[RFC/RFT 4/5] Input: mousedev - implement proper locking

[Dmitry Torokhov <dtor@insightbb.com>]

[-- Attachment #1: mousedev-locking.patch --]
[-- Type: text/plain, Size: 31449 bytes --]

Input: mousedev - implement proper locking

Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
---

 drivers/input/mousedev.c |  736 +++++++++++++++++++++++++++++------------------
 1 files changed, 464 insertions(+), 272 deletions(-)

Index: work/drivers/input/mousedev.c
===================================================================
--- work.orig/drivers/input/mousedev.c
+++ work/drivers/input/mousedev.c
@@ -61,9 +61,11 @@ struct mousedev {
 	int open;
 	int minor;
 	char name[16];
+	struct input_handle handle;
 	wait_queue_head_t wait;
 	struct list_head client_list;
-	struct input_handle handle;
+	spinlock_t client_lock; /* protects client_list */
+	struct mutex mutex;
 	struct device dev;
 
 	struct list_head mixdev_node;
@@ -113,108 +115,137 @@ static unsigned char mousedev_imex_seq[]
 static struct input_handler mousedev_handler;
 
 static struct mousedev *mousedev_table[MOUSEDEV_MINORS];
+static DEFINE_MUTEX(mousedev_table_mutex);
 static struct mousedev *mousedev_mix;
 static LIST_HEAD(mousedev_mix_list);
 
+static void mixdev_open_devices(void);
+static void mixdev_close_devices(void);
+
 #define fx(i)  (mousedev->old_x[(mousedev->pkt_count - (i)) & 03])
 #define fy(i)  (mousedev->old_y[(mousedev->pkt_count - (i)) & 03])
 
-static void mousedev_touchpad_event(struct input_dev *dev, struct mousedev *mousedev, unsigned int code, int value)
+static void mousedev_touchpad_event(struct input_dev *dev,
+				    struct mousedev *mousedev,
+				    unsigned int code, int value)
 {
 	int size, tmp;
 	enum { FRACTION_DENOM = 128 };
 
 	switch (code) {
-		case ABS_X:
-			fx(0) = value;
-			if (mousedev->touch && mousedev->pkt_count >= 2) {
-				size = dev->absmax[ABS_X] - dev->absmin[ABS_X];
-				if (size == 0)
-					size = 256 * 2;
-				tmp = ((value - fx(2)) * (256 * FRACTION_DENOM)) / size;
-				tmp += mousedev->frac_dx;
-				mousedev->packet.dx = tmp / FRACTION_DENOM;
-				mousedev->frac_dx = tmp - mousedev->packet.dx * FRACTION_DENOM;
-			}
-			break;
 
-		case ABS_Y:
-			fy(0) = value;
-			if (mousedev->touch && mousedev->pkt_count >= 2) {
-				/* use X size to keep the same scale */
-				size = dev->absmax[ABS_X] - dev->absmin[ABS_X];
-				if (size == 0)
-					size = 256 * 2;
-				tmp = -((value - fy(2)) * (256 * FRACTION_DENOM)) / size;
-				tmp += mousedev->frac_dy;
-				mousedev->packet.dy = tmp / FRACTION_DENOM;
-				mousedev->frac_dy = tmp - mousedev->packet.dy * FRACTION_DENOM;
-			}
-			break;
+	case ABS_X:
+		fx(0) = value;
+		if (mousedev->touch && mousedev->pkt_count >= 2) {
+			size = dev->absmax[ABS_X] - dev->absmin[ABS_X];
+			if (size == 0)
+				size = 256 * 2;
+			tmp = ((value - fx(2)) * 256 * FRACTION_DENOM) / size;
+			tmp += mousedev->frac_dx;
+			mousedev->packet.dx = tmp / FRACTION_DENOM;
+			mousedev->frac_dx =
+				tmp - mousedev->packet.dx * FRACTION_DENOM;
+		}
+		break;
+
+	case ABS_Y:
+		fy(0) = value;
+		if (mousedev->touch && mousedev->pkt_count >= 2) {
+			/* use X size to keep the same scale */
+			size = dev->absmax[ABS_X] - dev->absmin[ABS_X];
+			if (size == 0)
+				size = 256 * 2;
+			tmp = -((value - fy(2)) * 256 * FRACTION_DENOM) / size;
+			tmp += mousedev->frac_dy;
+			mousedev->packet.dy = tmp / FRACTION_DENOM;
+			mousedev->frac_dy = tmp -
+				mousedev->packet.dy * FRACTION_DENOM;
+		}
+		break;
 	}
 }
 
-static void mousedev_abs_event(struct input_dev *dev, struct mousedev *mousedev, unsigned int code, int value)
+static void mousedev_abs_event(struct input_dev *dev, struct mousedev *mousedev,
+				unsigned int code, int value)
 {
 	int size;
 
 	switch (code) {
-		case ABS_X:
-			size = dev->absmax[ABS_X] - dev->absmin[ABS_X];
-			if (size == 0)
-				size = xres ? : 1;
-			if (value > dev->absmax[ABS_X])
-				value = dev->absmax[ABS_X];
-			if (value < dev->absmin[ABS_X])
-				value = dev->absmin[ABS_X];
-			mousedev->packet.x = ((value - dev->absmin[ABS_X]) * xres) / size;
-			mousedev->packet.abs_event = 1;
-			break;
 
