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

[Dmitry Torokhov <dtor@insightbb.com>]

[-- Attachment #1: joydev-locking.patch --]
[-- Type: text/plain, Size: 28880 bytes --]

Input: joydev - implement proper locking

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

 drivers/input/joydev.c |  745 ++++++++++++++++++++++++++++++++-----------------
 1 files changed, 493 insertions(+), 252 deletions(-)

Index: work/drivers/input/joydev.c
===================================================================
--- work.orig/drivers/input/joydev.c
+++ work/drivers/input/joydev.c
@@ -43,6 +43,8 @@ struct joydev {
 	struct input_handle handle;
 	wait_queue_head_t wait;
 	struct list_head client_list;
+	spinlock_t client_lock; /* protects client_list */
+	struct mutex mutex;
 	struct device dev;
 
 	struct js_corr corr[ABS_MAX + 1];
@@ -61,31 +63,61 @@ struct joydev_client {
 	int head;
 	int tail;
 	int startup;
+	spinlock_t buffer_lock; /* protects access to buffer, head and tail */
 	struct fasync_struct *fasync;
 	struct joydev *joydev;
 	struct list_head node;
 };
 
 static struct joydev *joydev_table[JOYDEV_MINORS];
+static DEFINE_MUTEX(joydev_table_mutex);
 
 static int joydev_correct(int value, struct js_corr *corr)
 {
 	switch (corr->type) {
-		case JS_CORR_NONE:
-			break;
-		case JS_CORR_BROKEN:
-			value = value > corr->coef[0] ? (value < corr->coef[1] ? 0 :
-				((corr->coef[3] * (value - corr->coef[1])) >> 14)) :
-				((corr->coef[2] * (value - corr->coef[0])) >> 14);
-			break;
-		default:
-			return 0;
+
+	case JS_CORR_NONE:
+		break;
+
+	case JS_CORR_BROKEN:
+		value = value > corr->coef[0] ? (value < corr->coef[1] ? 0 :
+			((corr->coef[3] * (value - corr->coef[1])) >> 14)) :
+			((corr->coef[2] * (value - corr->coef[0])) >> 14);
+		break;
+
+	default:
+		return 0;
 	}
 
 	return value < -32767 ? -32767 : (value > 32767 ? 32767 : value);
 }
 
-static void joydev_event(struct input_handle *handle, unsigned int type, unsigned int code, int value)
+static void joydev_pass_event(struct joydev_client *client,
+			      struct js_event *event)
+{
+	struct joydev *joydev = client->joydev;
+
+	/*
+	 * IRQs already disabled, just acquire the lock
+	 */
+	spin_lock(&client->buffer_lock);
+
+	client->buffer[client->head] = *event;
+
+	if (client->startup == joydev->nabs + joydev->nkey) {
+		client->head++;
+		client->head &= JOYDEV_BUFFER_SIZE - 1;
+		if (client->tail == client->head)
+			client->startup = 0;
+	}
+
+	spin_unlock(&client->buffer_lock);
+
+	kill_fasync(&client->fasync, SIGIO, POLL_IN);
+}
+
+static void joydev_event(struct input_handle *handle,
+			 unsigned int type, unsigned int code, int value)
 {
 	struct joydev *joydev = handle->private;
 	struct joydev_client *client;
@@ -93,39 +125,32 @@ static void joydev_event(struct input_ha
 
 	switch (type) {
 
-		case EV_KEY:
-			if (code < BTN_MISC || value == 2)
-				return;
-			event.type = JS_EVENT_BUTTON;
-			event.number = joydev->keymap[code - BTN_MISC];
-			event.value = value;
-			break;
-
-		case EV_ABS:
-			event.type = JS_EVENT_AXIS;
-			event.number = joydev->absmap[code];
-			event.value = joydev_correct(value, joydev->corr + event.number);
-			if (event.value == joydev->abs[event.number])
-				return;
-			joydev->abs[event.number] = event.value;
-			break;
+	case EV_KEY:
+		if (code < BTN_MISC || value == 2)
+			return;
+		event.type = JS_EVENT_BUTTON;
+		event.number = joydev->keymap[code - BTN_MISC];
+		event.value = value;
+		break;
 
-		default:
+	case EV_ABS:
+		event.type = JS_EVENT_AXIS;
+		event.number = joydev->absmap[code];
+		event.value = joydev_correct(value,
+					&joydev->corr[event.number]);
+		if (event.value == joydev->abs[event.number])
 			return;
+		joydev->abs[event.number] = event.value;
+		break;
+
+	default:
+		return;
 	}
 
 	event.time = jiffies_to_msecs(jiffies);
 
