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Subject[patch 52/73] Input: tsdev - implement proper locking
2.6.23-stable review patch.  If anyone has any objections, please let us know.
------------------
From: Dmitry Torokhov <dmitry.torokhov@gmail.com>
patch b9d2d110b10f7b4788d0fdd328cf57e34b767817 in mainline.

Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
drivers/input/tsdev.c | 392 +++++++++++++++++++++++++++++++++++---------------
1 file changed, 278 insertions(+), 114 deletions(-)
--- a/drivers/input/tsdev.c
+++ b/drivers/input/tsdev.c
@@ -112,6 +112,8 @@ struct tsdev {
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;

int x, y, pressure;
@@ -122,8 +124,9 @@ struct tsdev_client {
struct fasync_struct *fasync;
struct list_head node;
struct tsdev *tsdev;
+ struct ts_event buffer[TSDEV_BUFFER_SIZE];
int head, tail;
- struct ts_event event[TSDEV_BUFFER_SIZE];
+ spinlock_t buffer_lock; /* protects access to buffer, head and tail */
int raw;
};

@@ -137,6 +140,7 @@ struct tsdev_client {
#define TS_SET_CAL _IOW(IOC_H3600_TS_MAGIC, 11, struct ts_calibration)

static struct tsdev *tsdev_table[TSDEV_MINORS/2];
+static DEFINE_MUTEX(tsdev_table_mutex);

static int tsdev_fasync(int fd, struct file *file, int on)
{
@@ -144,9 +148,91 @@ static int tsdev_fasync(int fd, struct f
int retval;

retval = fasync_helper(fd, file, on, &client->fasync);
+
return retval < 0 ? retval : 0;
}

+static void tsdev_free(struct device *dev)
+{
+ struct tsdev *tsdev = container_of(dev, struct tsdev, dev);
+
+ kfree(tsdev);
+}
+
+static void tsdev_attach_client(struct tsdev *tsdev, struct tsdev_client *client)
+{
+ spin_lock(&tsdev->client_lock);
+ list_add_tail_rcu(&client->node, &tsdev->client_list);
+ spin_unlock(&tsdev->client_lock);
+ synchronize_sched();
+}
+
+static void tsdev_detach_client(struct tsdev *tsdev, struct tsdev_client *client)
+{
+ spin_lock(&tsdev->client_lock);
+ list_del_rcu(&client->node);
+ spin_unlock(&tsdev->client_lock);
+ synchronize_sched();
+}
+
+static int tsdev_open_device(struct tsdev *tsdev)
+{
+ int retval;
+
+ retval = mutex_lock_interruptible(&tsdev->mutex);
+ if (retval)
+ return retval;
+
+ if (!tsdev->exist)
+ retval = -ENODEV;
+ else if (!tsdev->open++)
+ retval = input_open_device(&tsdev->handle);
+
+ mutex_unlock(&tsdev->mutex);
+ return retval;
+}
+
+static void tsdev_close_device(struct tsdev *tsdev)
+{
+ mutex_lock(&tsdev->mutex);
+
+ if (tsdev->exist && !--tsdev->open)
+ input_close_device(&tsdev->handle);
+
+ mutex_unlock(&tsdev->mutex);
+}
+
+/*
+ * Wake up users waiting for IO so they can disconnect from
+ * dead device.
+ */
+static void tsdev_hangup(struct tsdev *tsdev)
+{
+ struct tsdev_client *client;
+
+ spin_lock(&tsdev->client_lock);
+ list_for_each_entry(client, &tsdev->client_list, node)
+ kill_fasync(&client->fasync, SIGIO, POLL_HUP);
+ spin_unlock(&tsdev->client_lock);
+
+ wake_up_interruptible(&tsdev->wait);
+}
+
+static int tsdev_release(struct inode *inode, struct file *file)
+{
+ struct tsdev_client *client = file->private_data;
+ struct tsdev *tsdev = client->tsdev;
+
+ tsdev_fasync(-1, file, 0);
+ tsdev_detach_client(tsdev, client);
+ kfree(client);
+
+ tsdev_close_device(tsdev);
+ put_device(&tsdev->dev);
+
+ return 0;
+}
+
static int tsdev_open(struct inode *inode, struct file *file)
{
int i = iminor(inode) - TSDEV_MINOR_BASE;
@@ -161,11 +247,16 @@ static int tsdev_open(struct inode *inod
if (i >= TSDEV_MINORS)
return -ENODEV;