-		case ABS_Y:
-			size = dev->absmax[ABS_Y] - dev->absmin[ABS_Y];
-			if (size == 0)
-				size = yres ? : 1;
-			if (value > dev->absmax[ABS_Y])
-				value = dev->absmax[ABS_Y];
-			if (value < dev->absmin[ABS_Y])
-				value = dev->absmin[ABS_Y];
-			mousedev->packet.y = yres - ((value - dev->absmin[ABS_Y]) * yres) / size;
-			mousedev->packet.abs_event = 1;
-			break;
+	case ABS_X:
+		size = dev->absmax[ABS_X] - dev->absmin[ABS_X];
+		if (size == 0)
+			size = xres ? : 1;
+		if (value > dev->absmax[ABS_X])
+			value = dev->absmax[ABS_X];
+		if (value < dev->absmin[ABS_X])
+			value = dev->absmin[ABS_X];
+		mousedev->packet.x =
+			((value - dev->absmin[ABS_X]) * xres) / size;
+		mousedev->packet.abs_event = 1;
+		break;
+
+	case ABS_Y:
+		size = dev->absmax[ABS_Y] - dev->absmin[ABS_Y];
+		if (size == 0)
+			size = yres ? : 1;
+		if (value > dev->absmax[ABS_Y])
+			value = dev->absmax[ABS_Y];
+		if (value < dev->absmin[ABS_Y])
+			value = dev->absmin[ABS_Y];
+		mousedev->packet.y = yres -
+			((value - dev->absmin[ABS_Y]) * yres) / size;
+		mousedev->packet.abs_event = 1;
+		break;
 	}
 }
 
-static void mousedev_rel_event(struct mousedev *mousedev, unsigned int code, int value)
+static void mousedev_rel_event(struct mousedev *mousedev,
+				unsigned int code, int value)
 {
 	switch (code) {
-		case REL_X:	mousedev->packet.dx += value; break;
-		case REL_Y:	mousedev->packet.dy -= value; break;
-		case REL_WHEEL:	mousedev->packet.dz -= value; break;
+	case REL_X:
+		mousedev->packet.dx += value;
+		break;
+
+	case REL_Y:
+		mousedev->packet.dy -= value;
+		break;
+
+	case REL_WHEEL:
+		mousedev->packet.dz -= value;
+		break;
 	}
 }
 
-static void mousedev_key_event(struct mousedev *mousedev, unsigned int code, int value)
+static void mousedev_key_event(struct mousedev *mousedev,
+				unsigned int code, int value)
 {
 	int index;
 
 	switch (code) {
-		case BTN_TOUCH:
-		case BTN_0:
-		case BTN_LEFT:		index = 0; break;
-		case BTN_STYLUS:
-		case BTN_1:
-		case BTN_RIGHT:		index = 1; break;
-		case BTN_2:
-		case BTN_FORWARD:
-		case BTN_STYLUS2:
-		case BTN_MIDDLE:	index = 2; break;
-		case BTN_3:
-		case BTN_BACK:
-		case BTN_SIDE:		index = 3; break;
-		case BTN_4:
-		case BTN_EXTRA:		index = 4; break;
-		default:		return;
+
+	case BTN_TOUCH:
+	case BTN_0:
+	case BTN_LEFT:		index = 0; break;
+
+	case BTN_STYLUS:
+	case BTN_1:
+	case BTN_RIGHT:		index = 1; break;
+
+	case BTN_2:
+	case BTN_FORWARD:
+	case BTN_STYLUS2:
+	case BTN_MIDDLE:	index = 2; break;
+
+	case BTN_3:
+	case BTN_BACK:
+	case BTN_SIDE:		index = 3; break;
+
+	case BTN_4:
+	case BTN_EXTRA:		index = 4; break;
+
+	default:		return;
 	}
 
 	if (value) {
@@ -226,19 +257,22 @@ static void mousedev_key_event(struct mo
 	}
 }
 
-static void mousedev_notify_readers(struct mousedev *mousedev, struct mousedev_hw_data *packet)
+static void mousedev_notify_readers(struct mousedev *mousedev,
+				    struct mousedev_hw_data *packet)
 {
 	struct mousedev_client *client;
 	struct mousedev_motion *p;
-	unsigned long flags;
+	unsigned int new_head;
 	int wake_readers = 0;
 
-	list_for_each_entry(client, &mousedev->client_list, node) {
-		spin_lock_irqsave(&client->packet_lock, flags);
+	list_for_each_entry_rcu(client, &mousedev->client_list, node) {
+
+		/* Just acquire the lock, interrupts already disabled */
+		spin_lock(&client->packet_lock);
 
 		p = &client->packets[client->head];
 		if (client->ready && p->buttons != mousedev->packet.buttons) {
-			unsigned int new_head = (client->head + 1) % PACKET_QUEUE_LEN;
+			new_head = (client->head + 1) % PACKET_QUEUE_LEN;
 			if (new_head != client->tail) {
 				p = &client->packets[client->head = new_head];
 				memset(p, 0, sizeof(struct mousedev_motion));
@@ -253,19 +287,22 @@ static void mousedev_notify_readers(stru
 		}
 
 		client->pos_x += packet->dx;
-		client->pos_x = client->pos_x < 0 ? 0 : (client->pos_x >= xres ? xres : client->pos_x);
+		client->pos_x = client->pos_x < 0 ?
+			0 : (client->pos_x >= xres ? xres : client->pos_x);
 		client->pos_y += packet->dy;
-		client->pos_y = client->pos_y < 0 ? 0 : (client->pos_y >= yres ? yres : client->pos_y);
+		client->pos_y = client->pos_y < 0 ?
+			0 : (client->pos_y >= yres ? yres : client->pos_y);
 
 		p->dx += packet->dx;
 		p->dy += packet->dy;
 		p->dz += packet->dz;
 		p->buttons = mousedev->packet.buttons;
 
