diff options
| -rw-r--r-- | drivers/media/video/v4l2-dev.c | 31 | ||||
| -rw-r--r-- | drivers/media/video/v4l2-device.c | 1 | ||||
| -rw-r--r-- | include/media/v4l2-device.h | 2 |
3 files changed, 31 insertions, 3 deletions
diff --git a/drivers/media/video/v4l2-dev.c b/drivers/media/video/v4l2-dev.c index bfd392e2436d..6b64fd607b20 100644 --- a/drivers/media/video/v4l2-dev.c +++ b/drivers/media/video/v4l2-dev.c @@ -245,13 +245,38 @@ static long v4l2_ioctl(struct file *filp, unsigned int cmd, unsigned long 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; diff --git a/drivers/media/video/v4l2-device.c b/drivers/media/video/v4l2-device.c index 0b08f96b74a5..7fe6f92af480 100644 --- a/drivers/media/video/v4l2-device.c +++ b/drivers/media/video/v4l2-device.c @@ -35,6 +35,7 @@ int v4l2_device_register(struct device *dev, struct v4l2_device *v4l2_dev) INIT_LIST_HEAD(&v4l2_dev->subdevs); spin_lock_init(&v4l2_dev->lock); + mutex_init(&v4l2_dev->ioctl_lock); v4l2_dev->dev = dev; if (dev == NULL) { /* If dev == NULL, then name must be filled in by the caller */ diff --git a/include/media/v4l2-device.h b/include/media/v4l2-device.h index 6648036b728d..b16f307d471a 100644 --- a/include/media/v4l2-device.h +++ b/include/media/v4l2-device.h @@ -51,6 +51,8 @@ struct v4l2_device { unsigned int notification, void *arg); /* The control handler. May be NULL. */ struct v4l2_ctrl_handler *ctrl_handler; + /* BKL replacement mutex. Temporary solution only. */ + struct mutex ioctl_lock; }; /* Initialize v4l2_dev and make dev->driver_data point to v4l2_dev. |