-	list_for_each_entry(client, &joydev->client_list, node) {
-
-		memcpy(client->buffer + client->head, &event, sizeof(struct js_event));
-
-		if (client->startup == joydev->nabs + joydev->nkey)
-			if (client->tail == (client->head = (client->head + 1) & (JOYDEV_BUFFER_SIZE - 1)))
-				client->startup = 0;
-
-		kill_fasync(&client->fasync, SIGIO, POLL_IN);
-	}
+	list_for_each_entry_rcu(client, &joydev->client_list, node)
+		joydev_pass_event(client, &event);
 
 	wake_up_interruptible(&joydev->wait);
 }
@@ -144,23 +169,85 @@ static void joydev_free(struct device *d
 {
 	struct joydev *joydev = container_of(dev, struct joydev, dev);
 
-	joydev_table[joydev->minor] = NULL;
 	kfree(joydev);
 }
 
+static void joydev_attach_client(struct joydev *joydev,
+				 struct joydev_client *client)
+{
+	spin_lock(&joydev->client_lock);
+	list_add_tail_rcu(&client->node, &joydev->client_list);
+	spin_unlock(&joydev->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 joydev_detach_client(struct joydev *joydev,
+				 struct joydev_client *client)
+{
+	spin_lock(&joydev->client_lock);
+	list_del_rcu(&client->node);
+	spin_unlock(&joydev->client_lock);
+	synchronize_sched();
+}
+
+static int joydev_open_device(struct joydev *joydev)
+{
+	int retval;
+
+	retval = mutex_lock_interruptible(&joydev->mutex);
+	if (retval)
+		return retval;
+
+	if (!joydev->exist)
+		retval = -ENODEV;
+	else if (!joydev->open++)
+		retval = input_open_device(&joydev->handle);
+
+	mutex_unlock(&joydev->mutex);
+	return retval;
+}
+
+static void joydev_close_device(struct joydev *joydev)
+{
+	mutex_lock(&joydev->mutex);
+
+	if (joydev->exist && !--joydev->open)
+		input_close_device(&joydev->handle);
+
+	mutex_unlock(&joydev->mutex);
+}
+
+/*
+ * Wake up users waiting for IO so they can disconnect from
+ * dead device.
+ */
+static void joydev_hangup(struct joydev *joydev)
+{
+	struct joydev_client *client;
+
+	spin_lock(&joydev->client_lock);
+	list_for_each_entry(client, &joydev->client_list, node)
+		kill_fasync(&client->fasync, SIGIO, POLL_HUP);
+	spin_unlock(&joydev->client_lock);
+
+	wake_up_interruptible(&joydev->wait);
+}
+
 static int joydev_release(struct inode *inode, struct file *file)
 {
 	struct joydev_client *client = file->private_data;
 	struct joydev *joydev = client->joydev;
 
 	joydev_fasync(-1, file, 0);
-
-	list_del(&client->node);
+	joydev_detach_client(joydev, client);
 	kfree(client);
 
-	if (!--joydev->open && joydev->exist)
-		input_close_device(&joydev->handle);
-
+	joydev_close_device(joydev);
 	put_device(&joydev->dev);
 
 	return 0;
@@ -176,11 +263,16 @@ static int joydev_open(struct inode *ino
 	if (i >= JOYDEV_MINORS)
 		return -ENODEV;
 
+	error = mutex_lock_interruptible(&joydev_table_mutex);
+	if (error)
+		return error;
 	joydev = joydev_table[i];
-	if (!joydev || !joydev->exist)
-		return -ENODEV;
+	if (joydev)
+		get_device(&joydev->dev);
+	mutex_unlock(&joydev_table_mutex);
 
-	get_device(&joydev->dev);
+	if (!joydev)
+		return -ENODEV;
 
 	client = kzalloc(sizeof(struct joydev_client), GFP_KERNEL);
 	if (!client) {
@@ -188,37 +280,129 @@ static int joydev_open(struct inode *ino
 		goto err_put_joydev;
 	}
 
+	spin_lock_init(&client->buffer_lock);
 	client->joydev = joydev;
-	list_add_tail(&client->node, &joydev->client_list);
+	joydev_attach_client(joydev, client);
 
-	if (!joydev->open++ && joydev->exist) {
-		error = input_open_device(&joydev->handle);
-		if (error)
-			goto err_free_client;
-	}
+	error = joydev_open_device(joydev);
+	if (error)
+		goto err_free_client;
 
 	file->private_data = client;
 	return 0;
 
  err_free_client:
-	list_del(&client->node);
+	joydev_detach_client(joydev, client);
 	kfree(client);
  err_put_joydev:
 	put_device(&joydev->dev);
 	return error;
 }
 