-		if (p->dx || p->dy || p->dz || p->buttons != client->last_buttons)
+		if (p->dx || p->dy || p->dz ||
+		    p->buttons != client->last_buttons)
 			client->ready = 1;
 
-		spin_unlock_irqrestore(&client->packet_lock, flags);
+		spin_unlock(&client->packet_lock);
 
 		if (client->ready) {
 			kill_fasync(&client->fasync, SIGIO, POLL_IN);
@@ -281,7 +318,8 @@ static void mousedev_touchpad_touch(stru
 {
 	if (!value) {
 		if (mousedev->touch &&
-		    time_before(jiffies, mousedev->touch + msecs_to_jiffies(tap_time))) {
+		    time_before(jiffies,
+				mousedev->touch + msecs_to_jiffies(tap_time))) {
 			/*
 			 * Toggle left button to emulate tap.
 			 * We rely on the fact that mousedev_mix always has 0
@@ -290,7 +328,8 @@ static void mousedev_touchpad_touch(stru
 			set_bit(0, &mousedev->packet.buttons);
 			set_bit(0, &mousedev_mix->packet.buttons);
 			mousedev_notify_readers(mousedev, &mousedev_mix->packet);
-			mousedev_notify_readers(mousedev_mix, &mousedev_mix->packet);
+			mousedev_notify_readers(mousedev_mix,
+						&mousedev_mix->packet);
 			clear_bit(0, &mousedev->packet.buttons);
 			clear_bit(0, &mousedev_mix->packet.buttons);
 		}
@@ -302,54 +341,61 @@ static void mousedev_touchpad_touch(stru
 		mousedev->touch = jiffies;
 }
 
-static void mousedev_event(struct input_handle *handle, unsigned int type, unsigned int code, int value)
+static void mousedev_event(struct input_handle *handle,
+			   unsigned int type, unsigned int code, int value)
 {
 	struct mousedev *mousedev = handle->private;
 
 	switch (type) {
-		case EV_ABS:
-			/* Ignore joysticks */
-			if (test_bit(BTN_TRIGGER, handle->dev->keybit))
-				return;
 
-			if (test_bit(BTN_TOOL_FINGER, handle->dev->keybit))
-				mousedev_touchpad_event(handle->dev, mousedev, code, value);
+	case EV_ABS:
+		/* Ignore joysticks */
+		if (test_bit(BTN_TRIGGER, handle->dev->keybit))
+			return;
+
+		if (test_bit(BTN_TOOL_FINGER, handle->dev->keybit))
+			mousedev_touchpad_event(handle->dev,
+						mousedev, code, value);
+		else
+			mousedev_abs_event(handle->dev, mousedev, code, value);
+
+		break;
+
+	case EV_REL:
+		mousedev_rel_event(mousedev, code, value);
+		break;
+
+	case EV_KEY:
+		if (value != 2) {
+			if (code == BTN_TOUCH &&
+			    test_bit(BTN_TOOL_FINGER, handle->dev->keybit))
+				mousedev_touchpad_touch(mousedev, value);
 			else
-				mousedev_abs_event(handle->dev, mousedev, code, value);
-
-			break;
-
-		case EV_REL:
-			mousedev_rel_event(mousedev, code, value);
-			break;
+				mousedev_key_event(mousedev, code, value);
+		}
+		break;
 
-		case EV_KEY:
-			if (value != 2) {
-				if (code == BTN_TOUCH && test_bit(BTN_TOOL_FINGER, handle->dev->keybit))
-					mousedev_touchpad_touch(mousedev, value);
-				else
-					mousedev_key_event(mousedev, code, value);
+	case EV_SYN:
+		if (code == SYN_REPORT) {
+			if (mousedev->touch) {
+				mousedev->pkt_count++;
+				/*
+				 * Input system eats duplicate events,
+				 * but we need all of them to do correct
+				 * averaging so apply present one forward
+				 */
+				fx(0) = fx(1);
+				fy(0) = fy(1);
 			}
-			break;
-
-		case EV_SYN:
-			if (code == SYN_REPORT) {
-				if (mousedev->touch) {
-					mousedev->pkt_count++;
-					/* Input system eats duplicate events, but we need all of them
-					 * to do correct averaging so apply present one forward
-					 */
-					fx(0) = fx(1);
-					fy(0) = fy(1);
-				}
 
-				mousedev_notify_readers(mousedev, &mousedev->packet);
-				mousedev_notify_readers(mousedev_mix, &mousedev->packet);
+			mousedev_notify_readers(mousedev, &mousedev->packet);
+			mousedev_notify_readers(mousedev_mix, &mousedev->packet);
 
