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);