-static ssize_t joydev_write(struct file *file, const char __user *buffer, size_t count, loff_t *ppos)
+static int joydev_generate_startup_event(struct joydev_client *client,
+					 struct input_dev *input,
+					 struct js_event *event)
 {
-	return -EINVAL;
+	struct joydev *joydev = client->joydev;
+	int have_event;
+
+	spin_lock_irq(&client->buffer_lock);
+
+	have_event = client->startup < joydev->nabs + joydev->nkey;
+
+	if (have_event) {
+
+		event->time = jiffies_to_msecs(jiffies);
+		if (client->startup < joydev->nkey) {
+			event->type = JS_EVENT_BUTTON | JS_EVENT_INIT;
+			event->number = client->startup;
+			event->value = !!test_bit(joydev->keypam[event->number],
+						  input->key);
+		} else {
+			event->type = JS_EVENT_AXIS | JS_EVENT_INIT;
+			event->number = client->startup - joydev->nkey;
+			event->value = joydev->abs[event->number];
+		}
+		client->startup++;
+	}
+
+	spin_unlock_irq(&client->buffer_lock);
+
+	return have_event;
+}
+
+static int joydev_fetch_next_event(struct joydev_client *client,
+				   struct js_event *event)
+{
+	int have_event;
+
+	spin_lock_irq(&client->buffer_lock);
+
+	have_event = client->head != client->tail;
+	if (have_event) {
+		*event = client->buffer[client->tail++];
+		client->tail &= JOYDEV_BUFFER_SIZE - 1;
+	}
+
+	spin_unlock_irq(&client->buffer_lock);
+
+	return have_event;
 }
 
-static ssize_t joydev_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
+/*
+ * Old joystick interface
+ */
+static ssize_t joydev_0x_read(struct joydev_client *client,
+			      struct input_dev *input,
+			      char __user *buf)
+{
+	struct joydev *joydev = client->joydev;
+	struct JS_DATA_TYPE data;
+	int i;
+
+	spin_lock_irq(&input->event_lock);
+
+	/*
+	 * Get device state
+	 */
+	for (data.buttons = i = 0; i < 32 && i < joydev->nkey; i++)
+		data.buttons |=
+			test_bit(joydev->keypam[i], input->key) ? (1 << i) : 0;
+	data.x = (joydev->abs[0] / 256 + 128) >> joydev->glue.JS_CORR.x;
+	data.y = (joydev->abs[1] / 256 + 128) >> joydev->glue.JS_CORR.y;
+
+	/*
+	 * Reset reader's event queue
+	 */
+	spin_lock(&client->buffer_lock);
+	client->startup = 0;
+	client->tail = client->head;
+	spin_unlock(&client->buffer_lock);
+
+	spin_unlock_irq(&input->event_lock);
+
+	if (copy_to_user(buf, &data, sizeof(struct JS_DATA_TYPE)))
+		return -EFAULT;
+
+	return sizeof(struct JS_DATA_TYPE);
+}
+
+static inline int joydev_data_pending(struct joydev_client *client)
+{
+	struct joydev *joydev = client->joydev;
+
+	return client->startup < joydev->nabs + joydev->nkey ||
+		client->head != client->tail;
+}
+
+static ssize_t joydev_read(struct file *file, char __user *buf,
+			   size_t count, loff_t *ppos)
 {
 	struct joydev_client *client = file->private_data;
 	struct joydev *joydev = client->joydev;
 	struct input_dev *input = joydev->handle.dev;
-	int retval = 0;
+	struct js_event event;
+	int retval;
 
 	if (!joydev->exist)
 		return -ENODEV;
@@ -226,68 +410,35 @@ static ssize_t joydev_read(struct file *
 	if (count < sizeof(struct js_event))
 		return -EINVAL;
 
-	if (count == sizeof(struct JS_DATA_TYPE)) {
-
-		struct JS_DATA_TYPE data;
-		int i;
-
-		for (data.buttons = i = 0; i < 32 && i < joydev->nkey; i++)
-			data.buttons |= test_bit(joydev->keypam[i], input->key) ? (1 << i) : 0;
-		data.x = (joydev->abs[0] / 256 + 128) >> joydev->glue.JS_CORR.x;
-		data.y = (joydev->abs[1] / 256 + 128) >> joydev->glue.JS_CORR.y;
-
-		if (copy_to_user(buf, &data, sizeof(struct JS_DATA_TYPE)))
-			return -EFAULT;
-
-		client->startup = 0;
-		client->tail = client->head;
-
-		return sizeof(struct JS_DATA_TYPE);
-	}
+	if (count == sizeof(struct JS_DATA_TYPE))
+		return joydev_0x_read(client, input, buf);
 
-	if (client->startup == joydev->nabs + joydev->nkey &&
-	    client->head == client->tail && (file->f_flags & O_NONBLOCK))
+	if (!joydev_data_pending(client) && (file->f_flags & O_NONBLOCK))
 		return -EAGAIN;
 
 	retval = wait_event_interruptible(joydev->wait,
-					  !joydev->exist ||
-					  client->startup < joydev->nabs + joydev->nkey ||
-					  client->head != client->tail);
+			!joydev->exist || joydev_data_pending(client));
 	if (retval)
 		return retval;
 
 	if (!joydev->exist)
 		return -ENODEV;
 