+ error = mutex_lock_interruptible(&tsdev_table_mutex);
+ if (error)
+ return error;
tsdev = tsdev_table[i & TSDEV_MINOR_MASK];
- if (!tsdev || !tsdev->exist)
- return -ENODEV;
+ if (tsdev)
+ get_device(&tsdev->dev);
+ mutex_unlock(&tsdev_table_mutex);

- get_device(&tsdev->dev);
+ if (!tsdev)
+ return -ENODEV;

client = kzalloc(sizeof(struct tsdev_client), GFP_KERNEL);
if (!client) {
@@ -173,51 +264,42 @@ static int tsdev_open(struct inode *inod
goto err_put_tsdev;
}

+ spin_lock_init(&client->buffer_lock);
client->tsdev = tsdev;
- client->raw = (i >= TSDEV_MINORS / 2) ? 1 : 0;
- list_add_tail(&client->node, &tsdev->client_list);
+ client->raw = i >= TSDEV_MINORS / 2;
+ tsdev_attach_client(tsdev, client);

- if (!tsdev->open++ && tsdev->exist) {
- error = input_open_device(&tsdev->handle);
- if (error)
- goto err_free_client;
- }
+ error = tsdev_open_device(tsdev);
+ if (error)
+ goto err_free_client;

file->private_data = client;
return 0;

err_free_client:
- list_del(&client->node);
+ tsdev_detach_client(tsdev, client);
kfree(client);
err_put_tsdev:
put_device(&tsdev->dev);
return error;
}

-static void tsdev_free(struct device *dev)
+static int tsdev_fetch_next_event(struct tsdev_client *client,
+ struct ts_event *event)
{
- struct tsdev *tsdev = container_of(dev, struct tsdev, dev);
+ int have_event;

- tsdev_table[tsdev->minor] = NULL;
- kfree(tsdev);
-}
-
-static int tsdev_release(struct inode *inode, struct file *file)
-{
- struct tsdev_client *client = file->private_data;
- struct tsdev *tsdev = client->tsdev;
-
- tsdev_fasync(-1, file, 0);
+ spin_lock_irq(&client->buffer_lock);

- list_del(&client->node);
- kfree(client);
-
- if (!--tsdev->open && tsdev->exist)
- input_close_device(&tsdev->handle);
+ have_event = client->head != client->tail;
+ if (have_event) {
+ *event = client->buffer[client->tail++];
+ client->tail &= TSDEV_BUFFER_SIZE - 1;
+ }

- put_device(&tsdev->dev);
+ spin_unlock_irq(&client->buffer_lock);

- return 0;
+ return have_event;
}

static ssize_t tsdev_read(struct file *file, char __user *buffer, size_t count,
@@ -225,9 +307,11 @@ static ssize_t tsdev_read(struct file *f
{
struct tsdev_client *client = file->private_data;
struct tsdev *tsdev = client->tsdev;
- int retval = 0;
+ struct ts_event event;
+ int retval;

- if (client->head == client->tail && tsdev->exist && (file->f_flags & O_NONBLOCK))
+ if (client->head == client->tail && tsdev->exist &&
+ (file->f_flags & O_NONBLOCK))
return -EAGAIN;

retval = wait_event_interruptible(tsdev->wait,
@@ -238,13 +322,14 @@ static ssize_t tsdev_read(struct file *f
if (!tsdev->exist)
return -ENODEV;

- while (client->head != client->tail &&
- retval + sizeof (struct ts_event) <= count) {
- if (copy_to_user (buffer + retval, client->event + client->tail,
- sizeof (struct ts_event)))
+ while (retval + sizeof(struct ts_event) <= count &&
+ tsdev_fetch_next_event(client, &event)) {
+
+ if (copy_to_user(buffer + retval, &event,
+ sizeof(struct ts_event)))
return -EFAULT;
- client->tail = (client->tail + 1) & (TSDEV_BUFFER_SIZE - 1);
- retval += sizeof (struct ts_event);
+
+ retval += sizeof(struct ts_event);
}

return retval;
@@ -261,14 +346,23 @@ static unsigned int tsdev_poll(struct fi
(tsdev->exist ? 0 : (POLLHUP | POLLERR));
}