-				mousedev->packet.dx = mousedev->packet.dy = mousedev->packet.dz = 0;
-				mousedev->packet.abs_event = 0;
-			}
-			break;
+			mousedev->packet.dx = mousedev->packet.dy =
+				mousedev->packet.dz = 0;
+			mousedev->packet.abs_event = 0;
+		}
+		break;
 	}
 }
 
@@ -367,41 +413,45 @@ static void mousedev_free(struct device 
 {
 	struct mousedev *mousedev = container_of(dev, struct mousedev, dev);
 
-	mousedev_table[mousedev->minor] = NULL;
 	kfree(mousedev);
 }
 
-static int mixdev_add_device(struct mousedev *mousedev)
+static int mousedev_open_device(struct mousedev *mousedev)
 {
-	int error;
-
-	if (mousedev_mix->open) {
-		error = input_open_device(&mousedev->handle);
-		if (error)
-			return error;
+	int retval;
 
-		mousedev->open++;
-		mousedev->mixdev_open = 1;
-	}
+	retval = mutex_lock_interruptible(&mousedev->mutex);
+	if (retval)
+		return retval;
 
-	get_device(&mousedev->dev);
-	list_add_tail(&mousedev->mixdev_node, &mousedev_mix_list);
+	if (mousedev->minor == MOUSEDEV_MIX)
+		mixdev_open_devices();
+	else if (!mousedev->exist)
+		retval = -ENODEV;
+	else if (!mousedev->open++)
+		retval = input_open_device(&mousedev->handle);
 
-	return 0;
+	mutex_unlock(&mousedev->mutex);
+	return retval;
 }
 
-static void mixdev_remove_device(struct mousedev *mousedev)
+static void mousedev_close_device(struct mousedev *mousedev)
 {
-	if (mousedev->mixdev_open) {
-		mousedev->mixdev_open = 0;
-		if (!--mousedev->open && mousedev->exist)
-			input_close_device(&mousedev->handle);
-	}
+	mutex_lock(&mousedev->mutex);
 
-	list_del_init(&mousedev->mixdev_node);
-	put_device(&mousedev->dev);
+	if (mousedev->minor == MOUSEDEV_MIX)
+		mixdev_close_devices();
+	else if (mousedev->exist && !--mousedev->open)
+		input_close_device(&mousedev->handle);
+
+	mutex_unlock(&mousedev->mutex);
 }
 
+/*
+ * Open all available devices so they can all be multiplexed in one.
+ * stream. Note that this function is called with mousedev_mix->mutex
+ * held.
+ */
 static void mixdev_open_devices(void)
 {
 	struct mousedev *mousedev;
@@ -411,16 +461,19 @@ static void mixdev_open_devices(void)
 
 	list_for_each_entry(mousedev, &mousedev_mix_list, mixdev_node) {
 		if (!mousedev->mixdev_open) {
-			if (!mousedev->open && mousedev->exist)
-				if (input_open_device(&mousedev->handle))
-					continue;
+			if (mousedev_open_device(mousedev));
+				continue;
 
-			mousedev->open++;
 			mousedev->mixdev_open = 1;
 		}
 	}
 }
 
+/*
+ * Close all devices that were opened as part of multiplexed
+ * device. Note that this function is called with mousedev_mix->mutex
+ * held.
+ */
 static void mixdev_close_devices(void)
 {
 	struct mousedev *mousedev;
@@ -431,33 +484,50 @@ static void mixdev_close_devices(void)
 	list_for_each_entry(mousedev, &mousedev_mix_list, mixdev_node) {
 		if (mousedev->mixdev_open) {
 			mousedev->mixdev_open = 0;
-			if (!--mousedev->open && mousedev->exist)
-				input_close_device(&mousedev->handle);
+			mousedev_close_device(mousedev);
 		}
 	}
 }
 
+
+static void mousedev_attach_client(struct mousedev *mousedev,
+				   struct mousedev_client *client)
+{
+	spin_lock(&mousedev->client_lock);
+	list_add_tail_rcu(&client->node, &mousedev->client_list);
+	spin_unlock(&mousedev->client_lock);
+	/*
+	 * We don't use synchronize_rcu() here because read-size
+	 * critical section is protected by a spinlock (dev->event_lock)
+	 * instead of rcu_read_lock().
+	 */
+	synchronize_sched();
+}
+
+static void mousedev_detach_client(struct mousedev *mousedev,
+				   struct mousedev_client *client)
+{
+	spin_lock(&mousedev->client_lock);
+	list_del_rcu(&client->node);
+	spin_unlock(&mousedev->client_lock);
+	synchronize_sched();
+}
+
 static int mousedev_release(struct inode *inode, struct file *file)
 {
 	struct mousedev_client *client = file->private_data;
 	struct mousedev *mousedev = client->mousedev;
 
 	mousedev_fasync(-1, file, 0);
-
-	list_del(&client->node);
+	mousedev_detach_client(mousedev, client);
 	kfree(client);
 
-	if (mousedev->minor == MOUSEDEV_MIX)
-		mixdev_close_devices();
-	else if (!--mousedev->open && mousedev->exist)
-		input_close_device(&mousedev->handle);
-
+	mousedev_close_device(mousedev);
 	put_device(&mousedev->dev);
 
 	return 0;
 }
 
-
 static int mousedev_open(struct inode *inode, struct file *file)
 {
 	struct mousedev_client *client;
@@ -475,12 +545,17 @@ static int mousedev_open(struct inode *i
 	if (i >= MOUSEDEV_MINORS)
 		return -ENODEV;
 