-	while (client->startup < joydev->nabs + joydev->nkey && retval + sizeof(struct js_event) <= count) {
-
-		struct js_event event;
-
-		event.time = jiffies_to_msecs(jiffies);
-
-		if (client->startup < joydev->nkey) {
-			event.type = JS_EVENT_BUTTON | JS_EVENT_INIT;
-			event.number = client->startup;
-			event.value = !!test_bit(joydev->keypam[event.number], input->key);
-		} else {
-			event.type = JS_EVENT_AXIS | JS_EVENT_INIT;
-			event.number = client->startup - joydev->nkey;
-			event.value = joydev->abs[event.number];
-		}
+	while (retval + sizeof(struct js_event) <= count &&
+	       joydev_generate_startup_event(client, input, &event)) {
 
 		if (copy_to_user(buf + retval, &event, sizeof(struct js_event)))
 			return -EFAULT;
 
-		client->startup++;
 		retval += sizeof(struct js_event);
 	}
 
-	while (client->head != client->tail && retval + sizeof(struct js_event) <= count) {
+	while (retval + sizeof(struct js_event) <= count &&
+	       joydev_fetch_next_event(client, &event)) {
 
-		if (copy_to_user(buf + retval, client->buffer + client->tail, sizeof(struct js_event)))
+		if (copy_to_user(buf + retval, &event, sizeof(struct js_event)))
 			return -EFAULT;
 
-		client->tail = (client->tail + 1) & (JOYDEV_BUFFER_SIZE - 1);
 		retval += sizeof(struct js_event);
 	}
 
@@ -301,126 +452,144 @@ static unsigned int joydev_poll(struct f
 	struct joydev *joydev = client->joydev;
 
 	poll_wait(file, &joydev->wait, wait);
-	return ((client->head != client->tail || client->startup < joydev->nabs + joydev->nkey) ?
-		(POLLIN | POLLRDNORM) : 0) | (joydev->exist ? 0 : (POLLHUP | POLLERR));
+	return (joydev_data_pending(client) ? (POLLIN | POLLRDNORM) : 0) |
+		(joydev->exist ?  0 : (POLLHUP | POLLERR));
 }
 
-static int joydev_ioctl_common(struct joydev *joydev, unsigned int cmd, void __user *argp)
+static int joydev_ioctl_common(struct joydev *joydev,
+				unsigned int cmd, void __user *argp)
 {
 	struct input_dev *dev = joydev->handle.dev;
 	int i, j;
 
 	switch (cmd) {
 
-		case JS_SET_CAL:
-			return copy_from_user(&joydev->glue.JS_CORR, argp,
+	case JS_SET_CAL:
+		return copy_from_user(&joydev->glue.JS_CORR, argp,
 				sizeof(joydev->glue.JS_CORR)) ? -EFAULT : 0;
 
-		case JS_GET_CAL:
-			return copy_to_user(argp, &joydev->glue.JS_CORR,
+	case JS_GET_CAL:
+		return copy_to_user(argp, &joydev->glue.JS_CORR,
 				sizeof(joydev->glue.JS_CORR)) ? -EFAULT : 0;
 
-		case JS_SET_TIMEOUT:
-			return get_user(joydev->glue.JS_TIMEOUT, (s32 __user *) argp);
+	case JS_SET_TIMEOUT:
+		return get_user(joydev->glue.JS_TIMEOUT, (s32 __user *) argp);
 
-		case JS_GET_TIMEOUT:
-			return put_user(joydev->glue.JS_TIMEOUT, (s32 __user *) argp);
+	case JS_GET_TIMEOUT:
+		return put_user(joydev->glue.JS_TIMEOUT, (s32 __user *) argp);
 
-		case JSIOCGVERSION:
-			return put_user(JS_VERSION, (__u32 __user *) argp);
+	case JSIOCGVERSION:
+		return put_user(JS_VERSION, (__u32 __user *) argp);
 
-		case JSIOCGAXES:
-			return put_user(joydev->nabs, (__u8 __user *) argp);
-
-		case JSIOCGBUTTONS:
-			return put_user(joydev->nkey, (__u8 __user *) argp);
-
-		case JSIOCSCORR:
-			if (copy_from_user(joydev->corr, argp,
-				      sizeof(joydev->corr[0]) * joydev->nabs))
-			    return -EFAULT;
-			for (i = 0; i < joydev->nabs; i++) {
-				j = joydev->abspam[i];
-			        joydev->abs[i] = joydev_correct(dev->abs[j], joydev->corr + i);
-			}
-			return 0;
-
-		case JSIOCGCORR:
-			return copy_to_user(argp, joydev->corr,
-						sizeof(joydev->corr[0]) * joydev->nabs) ? -EFAULT : 0;
+	case JSIOCGAXES:
+		return put_user(joydev->nabs, (__u8 __user *) argp);
+
+	case JSIOCGBUTTONS:
+		return put_user(joydev->nkey, (__u8 __user *) argp);
+
+	case JSIOCSCORR:
+		if (copy_from_user(joydev->corr, argp,
+			      sizeof(joydev->corr[0]) * joydev->nabs))
+		    return -EFAULT;
+
+		for (i = 0; i < joydev->nabs; i++) {
+			j = joydev->abspam[i];
+			joydev->abs[i] = joydev_correct(dev->abs[j],
+							&joydev->corr[i]);
+		}
+		return 0;
 
