V4L/DVB: v4l2: add core serialization lock
Drivers can optionally set a pointer to a mutex in struct video_device.
The core will use that to lock before calling open, read, write, unlocked_ioctl,
poll, mmap or release.
Updated the documentation as well and ensure that v4l2-event knows about the
lock: it will unlock it before doing a blocking wait on an event and relock it
afterwards.
Ensure that the 'video_is_registered' check is done when the lock is held:
a typical disconnect will take the lock as well before unregistering the
device nodes, so to prevent race conditions the video_is_registered check
should also be done with the lock held.
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
diff --git a/drivers/media/video/v4l2-dev.c b/drivers/media/video/v4l2-dev.c
index 5a54eab..a7702e3 100644
--- a/drivers/media/video/v4l2-dev.c
+++ b/drivers/media/video/v4l2-dev.c
@@ -187,33 +187,50 @@
size_t sz, loff_t *off)
{
struct video_device *vdev = video_devdata(filp);
+ int ret = -EIO;
if (!vdev->fops->read)
return -EINVAL;
- if (!video_is_registered(vdev))
- return -EIO;
- return vdev->fops->read(filp, buf, sz, off);
+ if (vdev->lock)
+ mutex_lock(vdev->lock);
+ if (video_is_registered(vdev))
+ ret = vdev->fops->read(filp, buf, sz, off);
+ if (vdev->lock)
+ mutex_unlock(vdev->lock);
+ return ret;
}
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;
if (!vdev->fops->write)
return -EINVAL;
- if (!video_is_registered(vdev))
- return -EIO;
- return vdev->fops->write(filp, buf, sz, off);
+ if (vdev->lock)
+ mutex_lock(vdev->lock);
+ if (video_is_registered(vdev))
+ ret = vdev->fops->write(filp, buf, sz, off);
+ if (vdev->lock)
+ mutex_unlock(vdev->lock);
+ return ret;
}
static unsigned int v4l2_poll(struct file *filp, struct poll_table_struct *poll)
{
struct video_device *vdev = video_devdata(filp);
+ int ret = DEFAULT_POLLMASK;
- if (!vdev->fops->poll || !video_is_registered(vdev))
- return DEFAULT_POLLMASK;
- return vdev->fops->poll(filp, poll);
+ if (!vdev->fops->poll)
+ return ret;
+ if (vdev->lock)
+ mutex_lock(vdev->lock);
+ if (video_is_registered(vdev))
+ ret = vdev->fops->poll(filp, poll);
+ if (vdev->lock)
+ mutex_unlock(vdev->lock);
+ return ret;
}
static long v4l2_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
@@ -224,7 +241,11 @@
if (!vdev->fops->ioctl)
return -ENOTTY;
if (vdev->fops->unlocked_ioctl) {
+ if (vdev->lock)
+ mutex_lock(vdev->lock);
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 */
lock_kernel();
@@ -239,10 +260,17 @@
static int v4l2_mmap(struct file *filp, struct vm_area_struct *vm)
{
struct video_device *vdev = video_devdata(filp);
+ int ret = -ENODEV;
- if (!vdev->fops->mmap || !video_is_registered(vdev))
- return -ENODEV;
- return vdev->fops->mmap(filp, vm);
+ if (!vdev->fops->mmap)
+ return ret;
+ if (vdev->lock)
+ mutex_lock(vdev->lock);
+ if (video_is_registered(vdev))
+ ret = vdev->fops->mmap(filp, vm);
+ if (vdev->lock)
+ mutex_unlock(vdev->lock);
+ return ret;
}
/* Override for the open function */
@@ -254,17 +282,24 @@
/* Check if the video device is available */
mutex_lock(&videodev_lock);
vdev = video_devdata(filp);
- /* return ENODEV if the video device has been removed
- already or if it is not registered anymore. */
- if (vdev == NULL || !video_is_registered(vdev)) {
+ /* return ENODEV if the video device has already been removed. */
+ if (vdev == NULL) {
mutex_unlock(&videodev_lock);
return -ENODEV;
}
/* and increase the device refcount */
video_get(vdev);
mutex_unlock(&videodev_lock);
- if (vdev->fops->open)
- ret = vdev->fops->open(filp);
+ if (vdev->fops->open) {
+ if (vdev->lock)
+ mutex_lock(vdev->lock);
+ if (video_is_registered(vdev))
+ ret = vdev->fops->open(filp);
+ else
+ ret = -ENODEV;
+ if (vdev->lock)
+ mutex_unlock(vdev->lock);
+ }
/* decrease the refcount in case of an error */
if (ret)
@@ -278,8 +313,13 @@
struct video_device *vdev = video_devdata(filp);
int ret = 0;
- if (vdev->fops->release)
+ if (vdev->fops->release) {
+ if (vdev->lock)
+ mutex_lock(vdev->lock);
vdev->fops->release(filp);
+ if (vdev->lock)
+ mutex_unlock(vdev->lock);
+ }
/* decrease the refcount unconditionally since the release()
return value is ignored. */