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path: root/drivers/media/video/v4l2-dev.c
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Diffstat (limited to 'drivers/media/video/v4l2-dev.c')
-rw-r--r--drivers/media/video/v4l2-dev.c69
1 files changed, 51 insertions, 18 deletions
diff --git a/drivers/media/video/v4l2-dev.c b/drivers/media/video/v4l2-dev.c
index 03f7f4670e9b..359e23290a7e 100644
--- a/drivers/media/video/v4l2-dev.c
+++ b/drivers/media/video/v4l2-dev.c
@@ -186,12 +186,12 @@ static ssize_t v4l2_read(struct file *filp, char __user *buf,
size_t sz, loff_t *off)
{
struct video_device *vdev = video_devdata(filp);
- int ret = -EIO;
+ int ret = -ENODEV;
if (!vdev->fops->read)
return -EINVAL;
- if (vdev->lock)
- mutex_lock(vdev->lock);
+ if (vdev->lock && mutex_lock_interruptible(vdev->lock))
+ return -ERESTARTSYS;
if (video_is_registered(vdev))
ret = vdev->fops->read(filp, buf, sz, off);
if (vdev->lock)
@@ -203,12 +203,12 @@ static ssize_t v4l2_write(struct file *filp, const char __user *buf,
size_t sz, loff_t *off)
{
struct video_device *vdev = video_devdata(filp);
- int ret = -EIO;
+ int ret = -ENODEV;
if (!vdev->fops->write)
return -EINVAL;
- if (vdev->lock)
- mutex_lock(vdev->lock);
+ if (vdev->lock && mutex_lock_interruptible(vdev->lock))
+ return -ERESTARTSYS;
if (video_is_registered(vdev))
ret = vdev->fops->write(filp, buf, sz, off);
if (vdev->lock)
@@ -219,10 +219,10 @@ static ssize_t v4l2_write(struct file *filp, const char __user *buf,
static unsigned int v4l2_poll(struct file *filp, struct poll_table_struct *poll)
{
struct video_device *vdev = video_devdata(filp);
- int ret = DEFAULT_POLLMASK;
+ int ret = POLLERR | POLLHUP;
if (!vdev->fops->poll)
- return ret;
+ return DEFAULT_POLLMASK;
if (vdev->lock)
mutex_lock(vdev->lock);
if (video_is_registered(vdev))
@@ -238,20 +238,45 @@ static long v4l2_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
int ret = -ENODEV;
if (vdev->fops->unlocked_ioctl) {
- if (vdev->lock)
- mutex_lock(vdev->lock);
+ if (vdev->lock && mutex_lock_interruptible(vdev->lock))
+ return -ERESTARTSYS;
if (video_is_registered(vdev))
ret = vdev->fops->unlocked_ioctl(filp, cmd, arg);
if (vdev->lock)
mutex_unlock(vdev->lock);
} else if (vdev->fops->ioctl) {
- /* TODO: convert all drivers to unlocked_ioctl */
+ /* This code path is a replacement for the BKL. It is a major
+ * hack but it will have to do for those drivers that are not
+ * yet converted to use unlocked_ioctl.
+ *
+ * There are two options: if the driver implements struct
+ * v4l2_device, then the lock defined there is used to
+ * serialize the ioctls. Otherwise the v4l2 core lock defined
+ * below is used. This lock is really bad since it serializes
+ * completely independent devices.
+ *
+ * Both variants suffer from the same problem: if the driver
+ * sleeps, then it blocks all ioctls since the lock is still
+ * held. This is very common for VIDIOC_DQBUF since that
+ * normally waits for a frame to arrive. As a result any other
+ * ioctl calls will proceed very, very slowly since each call
+ * will have to wait for the VIDIOC_QBUF to finish. Things that
+ * should take 0.01s may now take 10-20 seconds.
+ *
+ * The workaround is to *not* take the lock for VIDIOC_DQBUF.
+ * This actually works OK for videobuf-based drivers, since
+ * videobuf will take its own internal lock.
+ */
static DEFINE_MUTEX(v4l2_ioctl_mutex);
+ struct mutex *m = vdev->v4l2_dev ?
+ &vdev->v4l2_dev->ioctl_lock : &v4l2_ioctl_mutex;
- mutex_lock(&v4l2_ioctl_mutex);
+ if (cmd != VIDIOC_DQBUF && mutex_lock_interruptible(m))
+ return -ERESTARTSYS;
if (video_is_registered(vdev))
ret = vdev->fops->ioctl(filp, cmd, arg);
- mutex_unlock(&v4l2_ioctl_mutex);
+ if (cmd != VIDIOC_DQBUF)
+ mutex_unlock(m);
} else
ret = -ENOTTY;
@@ -265,8 +290,8 @@ static int v4l2_mmap(struct file *filp, struct vm_area_struct *vm)
if (!vdev->fops->mmap)
return ret;
- if (vdev->lock)
- mutex_lock(vdev->lock);
+ if (vdev->lock && mutex_lock_interruptible(vdev->lock))
+ return -ERESTARTSYS;
if (video_is_registered(vdev))
ret = vdev->fops->mmap(filp, vm);
if (vdev->lock)
@@ -284,7 +309,7 @@ static int v4l2_open(struct inode *inode, struct file *filp)
mutex_lock(&videodev_lock);
vdev = video_devdata(filp);
/* return ENODEV if the video device has already been removed. */
- if (vdev == NULL) {
+ if (vdev == NULL || !video_is_registered(vdev)) {
mutex_unlock(&videodev_lock);
return -ENODEV;
}
@@ -292,8 +317,10 @@ static int v4l2_open(struct inode *inode, struct file *filp)
video_get(vdev);
mutex_unlock(&videodev_lock);
if (vdev->fops->open) {
- if (vdev->lock)
- mutex_lock(vdev->lock);
+ if (vdev->lock && mutex_lock_interruptible(vdev->lock)) {
+ ret = -ERESTARTSYS;
+ goto err;
+ }
if (video_is_registered(vdev))
ret = vdev->fops->open(filp);
else
@@ -302,6 +329,7 @@ static int v4l2_open(struct inode *inode, struct file *filp)
mutex_unlock(vdev->lock);
}
+err:
/* decrease the refcount in case of an error */
if (ret)
video_put(vdev);
@@ -596,7 +624,12 @@ void video_unregister_device(struct video_device *vdev)
if (!vdev || !video_is_registered(vdev))
return;
+ mutex_lock(&videodev_lock);
+ /* This must be in a critical section to prevent a race with v4l2_open.
+ * Once this bit has been cleared video_get may never be called again.
+ */
clear_bit(V4L2_FL_REGISTERED, &vdev->flags);
+ mutex_unlock(&videodev_lock);
device_unregister(&vdev->dev);
}
EXPORT_SYMBOL(video_unregister_device);

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