-		case JSIOCSAXMAP:
-			if (copy_from_user(joydev->abspam, argp, sizeof(__u8) * (ABS_MAX + 1)))
-				return -EFAULT;
-			for (i = 0; i < joydev->nabs; i++) {
-				if (joydev->abspam[i] > ABS_MAX)
-					return -EINVAL;
-				joydev->absmap[joydev->abspam[i]] = i;
-			}
-			return 0;
-
-		case JSIOCGAXMAP:
-			return copy_to_user(argp, joydev->abspam,
-						sizeof(__u8) * (ABS_MAX + 1)) ? -EFAULT : 0;
+	case JSIOCGCORR:
+		return copy_to_user(argp, joydev->corr,
+			sizeof(joydev->corr[0]) * joydev->nabs) ? -EFAULT : 0;
+
+	case JSIOCSAXMAP:
+		if (copy_from_user(joydev->abspam, argp,
+				   sizeof(__u8) * (ABS_MAX + 1)))
+			return -EFAULT;
+
+		for (i = 0; i < joydev->nabs; i++) {
+			if (joydev->abspam[i] > ABS_MAX)
+				return -EINVAL;
+			joydev->absmap[joydev->abspam[i]] = i;
+		}
+		return 0;
+
+	case JSIOCGAXMAP:
+		return copy_to_user(argp, joydev->abspam,
+			sizeof(__u8) * (ABS_MAX + 1)) ? -EFAULT : 0;
+
+	case JSIOCSBTNMAP:
+		if (copy_from_user(joydev->keypam, argp,
+				   sizeof(__u16) * (KEY_MAX - BTN_MISC + 1)))
+			return -EFAULT;
+
+		for (i = 0; i < joydev->nkey; i++) {
+			if (joydev->keypam[i] > KEY_MAX ||
+			    joydev->keypam[i] < BTN_MISC)
+				return -EINVAL;
+			joydev->keymap[joydev->keypam[i] - BTN_MISC] = i;
+		}
 
-		case JSIOCSBTNMAP:
-			if (copy_from_user(joydev->keypam, argp, sizeof(__u16) * (KEY_MAX - BTN_MISC + 1)))
+		return 0;
+
+	case JSIOCGBTNMAP:
+		return copy_to_user(argp, joydev->keypam,
+			sizeof(__u16) * (KEY_MAX - BTN_MISC + 1)) ? -EFAULT : 0;
+
+	default:
+		if ((cmd & ~IOCSIZE_MASK) == JSIOCGNAME(0)) {
+			int len;
+			if (!dev->name)
+				return 0;
+			len = strlen(dev->name) + 1;
+			if (len > _IOC_SIZE(cmd))
+				len = _IOC_SIZE(cmd);
+			if (copy_to_user(argp, dev->name, len))
 				return -EFAULT;
-			for (i = 0; i < joydev->nkey; i++) {
-				if (joydev->keypam[i] > KEY_MAX || joydev->keypam[i] < BTN_MISC)
-					return -EINVAL;
-				joydev->keymap[joydev->keypam[i] - BTN_MISC] = i;
-			}
-			return 0;
-
-		case JSIOCGBTNMAP:
-			return copy_to_user(argp, joydev->keypam,
-						sizeof(__u16) * (KEY_MAX - BTN_MISC + 1)) ? -EFAULT : 0;
-
-		default:
-			if ((cmd & ~(_IOC_SIZEMASK << _IOC_SIZESHIFT)) == JSIOCGNAME(0)) {
-				int len;
-				if (!dev->name)
-					return 0;
-				len = strlen(dev->name) + 1;
-				if (len > _IOC_SIZE(cmd))
-					len = _IOC_SIZE(cmd);
-				if (copy_to_user(argp, dev->name, len))
-					return -EFAULT;
-				return len;
-			}
+			return len;
+		}
 	}
 	return -EINVAL;
 }
 
 #ifdef CONFIG_COMPAT
-static long joydev_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+static long joydev_compat_ioctl(struct file *file,
+				unsigned int cmd, unsigned long arg)
 {
 	struct joydev_client *client = file->private_data;
 	struct joydev *joydev = client->joydev;
 	void __user *argp = (void __user *)arg;
 	s32 tmp32;
 	struct JS_DATA_SAVE_TYPE_32 ds32;
-	int err;
+	int retval;
 