+	error = mutex_lock_interruptible(&mousedev_table_mutex);
+	if (error)
+		return error;
 	mousedev = mousedev_table[i];
+	if (mousedev)
+		get_device(&mousedev->dev);
+	mutex_unlock(&mousedev_table_mutex);
+
 	if (!mousedev)
 		return -ENODEV;
 
-	get_device(&mousedev->dev);
-
 	client = kzalloc(sizeof(struct mousedev_client), GFP_KERNEL);
 	if (!client) {
 		error = -ENOMEM;
@@ -491,21 +566,17 @@ static int mousedev_open(struct inode *i
 	client->pos_x = xres / 2;
 	client->pos_y = yres / 2;
 	client->mousedev = mousedev;
-	list_add_tail(&client->node, &mousedev->client_list);
+	mousedev_attach_client(mousedev, client);
 
-	if (mousedev->minor == MOUSEDEV_MIX)
-		mixdev_open_devices();
-	else if (!mousedev->open++ && mousedev->exist) {
-		error = input_open_device(&mousedev->handle);
-		if (error)
-			goto err_free_client;
-	}
+	error = mousedev_open_device(mousedev);
+	if (error)
+		goto err_free_client;
 
 	file->private_data = client;
 	return 0;
 
  err_free_client:
-	list_del(&client->node);
+	mousedev_detach_client(mousedev, client);
 	kfree(client);
  err_put_mousedev:
 	put_device(&mousedev->dev);
@@ -517,41 +588,41 @@ static inline int mousedev_limit_delta(i
 	return delta > limit ? limit : (delta < -limit ? -limit : delta);
 }
 
-static void mousedev_packet(struct mousedev_client *client, signed char *ps2_data)
+static void mousedev_packet(struct mousedev_client *client,
+			    signed char *ps2_data)
 {
-	struct mousedev_motion *p;
-	unsigned long flags;
-
-	spin_lock_irqsave(&client->packet_lock, flags);
-	p = &client->packets[client->tail];
+	struct mousedev_motion *p = &client->packets[client->tail];
 
-	ps2_data[0] = 0x08 | ((p->dx < 0) << 4) | ((p->dy < 0) << 5) | (p->buttons & 0x07);
+	ps2_data[0] = 0x08 |
+		((p->dx < 0) << 4) | ((p->dy < 0) << 5) | (p->buttons & 0x07);
 	ps2_data[1] = mousedev_limit_delta(p->dx, 127);
 	ps2_data[2] = mousedev_limit_delta(p->dy, 127);
 	p->dx -= ps2_data[1];
 	p->dy -= ps2_data[2];
 
 	switch (client->mode) {
-		case MOUSEDEV_EMUL_EXPS:
-			ps2_data[3] = mousedev_limit_delta(p->dz, 7);
-			p->dz -= ps2_data[3];
-			ps2_data[3] = (ps2_data[3] & 0x0f) | ((p->buttons & 0x18) << 1);
-			client->bufsiz = 4;
-			break;
-
-		case MOUSEDEV_EMUL_IMPS:
-			ps2_data[0] |= ((p->buttons & 0x10) >> 3) | ((p->buttons & 0x08) >> 1);
-			ps2_data[3] = mousedev_limit_delta(p->dz, 127);
-			p->dz -= ps2_data[3];
-			client->bufsiz = 4;
-			break;
-
-		case MOUSEDEV_EMUL_PS2:
-		default:
-			ps2_data[0] |= ((p->buttons & 0x10) >> 3) | ((p->buttons & 0x08) >> 1);
-			p->dz = 0;
-			client->bufsiz = 3;
-			break;
+	case MOUSEDEV_EMUL_EXPS:
+		ps2_data[3] = mousedev_limit_delta(p->dz, 7);
+		p->dz -= ps2_data[3];
+		ps2_data[3] = (ps2_data[3] & 0x0f) | ((p->buttons & 0x18) << 1);
+		client->bufsiz = 4;
+		break;
+
+	case MOUSEDEV_EMUL_IMPS:
+		ps2_data[0] |=
+			((p->buttons & 0x10) >> 3) | ((p->buttons & 0x08) >> 1);
+		ps2_data[3] = mousedev_limit_delta(p->dz, 127);
+		p->dz -= ps2_data[3];
+		client->bufsiz = 4;
+		break;
+
+	case MOUSEDEV_EMUL_PS2:
+	default:
+		ps2_data[0] |=
+			((p->buttons & 0x10) >> 3) | ((p->buttons & 0x08) >> 1);
+		p->dz = 0;
+		client->bufsiz = 3;
+		break;
 	}
 
 	if (!p->dx && !p->dy && !p->dz) {
@@ -561,12 +632,50 @@ static void mousedev_packet(struct mouse
 		} else
 			client->tail = (client->tail + 1) % PACKET_QUEUE_LEN;
 	}
-
-	spin_unlock_irqrestore(&client->packet_lock, flags);
 }
 