-static int tsdev_ioctl(struct inode *inode, struct file *file,
- unsigned int cmd, unsigned long arg)
+static long tsdev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
struct tsdev_client *client = file->private_data;
struct tsdev *tsdev = client->tsdev;
int retval = 0;

+ retval = mutex_lock_interruptible(&tsdev->mutex);
+ if (retval)
+ return retval;
+
+ if (!tsdev->exist) {
+ retval = -ENODEV;
+ goto out;
+ }
+
switch (cmd) {
+
case TS_GET_CAL:
if (copy_to_user((void __user *)arg, &tsdev->cal,
sizeof (struct ts_calibration)))
@@ -277,7 +371,7 @@ static int tsdev_ioctl(struct inode *ino

case TS_SET_CAL:
if (copy_from_user(&tsdev->cal, (void __user *)arg,
- sizeof (struct ts_calibration)))
+ sizeof(struct ts_calibration)))
retval = -EFAULT;
break;

@@ -286,29 +380,79 @@ static int tsdev_ioctl(struct inode *ino
break;
}

+ out:
+ mutex_unlock(&tsdev->mutex);
return retval;
}

static const struct file_operations tsdev_fops = {
- .owner = THIS_MODULE,
- .open = tsdev_open,
- .release = tsdev_release,
- .read = tsdev_read,
- .poll = tsdev_poll,
- .fasync = tsdev_fasync,
- .ioctl = tsdev_ioctl,
+ .owner = THIS_MODULE,
+ .open = tsdev_open,
+ .release = tsdev_release,
+ .read = tsdev_read,
+ .poll = tsdev_poll,
+ .fasync = tsdev_fasync,
+ .unlocked_ioctl = tsdev_ioctl,
};

+static void tsdev_pass_event(struct tsdev *tsdev, struct tsdev_client *client,
+ int x, int y, int pressure, int millisecs)
+{
+ struct ts_event *event;
+ int tmp;
+
+ /* Interrupts are already disabled, just acquire the lock */
+ spin_lock(&client->buffer_lock);
+
+ event = &client->buffer[client->head++];
+ client->head &= TSDEV_BUFFER_SIZE - 1;
+
+ /* Calibration */
+ if (!client->raw) {
+ x = ((x * tsdev->cal.xscale) >> 8) + tsdev->cal.xtrans;
+ y = ((y * tsdev->cal.yscale) >> 8) + tsdev->cal.ytrans;
+ if (tsdev->cal.xyswap) {
+ tmp = x; x = y; y = tmp;
+ }
+ }
+
+ event->millisecs = millisecs;
+ event->x = x;
+ event->y = y;
+ event->pressure = pressure;
+
+ spin_unlock(&client->buffer_lock);
+
+ kill_fasync(&client->fasync, SIGIO, POLL_IN);
+}
+
+static void tsdev_distribute_event(struct tsdev *tsdev)
+{
+ struct tsdev_client *client;
+ struct timeval time;
+ int millisecs;
+
+ do_gettimeofday(&time);
+ millisecs = time.tv_usec / 1000;
+
+ list_for_each_entry_rcu(client, &tsdev->client_list, node)
+ tsdev_pass_event(tsdev, client,
+ tsdev->x, tsdev->y,
+ tsdev->pressure, millisecs);
+}
+
static void tsdev_event(struct input_handle *handle, unsigned int type,
unsigned int code, int value)
{
struct tsdev *tsdev = handle->private;
- struct tsdev_client *client;
- struct timeval time;
+ struct input_dev *dev = handle->dev;
+ int wake_up_readers = 0;

switch (type) {
+
case EV_ABS:
switch (code) {
+
case ABS_X:
tsdev->x = value;
break;
@@ -318,9 +462,9 @@ static void tsdev_event(struct input_han
break;