-	if (!joydev->exist)
-		return -ENODEV;
+	retval = mutex_lock_interruptible(&joydev->mutex);
+	if (retval)
+		return retval;
+
+	if (!joydev->exist) {
+		retval = -ENODEV;
+		goto out;
+	}
+
+	switch (cmd) {
 
-	switch(cmd) {
 	case JS_SET_TIMELIMIT:
-		err = get_user(tmp32, (s32 __user *) arg);
-		if (err == 0)
+		retval = get_user(tmp32, (s32 __user *) arg);
+		if (retval == 0)
 			joydev->glue.JS_TIMELIMIT = tmp32;
 		break;
+
 	case JS_GET_TIMELIMIT:
 		tmp32 = joydev->glue.JS_TIMELIMIT;
-		err = put_user(tmp32, (s32 __user *) arg);
+		retval = put_user(tmp32, (s32 __user *) arg);
 		break;
 
 	case JS_SET_ALL:
-		err = copy_from_user(&ds32, argp,
-				     sizeof(ds32)) ? -EFAULT : 0;
-		if (err == 0) {
+		retval = copy_from_user(&ds32, argp,
+					sizeof(ds32)) ? -EFAULT : 0;
+		if (retval == 0) {
 			joydev->glue.JS_TIMEOUT    = ds32.JS_TIMEOUT;
 			joydev->glue.BUSY          = ds32.BUSY;
 			joydev->glue.JS_EXPIRETIME = ds32.JS_EXPIRETIME;
@@ -438,55 +607,119 @@ static long joydev_compat_ioctl(struct f
 		ds32.JS_SAVE       = joydev->glue.JS_SAVE;
 		ds32.JS_CORR       = joydev->glue.JS_CORR;
 
-		err = copy_to_user(argp, &ds32, sizeof(ds32)) ? -EFAULT : 0;
+		retval = copy_to_user(argp, &ds32, sizeof(ds32)) ? -EFAULT : 0;
 		break;
 
 	default:
-		err = joydev_ioctl_common(joydev, cmd, argp);
+		retval = joydev_ioctl_common(joydev, cmd, argp);
+		break;
 	}
-	return err;
+
+ out:
+	mutex_unlock(&joydev->mutex);
+	return retval;
 }
 #endif /* CONFIG_COMPAT */
 
-static int joydev_ioctl(struct inode *inode, struct file *file, unsigned int cmd, unsigned long arg)
+static long joydev_ioctl(struct file *file,
+			 unsigned int cmd, unsigned long arg)
 {
 	struct joydev_client *client = file->private_data;
 	struct joydev *joydev = client->joydev;
 	void __user *argp = (void __user *)arg;
+	int retval;
 
-	if (!joydev->exist)
-		return -ENODEV;
+	retval = mutex_lock_interruptible(&joydev->mutex);
+	if (retval)
+		return retval;
+
+	if (!joydev->exist) {
+		retval = -ENODEV;
+		goto out;
+	}
+
+	switch (cmd) {
+
+	case JS_SET_TIMELIMIT:
+		retval = get_user(joydev->glue.JS_TIMELIMIT,
+				  (long __user *) arg);
+		break;
+
+	case JS_GET_TIMELIMIT:
+		retval = put_user(joydev->glue.JS_TIMELIMIT,
+				  (long __user *) arg);
+		break;
+
+	case JS_SET_ALL:
+		retval = copy_from_user(&joydev->glue, argp,
+					sizeof(joydev->glue)) ? -EFAULT: 0;
+		break;
 
-	switch(cmd) {
-		case JS_SET_TIMELIMIT:
-			return get_user(joydev->glue.JS_TIMELIMIT, (long __user *) arg);
-		case JS_GET_TIMELIMIT:
-			return put_user(joydev->glue.JS_TIMELIMIT, (long __user *) arg);
-		case JS_SET_ALL:
-			return copy_from_user(&joydev->glue, argp,
-						sizeof(joydev->glue)) ? -EFAULT : 0;
-		case JS_GET_ALL:
-			return copy_to_user(argp, &joydev->glue,
-						sizeof(joydev->glue)) ? -EFAULT : 0;
-		default:
-			return joydev_ioctl_common(joydev, cmd, argp);
+	case JS_GET_ALL:
+		retval = copy_to_user(argp, &joydev->glue,
+				      sizeof(joydev->glue)) ? -EFAULT : 0;
+		break;
+
+	default:
+		retval = joydev_ioctl_common(joydev, cmd, argp);
+		break;
 	}
+ out:
+	mutex_unlock(&joydev->mutex);
+	return retval;
 }
 
 static const struct file_operations joydev_fops = {
-	.owner =	THIS_MODULE,
-	.read =		joydev_read,
-	.write =	joydev_write,
-	.poll =		joydev_poll,
-	.open =		joydev_open,
-	.release =	joydev_release,
-	.ioctl =	joydev_ioctl,
+	.owner		= THIS_MODULE,
+	.read		= joydev_read,
+	.poll		= joydev_poll,
+	.open		= joydev_open,
+	.release	= joydev_release,
+	.unlocked_ioctl	= joydev_ioctl,
 #ifdef CONFIG_COMPAT
-	.compat_ioctl =	joydev_compat_ioctl,
+	.compat_ioctl	= joydev_compat_ioctl,
 #endif
-	.fasync =	joydev_fasync,
+	.fasync		= joydev_fasync,
 };
 