+static void mousedev_generate_response(struct mousedev_client *client,
+					int command)
+{
+	client->ps2[0] = 0xfa; /* ACK */
+
+	switch (command) {
+
+	case 0xeb: /* Poll */
+		mousedev_packet(client, &client->ps2[1]);
+		client->bufsiz++; /* account for leading ACK */
+		break;
+
+	case 0xf2: /* Get ID */
+		switch (client->mode) {
+			case MOUSEDEV_EMUL_PS2:  client->ps2[1] = 0; break;
+			case MOUSEDEV_EMUL_IMPS: client->ps2[1] = 3; break;
+			case MOUSEDEV_EMUL_EXPS: client->ps2[1] = 4; break;
+		}
+		client->bufsiz = 2;
+		break;
+
+	case 0xe9: /* Get info */
+		client->ps2[1] = 0x60; client->ps2[2] = 3; client->ps2[3] = 200;
+		client->bufsiz = 4;
+		break;
+
+	case 0xff: /* Reset */
+		client->impsseq = client->imexseq = 0;
+		client->mode = MOUSEDEV_EMUL_PS2;
+		client->ps2[1] = 0xaa; client->ps2[2] = 0x00;
+		client->bufsiz = 3;
+		break;
+
+	default:
+		client->bufsiz = 1;
+		break;
+	}
+	client->buffer = client->bufsiz;
+}
 
-static ssize_t mousedev_write(struct file *file, const char __user *buffer, size_t count, loff_t *ppos)
+static ssize_t mousedev_write(struct file *file, const char __user *buffer,
+				size_t count, loff_t *ppos)
 {
 	struct mousedev_client *client = file->private_data;
 	unsigned char c;
@@ -577,6 +686,8 @@ static ssize_t mousedev_write(struct fil
 		if (get_user(c, buffer + i))
 			return -EFAULT;
 
+		spin_lock_irq(&client->packet_lock);
+
 		if (c == mousedev_imex_seq[client->imexseq]) {
 			if (++client->imexseq == MOUSEDEV_SEQ_LEN) {
 				client->imexseq = 0;
@@ -593,68 +704,39 @@ static ssize_t mousedev_write(struct fil
 		} else
 			client->impsseq = 0;
 
-		client->ps2[0] = 0xfa;
-
-		switch (c) {
+		mousedev_generate_response(client, c);
 
-			case 0xeb: /* Poll */
-				mousedev_packet(client, &client->ps2[1]);
-				client->bufsiz++; /* account for leading ACK */
-				break;
-
-			case 0xf2: /* Get ID */
-				switch (client->mode) {
-					case MOUSEDEV_EMUL_PS2:  client->ps2[1] = 0; break;
-					case MOUSEDEV_EMUL_IMPS: client->ps2[1] = 3; break;
-					case MOUSEDEV_EMUL_EXPS: client->ps2[1] = 4; break;
-				}
-				client->bufsiz = 2;
-				break;
-
-			case 0xe9: /* Get info */
-				client->ps2[1] = 0x60; client->ps2[2] = 3; client->ps2[3] = 200;
-				client->bufsiz = 4;
-				break;
-
-			case 0xff: /* Reset */
-				client->impsseq = client->imexseq = 0;
-				client->mode = MOUSEDEV_EMUL_PS2;
-				client->ps2[1] = 0xaa; client->ps2[2] = 0x00;
-				client->bufsiz = 3;
-				break;
-
-			default:
-				client->bufsiz = 1;
-				break;
-		}
-
-		client->buffer = client->bufsiz;
+		spin_unlock_irq(&client->packet_lock);
 	}
 
 	kill_fasync(&client->fasync, SIGIO, POLL_IN);
-
 	wake_up_interruptible(&client->mousedev->wait);
 
 	return count;
 }
 
-static ssize_t mousedev_read(struct file *file, char __user *buffer, size_t count, loff_t *ppos)
+static ssize_t mousedev_read(struct file *file, char __user *buffer,
+			     size_t count, loff_t *ppos)
 {
 	struct mousedev_client *client = file->private_data;
+	struct mousedev *mousedev = client->mousedev;
+	signed char data[sizeof(client->ps2)];
 	int retval = 0;
 
-	if (!client->ready && !client->buffer && (file->f_flags & O_NONBLOCK))
+	if (!client->ready && !client->buffer && mousedev->exist &&
+	    (file->f_flags & O_NONBLOCK))
 		return -EAGAIN;
 
-	retval = wait_event_interruptible(client->mousedev->wait,
-					  !client->mousedev->exist || client->ready || client->buffer);
-
+	retval = wait_event_interruptible(mousedev->wait,
+			!mousedev->exist || client->ready || client->buffer);
 	if (retval)
 		return retval;
 
-	if (!client->mousedev->exist)
+	if (!mousedev->exist)
 		return -ENODEV;
 
+	spin_lock_irq(&client->packet_lock);
+
 	if (!client->buffer && client->ready) {
 		mousedev_packet(client, client->ps2);
 		client->buffer = client->bufsiz;
@@ -663,9 +745,12 @@ static ssize_t mousedev_read(struct file
 	if (count > client->buffer)
 		count = client->buffer;
 
+	memcpy(data, client->ps2 + client->bufsiz - client->buffer, count);
 	client->buffer -= count;
 
