Merge commit 'v2.6.37-rc7' into devicetree/next

[cascardo/linux.git] / drivers / media / video / v4l2-dev.c

diff --git a/drivers/media/video/v4l2-dev.c b/drivers/media/video/v4l2-dev.c
index 03f7f46..359e232 100644 (file)
--- 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);