+static int joydev_install_chrdev(struct joydev *joydev)
+{
+	joydev_table[joydev->minor] = joydev;
+	return 0;
+}
+
+static void joydev_remove_chrdev(struct joydev *joydev)
+{
+	mutex_lock(&joydev_table_mutex);
+	joydev_table[joydev->minor] = NULL;
+	mutex_unlock(&joydev_table_mutex);
+}
+
+/*
+ * Mark device non-existant. 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 joydev_mark_dead(struct joydev *joydev)
+{
+	mutex_lock(&joydev->mutex);
+	joydev->exist = 0;
+	mutex_unlock(&joydev->mutex);
+}
+
+static void joydev_cleanup(struct joydev *joydev)
+{
+	struct input_handle *handle = &joydev->handle;
+
+	joydev_mark_dead(joydev);
+	joydev_hangup(joydev);
+	joydev_remove_chrdev(joydev);
+
+	/* joydev is marked dead so noone else accesses joydev->open */
+	if (joydev->open)
+		input_close_device(handle);
+}
+
 static int joydev_connect(struct input_handler *handler, struct input_dev *dev,
 			  const struct input_device_id *id)
 {
@@ -494,7 +727,10 @@ static int joydev_connect(struct input_h
 	int i, j, t, minor;
 	int error;
 
-	for (minor = 0; minor < JOYDEV_MINORS && joydev_table[minor]; minor++);
+	for (minor = 0; minor < JOYDEV_MINORS; minor++)
+		if (!joydev_table[minor])
+			break;
+
 	if (minor == JOYDEV_MINORS) {
 		printk(KERN_ERR "joydev: no more free joydev devices\n");
 		return -ENFILE;
@@ -505,15 +741,19 @@ static int joydev_connect(struct input_h
 		return -ENOMEM;
 
 	INIT_LIST_HEAD(&joydev->client_list);
+	spin_lock_init(&joydev->client_lock);
+	mutex_init(&joydev->mutex);
 	init_waitqueue_head(&joydev->wait);
 
+	snprintf(joydev->name, sizeof(joydev->name), "js%d", minor);
+	joydev->exist = 1;
 	joydev->minor = minor;
+
 	joydev->exist = 1;
 	joydev->handle.dev = dev;
 	joydev->handle.name = joydev->name;
 	joydev->handle.handler = handler;
 	joydev->handle.private = joydev;
-	snprintf(joydev->name, sizeof(joydev->name), "js%d", minor);
 
 	for (i = 0; i < ABS_MAX + 1; i++)
 		if (test_bit(i, dev->absbit)) {
@@ -545,67 +785,65 @@ static int joydev_connect(struct input_h
 		}
 		joydev->corr[i].type = JS_CORR_BROKEN;
 		joydev->corr[i].prec = dev->absfuzz[j];
-		joydev->corr[i].coef[0] = (dev->absmax[j] + dev->absmin[j]) / 2 - dev->absflat[j];
-		joydev->corr[i].coef[1] = (dev->absmax[j] + dev->absmin[j]) / 2 + dev->absflat[j];
-		if (!(t = ((dev->absmax[j] - dev->absmin[j]) / 2 - 2 * dev->absflat[j])))
-			continue;
-		joydev->corr[i].coef[2] = (1 << 29) / t;
-		joydev->corr[i].coef[3] = (1 << 29) / t;
+		joydev->corr[i].coef[0] =
+			(dev->absmax[j] + dev->absmin[j]) / 2 - dev->absflat[j];
+		joydev->corr[i].coef[1] =
+			(dev->absmax[j] + dev->absmin[j]) / 2 + dev->absflat[j];
+
+		t = (dev->absmax[j] - dev->absmin[j]) / 2 - 2 * dev->absflat[j];
+		if (t) {
+			joydev->corr[i].coef[2] = (1 << 29) / t;
+			joydev->corr[i].coef[3] = (1 << 29) / t;
 
-		joydev->abs[i] = joydev_correct(dev->abs[j], joydev->corr + i);
+			joydev->abs[i] = joydev_correct(dev->abs[j],
+							joydev->corr + i);
+		}
 	}
 