-	if (copy_to_user(buffer, client->ps2 + client->bufsiz - client->buffer - count, count))
+	spin_unlock_irq(&client->packet_lock);
+
+	if (copy_to_user(buffer, data, count))
 		return -EFAULT;
 
 	return count;
@@ -692,6 +777,60 @@ static const struct file_operations mous
 	.fasync =	mousedev_fasync,
 };
 
+static int mousedev_install_chrdev(struct mousedev *mousedev)
+{
+	mousedev_table[mousedev->minor] = mousedev;
+	return 0;
+}
+
+static void mousedev_remove_chrdev(struct mousedev *mousedev)
+{
+	mutex_lock(&mousedev_table_mutex);
+	mousedev_table[mousedev->minor] = NULL;
+	mutex_unlock(&mousedev_table_mutex);
+}
+
+/*
+ * Mark device non-existent. This disables writes, ioctls and
+ * prevents new users from opening the device. Already posted
+ * blocking reads will stay, however new ones will fail.
+ */
+static void mousedev_mark_dead(struct mousedev *mousedev)
+{
+	mutex_lock(&mousedev->mutex);
+	mousedev->exist = 0;
+	mutex_unlock(&mousedev->mutex);
+}
+
+/*
+ * Wake up users waiting for IO so they can disconnect from
+ * dead device.
+ */
+static void mousedev_hangup(struct mousedev *mousedev)
+{
+	struct mousedev_client *client;
+
+	spin_lock(&mousedev->client_lock);
+	list_for_each_entry(client, &mousedev->client_list, node)
+		kill_fasync(&client->fasync, SIGIO, POLL_HUP);
+	spin_unlock(&mousedev->client_lock);
+
+	wake_up_interruptible(&mousedev->wait);
+}
+
+static void mousedev_cleanup(struct mousedev *mousedev)
+{
+	struct input_handle *handle = &mousedev->handle;
+
+	mousedev_mark_dead(mousedev);
+	mousedev_hangup(mousedev);
+	mousedev_remove_chrdev(mousedev);
+
+	/* mousedev is marked dead so no one else accesses mousedev->open */
+	if (mousedev->open)
+		input_close_device(handle);
+}
+
 static struct mousedev *mousedev_create(struct input_dev *dev,
 					struct input_handler *handler,
 					int minor)
@@ -707,6 +846,10 @@ static struct mousedev *mousedev_create(
 
 	INIT_LIST_HEAD(&mousedev->client_list);
 	INIT_LIST_HEAD(&mousedev->mixdev_node);
+	spin_lock_init(&mousedev->client_lock);
+	mutex_init(&mousedev->mutex);
+	lockdep_set_subclass(&mousedev->mutex,
+			     minor == MOUSEDEV_MIX ? MOUSEDEV_MIX : 0);
 	init_waitqueue_head(&mousedev->wait);
 
 	if (minor == MOUSEDEV_MIX)
@@ -731,14 +874,27 @@ static struct mousedev *mousedev_create(
 	mousedev->dev.release = mousedev_free;
 	device_initialize(&mousedev->dev);
 
-	mousedev_table[minor] = mousedev;
+	if (minor != MOUSEDEV_MIX) {
+		error = input_register_handle(&mousedev->handle);
+		if (error)
+			goto err_free_mousedev;
+	}
+
+	error = mousedev_install_chrdev(mousedev);
+	if (error)
+		goto err_unregister_handle;
 
 	error = device_add(&mousedev->dev);
 	if (error)
-		goto err_free_mousedev;
+		goto err_cleanup_mousedev;
 
 	return mousedev;
 
+ err_cleanup_mousedev:
+	mousedev_cleanup(mousedev);
+ err_unregister_handle:
+	if (minor != MOUSEDEV_MIX)
+		input_unregister_handle(&mousedev->handle);
  err_free_mousedev:
 	put_device(&mousedev->dev);
  err_out:
@@ -747,29 +903,64 @@ static struct mousedev *mousedev_create(
 
 static void mousedev_destroy(struct mousedev *mousedev)
 {
-	struct mousedev_client *client;
-
 	device_del(&mousedev->dev);
-	mousedev->exist = 0;
+	mousedev_cleanup(mousedev);
+	if (mousedev->minor != MOUSEDEV_MIX)
+		input_unregister_handle(&mousedev->handle);
+	put_device(&mousedev->dev);
+}
 
-	if (mousedev->open) {
-		input_close_device(&mousedev->handle);
-		list_for_each_entry(client, &mousedev->client_list, node)
-			kill_fasync(&client->fasync, SIGIO, POLL_HUP);
-		wake_up_interruptible(&mousedev->wait);
+static int mixdev_add_device(struct mousedev *mousedev)
+{
+	int retval;
+
+	retval = mutex_lock_interruptible(&mousedev_mix->mutex);
+	if (retval)
+		return retval;
+
+	if (mousedev_mix->open) {
+		retval = mousedev_open_device(mousedev);
+		if (retval)
+			goto out;
+
+		mousedev->mixdev_open = 1;
+	}
+
+	get_device(&mousedev->dev);
+	list_add_tail(&mousedev->mixdev_node, &mousedev_mix_list);
+
+ out:
+	mutex_unlock(&mousedev_mix->mutex);
+	return retval;
+}
+
+static void mixdev_remove_device(struct mousedev *mousedev)
+{
+	mutex_lock(&mousedev_mix->mutex);
+
+	if (mousedev->mixdev_open) {
+		mousedev->mixdev_open = 0;
+		mousedev_close_device(mousedev);
 	}
 