case ABS_PRESSURE:
- if (value > handle->dev->absmax[ABS_PRESSURE])
- value = handle->dev->absmax[ABS_PRESSURE];
- value -= handle->dev->absmin[ABS_PRESSURE];
+ if (value > dev->absmax[ABS_PRESSURE])
+ value = dev->absmax[ABS_PRESSURE];
+ value -= dev->absmin[ABS_PRESSURE];
if (value < 0)
value = 0;
tsdev->pressure = value;
@@ -330,6 +474,7 @@ static void tsdev_event(struct input_han

case EV_REL:
switch (code) {
+
case REL_X:
tsdev->x += value;
if (tsdev->x < 0)
@@ -351,6 +496,7 @@ static void tsdev_event(struct input_han
case EV_KEY:
if (code == BTN_TOUCH || code == BTN_MOUSE) {
switch (value) {
+
case 0:
tsdev->pressure = 0;
break;
@@ -362,49 +508,71 @@ static void tsdev_event(struct input_han
}
}
break;
+
+ case EV_SYN:
+ if (code == SYN_REPORT) {
+ tsdev_distribute_event(tsdev);
+ wake_up_readers = 1;
+ }
+ break;
}

- if (type != EV_SYN || code != SYN_REPORT)
- return;
+ if (wake_up_readers)
+ wake_up_interruptible(&tsdev->wait);
+}

- list_for_each_entry(client, &tsdev->client_list, node) {
- int x, y, tmp;
+static int tsdev_install_chrdev(struct tsdev *tsdev)
+{
+ tsdev_table[tsdev->minor] = tsdev;
+ return 0;
+}

- do_gettimeofday(&time);
- client->event[client->head].millisecs = time.tv_usec / 1000;
- client->event[client->head].pressure = tsdev->pressure;
-
- x = tsdev->x;
- y = tsdev->y;
-
- /* Calibration */
- if (!client->raw) {
- x = ((x * tsdev->cal.xscale) >> 8) + tsdev->cal.xtrans;
- y = ((y * tsdev->cal.yscale) >> 8) + tsdev->cal.ytrans;
- if (tsdev->cal.xyswap) {
- tmp = x; x = y; y = tmp;
- }
- }
+static void tsdev_remove_chrdev(struct tsdev *tsdev)
+{
+ mutex_lock(&tsdev_table_mutex);
+ tsdev_table[tsdev->minor] = NULL;
+ mutex_unlock(&tsdev_table_mutex);
+}

- client->event[client->head].x = x;
- client->event[client->head].y = y;
- client->head = (client->head + 1) & (TSDEV_BUFFER_SIZE - 1);
- kill_fasync(&client->fasync, SIGIO, POLL_IN);
- }
- wake_up_interruptible(&tsdev->wait);
+/*
+ * 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 tsdev_mark_dead(struct tsdev *tsdev)
+{
+ mutex_lock(&tsdev->mutex);
+ tsdev->exist = 0;
+ mutex_unlock(&tsdev->mutex);
+}
+
+static void tsdev_cleanup(struct tsdev *tsdev)
+{
+ struct input_handle *handle = &tsdev->handle;
+
+ tsdev_mark_dead(tsdev);
+ tsdev_hangup(tsdev);
+ tsdev_remove_chrdev(tsdev);
+
+ /* tsdev is marked dead so noone else accesses tsdev->open */
+ if (tsdev->open)
+ input_close_device(handle);
}

static int tsdev_connect(struct input_handler *handler, struct input_dev *dev,
const struct input_device_id *id)
{
struct tsdev *tsdev;
- int minor, delta;
+ int delta;
+ int minor;
int error;

- for (minor = 0; minor < TSDEV_MINORS / 2 && tsdev_table[minor]; minor++);
- if (minor >= TSDEV_MINORS / 2) {
- printk(KERN_ERR
- "tsdev: You have way too many touchscreens\n");
+ for (minor = 0; minor < TSDEV_MINORS / 2; minor++)
+ if (!tsdev_table[minor])
+ break;
+
+ if (minor == TSDEV_MINORS) {
+ printk(KERN_ERR "tsdev: no more free tsdev devices\n");
return -ENFILE;
}