-	snprintf(joydev->dev.bus_id, sizeof(joydev->dev.bus_id),
-		 "js%d", minor);
+	strlcpy(joydev->dev.bus_id, joydev->name, sizeof(joydev->dev.bus_id));
+	joydev->dev.devt = MKDEV(INPUT_MAJOR, JOYDEV_MINOR_BASE + minor);
 	joydev->dev.class = &input_class;
 	joydev->dev.parent = &dev->dev;
-	joydev->dev.devt = MKDEV(INPUT_MAJOR, JOYDEV_MINOR_BASE + minor);
 	joydev->dev.release = joydev_free;
 	device_initialize(&joydev->dev);
 
-	joydev_table[minor] = joydev;
-
-	error = device_add(&joydev->dev);
+	error = input_register_handle(&joydev->handle);
 	if (error)
 		goto err_free_joydev;
 
-	error = input_register_handle(&joydev->handle);
+	error = joydev_install_chrdev(joydev);
 	if (error)
-		goto err_delete_joydev;
+		goto err_unregister_handle;
+
+	error = device_add(&joydev->dev);
+	if (error)
+		goto err_cleanup_joydev;
 
 	return 0;
 
- err_delete_joydev:
-	device_del(&joydev->dev);
+ err_cleanup_joydev:
+	joydev_cleanup(joydev);
+ err_unregister_handle:
+	input_unregister_handle(&joydev->handle);
  err_free_joydev:
 	put_device(&joydev->dev);
 	return error;
 }
 
-
 static void joydev_disconnect(struct input_handle *handle)
 {
 	struct joydev *joydev = handle->private;
-	struct joydev_client *client;
 
-	input_unregister_handle(handle);
 	device_del(&joydev->dev);
-
-	joydev->exist = 0;
-
-	if (joydev->open) {
-		input_close_device(handle);
-		list_for_each_entry(client, &joydev->client_list, node)
-			kill_fasync(&client->fasync, SIGIO, POLL_HUP);
-		wake_up_interruptible(&joydev->wait);
-	}
-
+	joydev_cleanup(joydev);
+	input_unregister_handle(handle);
 	put_device(&joydev->dev);
 }
 
 static const struct input_device_id joydev_blacklist[] = {
 	{
-		.flags = INPUT_DEVICE_ID_MATCH_EVBIT | INPUT_DEVICE_ID_MATCH_KEYBIT,
+		.flags = INPUT_DEVICE_ID_MATCH_EVBIT |
+				INPUT_DEVICE_ID_MATCH_KEYBIT,
 		.evbit = { BIT(EV_KEY) },
 		.keybit = { [LONG(BTN_TOUCH)] = BIT(BTN_TOUCH) },
 	},	/* Avoid itouchpads, touchscreens and tablets */
@@ -614,17 +852,20 @@ static const struct input_device_id joyd
 
 static const struct input_device_id joydev_ids[] = {
 	{
-		.flags = INPUT_DEVICE_ID_MATCH_EVBIT | INPUT_DEVICE_ID_MATCH_ABSBIT,
+		.flags = INPUT_DEVICE_ID_MATCH_EVBIT |
+				INPUT_DEVICE_ID_MATCH_ABSBIT,
 		.evbit = { BIT(EV_ABS) },
 		.absbit = { BIT(ABS_X) },
 	},
 	{
-		.flags = INPUT_DEVICE_ID_MATCH_EVBIT | INPUT_DEVICE_ID_MATCH_ABSBIT,
+		.flags = INPUT_DEVICE_ID_MATCH_EVBIT |
+				INPUT_DEVICE_ID_MATCH_ABSBIT,
 		.evbit = { BIT(EV_ABS) },
 		.absbit = { BIT(ABS_WHEEL) },
 	},
 	{
-		.flags = INPUT_DEVICE_ID_MATCH_EVBIT | INPUT_DEVICE_ID_MATCH_ABSBIT,
+		.flags = INPUT_DEVICE_ID_MATCH_EVBIT |
+				INPUT_DEVICE_ID_MATCH_ABSBIT,
 		.evbit = { BIT(EV_ABS) },
 		.absbit = { BIT(ABS_THROTTLE) },
 	},
@@ -634,14 +875,14 @@ static const struct input_device_id joyd
 MODULE_DEVICE_TABLE(input, joydev_ids);
 
 static struct input_handler joydev_handler = {
-	.event =	joydev_event,
-	.connect =	joydev_connect,
-	.disconnect =	joydev_disconnect,
-	.fops =		&joydev_fops,
-	.minor =	JOYDEV_MINOR_BASE,
-	.name =		"joydev",
-	.id_table =	joydev_ids,
-	.blacklist =	joydev_blacklist,
+	.event		= joydev_event,
+	.connect	= joydev_connect,
+	.disconnect	= joydev_disconnect,
+	.fops		= &joydev_fops,
+	.minor		= JOYDEV_MINOR_BASE,
+	.name		= "joydev",
+	.id_table	= joydev_ids,
+	.blacklist	= joydev_blacklist,
 };
 
 static int __init joydev_init(void)