+	list_del_init(&mousedev->mixdev_node);
+	mutex_unlock(&mousedev_mix->mutex);
+
 	put_device(&mousedev->dev);
 }
 
-static int mousedev_connect(struct input_handler *handler, struct input_dev *dev,
+static int mousedev_connect(struct input_handler *handler,
+			    struct input_dev *dev,
 			    const struct input_device_id *id)
 {
 	struct mousedev *mousedev;
 	int minor;
 	int error;
 
-	for (minor = 0; minor < MOUSEDEV_MINORS && mousedev_table[minor]; minor++);
+	for (minor = 0; minor < MOUSEDEV_MINORS; minor++)
+		if (!mousedev_table[minor])
+			break;
+
 	if (minor == MOUSEDEV_MINORS) {
 		printk(KERN_ERR "mousedev: no more free mousedev devices\n");
 		return -ENFILE;
@@ -779,21 +970,13 @@ static int mousedev_connect(struct input
 	if (IS_ERR(mousedev))
 		return PTR_ERR(mousedev);
 
-	error = input_register_handle(&mousedev->handle);
-	if (error)
-		goto err_delete_mousedev;
-
 	error = mixdev_add_device(mousedev);
-	if (error)
-		goto err_unregister_handle;
+	if (error) {
+		mousedev_destroy(mousedev);
+		return error;
+	}
 
 	return 0;
-
- err_unregister_handle:
-	input_unregister_handle(&mousedev->handle);
- err_delete_mousedev:
-	device_unregister(&mousedev->dev);
-	return error;
 }
 
 static void mousedev_disconnect(struct input_handle *handle)
@@ -801,33 +984,42 @@ static void mousedev_disconnect(struct i
 	struct mousedev *mousedev = handle->private;
 
 	mixdev_remove_device(mousedev);
-	input_unregister_handle(handle);
 	mousedev_destroy(mousedev);
 }
 
 static const struct input_device_id mousedev_ids[] = {
 	{
-		.flags = INPUT_DEVICE_ID_MATCH_EVBIT | INPUT_DEVICE_ID_MATCH_KEYBIT | INPUT_DEVICE_ID_MATCH_RELBIT,
+		.flags = INPUT_DEVICE_ID_MATCH_EVBIT |
+				INPUT_DEVICE_ID_MATCH_KEYBIT |
+				INPUT_DEVICE_ID_MATCH_RELBIT,
 		.evbit = { BIT(EV_KEY) | BIT(EV_REL) },
 		.keybit = { [LONG(BTN_LEFT)] = BIT(BTN_LEFT) },
 		.relbit = { BIT(REL_X) | BIT(REL_Y) },
-	},	/* A mouse like device, at least one button, two relative axes */
+	},	/* A mouse like device, at least one button,
+		   two relative axes */
 	{
-		.flags = INPUT_DEVICE_ID_MATCH_EVBIT | INPUT_DEVICE_ID_MATCH_RELBIT,
+		.flags = INPUT_DEVICE_ID_MATCH_EVBIT |
+				INPUT_DEVICE_ID_MATCH_RELBIT,
 		.evbit = { BIT(EV_KEY) | BIT(EV_REL) },
 		.relbit = { BIT(REL_WHEEL) },
 	},	/* A separate scrollwheel */
 	{
-		.flags = INPUT_DEVICE_ID_MATCH_EVBIT | INPUT_DEVICE_ID_MATCH_KEYBIT | INPUT_DEVICE_ID_MATCH_ABSBIT,
+		.flags = INPUT_DEVICE_ID_MATCH_EVBIT |
+				INPUT_DEVICE_ID_MATCH_KEYBIT |
+				INPUT_DEVICE_ID_MATCH_ABSBIT,
 		.evbit = { BIT(EV_KEY) | BIT(EV_ABS) },
 		.keybit = { [LONG(BTN_TOUCH)] = BIT(BTN_TOUCH) },
 		.absbit = { BIT(ABS_X) | BIT(ABS_Y) },
-	},	/* A tablet like device, at least touch detection, two absolute axes */
+	},	/* A tablet like device, at least touch detection,
+		   two absolute axes */
 	{
-		.flags = INPUT_DEVICE_ID_MATCH_EVBIT | INPUT_DEVICE_ID_MATCH_KEYBIT | INPUT_DEVICE_ID_MATCH_ABSBIT,
+		.flags = INPUT_DEVICE_ID_MATCH_EVBIT |
+				INPUT_DEVICE_ID_MATCH_KEYBIT |
+				INPUT_DEVICE_ID_MATCH_ABSBIT,
 		.evbit = { BIT(EV_KEY) | BIT(EV_ABS) },
 		.keybit = { [LONG(BTN_TOOL_FINGER)] = BIT(BTN_TOOL_FINGER) },
-		.absbit = { BIT(ABS_X) | BIT(ABS_Y) | BIT(ABS_PRESSURE) | BIT(ABS_TOOL_WIDTH) },
+		.absbit = { BIT(ABS_X) | BIT(ABS_Y) | BIT(ABS_PRESSURE) |
+				BIT(ABS_TOOL_WIDTH) },
 	},	/* A touchpad */
 
 	{ },	/* Terminating entry */