mutex_unlock(&dev->lock);
@@ -1492,6 +1493,8 @@ 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 61c061f3a476..33388b5922a0 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);
  
@@ -814,7 +816,7 @@ 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);
@@ -822,6 +824,10 @@ 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 587ff3fe9402..dc10cec772ba 100644
--- a/drivers/media/usb/em28xx/em28xx-video.c
+++ b/drivers/media/usb/em28xx/em28xx-video.c
@@ -1922,8 +1922,7 @@ static int em28xx_v4l2_fini(struct em28xx *dev)
  	v4l2_ctrl_handler_free(&dev->ctrl_handler);
  	v4l2_device_unregister(&dev->v4l2_dev);
  
-	if (dev->users)
-		em28xx_warn("Device is open ! Memory deallocation is deferred on last close.\n");
+	kref_put(&dev->ref, em28xx_free_device);
  
  	return 0;
  }
@@ -1945,11 +1944,9 @@ 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);
@@ -2201,6 +2198,8 @@ static int em28xx_v4l2_init(struct em28xx *dev)
  
  	em28xx_info("Registering V4L2 extension\n");
  
+	kref_get(&dev->ref);
+
  	mutex_lock(&dev->lock);
  
  	ret = v4l2_device_register(&dev->udev->dev, &dev->v4l2_dev);
diff --git a/drivers/media/usb/em28xx/em28xx.h b/drivers/media/usb/em28xx/em28xx.h
index 5d5d1b6f0294..d38c08e4da60 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>
@@ -531,9 +532,11 @@ 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 */
@@ -706,6 +709,8 @@ 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;
@@ -763,7 +768,7 @@ 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);
I welcome this patch and the general approach looks good.
I had started working on the same issue, but it's not that trivial.

At first glance there seem to be several issues, but I will need to 
review this patch in more detail and also make some tests.
Unfortunately, I don't have much time this evening, So could you please 
hold it back another day ?
I hope I can review the other remaining patch of this series (patch 5/7) 
later this evening.

Regards,
Frank
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