@@ -413,15 +581,18 @@ static int tsdev_connect(struct input_ha
return -ENOMEM;

INIT_LIST_HEAD(&tsdev->client_list);
+ spin_lock_init(&tsdev->client_lock);
+ mutex_init(&tsdev->mutex);
init_waitqueue_head(&tsdev->wait);

+ snprintf(tsdev->name, sizeof(tsdev->name), "ts%d", minor);
tsdev->exist = 1;
tsdev->minor = minor;
+
tsdev->handle.dev = dev;
tsdev->handle.name = tsdev->name;
tsdev->handle.handler = handler;
tsdev->handle.private = tsdev;
- snprintf(tsdev->name, sizeof(tsdev->name), "ts%d", minor);

/* Precompute the rough calibration matrix */
delta = dev->absmax [ABS_X] - dev->absmin [ABS_X] + 1;
@@ -436,28 +607,31 @@ static int tsdev_connect(struct input_ha
tsdev->cal.yscale = (yres << 8) / delta;
tsdev->cal.ytrans = - ((dev->absmin [ABS_Y] * tsdev->cal.yscale) >> 8);

- snprintf(tsdev->dev.bus_id, sizeof(tsdev->dev.bus_id),
- "ts%d", minor);
+ strlcpy(tsdev->dev.bus_id, tsdev->name, sizeof(tsdev->dev.bus_id));
+ tsdev->dev.devt = MKDEV(INPUT_MAJOR, TSDEV_MINOR_BASE + minor);
tsdev->dev.class = &input_class;
tsdev->dev.parent = &dev->dev;
- tsdev->dev.devt = MKDEV(INPUT_MAJOR, TSDEV_MINOR_BASE + minor);
tsdev->dev.release = tsdev_free;
device_initialize(&tsdev->dev);

- tsdev_table[minor] = tsdev;
-
- error = device_add(&tsdev->dev);
+ error = input_register_handle(&tsdev->handle);
if (error)
goto err_free_tsdev;

- error = input_register_handle(&tsdev->handle);
+ error = tsdev_install_chrdev(tsdev);
if (error)
- goto err_delete_tsdev;
+ goto err_unregister_handle;
+
+ error = device_add(&tsdev->dev);
+ if (error)
+ goto err_cleanup_tsdev;

return 0;

- err_delete_tsdev:
- device_del(&tsdev->dev);
+ err_cleanup_tsdev:
+ tsdev_cleanup(tsdev);
+ err_unregister_handle:
+ input_unregister_handle(&tsdev->handle);
err_free_tsdev:
put_device(&tsdev->dev);
return error;
@@ -466,20 +640,10 @@ static int tsdev_connect(struct input_ha
static void tsdev_disconnect(struct input_handle *handle)
{
struct tsdev *tsdev = handle->private;
- struct tsdev_client *client;

- input_unregister_handle(handle);
device_del(&tsdev->dev);
-
- tsdev->exist = 0;
-
- if (tsdev->open) {
- input_close_device(handle);
- list_for_each_entry(client, &tsdev->client_list, node)
- kill_fasync(&client->fasync, SIGIO, POLL_HUP);
- wake_up_interruptible(&tsdev->wait);
- }
-
+ tsdev_cleanup(tsdev);
+ input_unregister_handle(handle);
put_device(&tsdev->dev);
}

@@ -510,13 +674,13 @@ static const struct input_device_id tsde
MODULE_DEVICE_TABLE(input, tsdev_ids);

static struct input_handler tsdev_handler = {
- .event = tsdev_event,
- .connect = tsdev_connect,
- .disconnect = tsdev_disconnect,
- .fops = &tsdev_fops,
- .minor = TSDEV_MINOR_BASE,
- .name = "tsdev",
- .id_table = tsdev_ids,
+ .event = tsdev_event,
+ .connect = tsdev_connect,
+ .disconnect = tsdev_disconnect,
+ .fops = &tsdev_fops,
+ .minor = TSDEV_MINOR_BASE,
+ .name = "tsdev",
+ .id_table = tsdev_ids,
};

static int __init tsdev_init(void)
--


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