diff options
Diffstat (limited to 'drivers/media/video/v4l2-dev.c')
| -rw-r--r-- | drivers/media/video/v4l2-dev.c | 69 |
1 files changed, 51 insertions, 18 deletions
diff --git a/drivers/media/video/v4l2-dev.c b/drivers/media/video/v4l2-dev.c index 03f7f4670e9..359e23290a7 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); |