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synced 2024-10-03 15:47:36 +00:00
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>
This commit is contained in:
parent
c29fcff3da
commit
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4 changed files with 89 additions and 19 deletions
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@ -453,6 +453,10 @@ You should also set these fields:
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- ioctl_ops: if you use the v4l2_ioctl_ops to simplify ioctl maintenance
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- ioctl_ops: if you use the v4l2_ioctl_ops to simplify ioctl maintenance
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(highly recommended to use this and it might become compulsory in the
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(highly recommended to use this and it might become compulsory in the
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future!), then set this to your v4l2_ioctl_ops struct.
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future!), then set this to your v4l2_ioctl_ops struct.
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- lock: leave to NULL if you want to do all the locking in the driver.
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Otherwise you give it a pointer to a struct mutex_lock and before any
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of the v4l2_file_operations is called this lock will be taken by the
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core and released afterwards.
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- parent: you only set this if v4l2_device was registered with NULL as
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- parent: you only set this if v4l2_device was registered with NULL as
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the parent device struct. This only happens in cases where one hardware
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the parent device struct. This only happens in cases where one hardware
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device has multiple PCI devices that all share the same v4l2_device core.
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device has multiple PCI devices that all share the same v4l2_device core.
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@ -469,6 +473,22 @@ If you use v4l2_ioctl_ops, then you should set either .unlocked_ioctl or
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The v4l2_file_operations struct is a subset of file_operations. The main
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The v4l2_file_operations struct is a subset of file_operations. The main
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difference is that the inode argument is omitted since it is never used.
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difference is that the inode argument is omitted since it is never used.
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v4l2_file_operations and locking
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--------------------------------
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You can set a pointer to a mutex_lock in struct video_device. Usually this
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will be either a top-level mutex or a mutex per device node. If you want
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finer-grained locking then you have to set it to NULL and do you own locking.
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If a lock is specified then all file operations will be serialized on that
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lock. If you use videobuf then you must pass the same lock to the videobuf
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queue initialize function: if videobuf has to wait for a frame to arrive, then
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it will temporarily unlock the lock and relock it afterwards. If your driver
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also waits in the code, then you should do the same to allow other processes
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to access the device node while the first process is waiting for something.
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The implementation of a hotplug disconnect should also take the lock before
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calling v4l2_device_disconnect and video_unregister_device.
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video_device registration
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video_device registration
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-------------------------
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-------------------------
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@ -187,33 +187,50 @@ static ssize_t v4l2_read(struct file *filp, char __user *buf,
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size_t sz, loff_t *off)
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size_t sz, loff_t *off)
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{
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{
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struct video_device *vdev = video_devdata(filp);
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struct video_device *vdev = video_devdata(filp);
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int ret = -EIO;
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if (!vdev->fops->read)
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if (!vdev->fops->read)
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return -EINVAL;
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return -EINVAL;
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if (!video_is_registered(vdev))
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if (vdev->lock)
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return -EIO;
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mutex_lock(vdev->lock);
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return vdev->fops->read(filp, buf, sz, off);
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if (video_is_registered(vdev))
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ret = vdev->fops->read(filp, buf, sz, off);
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if (vdev->lock)
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mutex_unlock(vdev->lock);
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return ret;
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}
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}
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static ssize_t v4l2_write(struct file *filp, const char __user *buf,
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static ssize_t v4l2_write(struct file *filp, const char __user *buf,
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size_t sz, loff_t *off)
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size_t sz, loff_t *off)
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{
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{
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struct video_device *vdev = video_devdata(filp);
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struct video_device *vdev = video_devdata(filp);
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int ret = -EIO;
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if (!vdev->fops->write)
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if (!vdev->fops->write)
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return -EINVAL;
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return -EINVAL;
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if (!video_is_registered(vdev))
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if (vdev->lock)
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return -EIO;
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mutex_lock(vdev->lock);
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return vdev->fops->write(filp, buf, sz, off);
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if (video_is_registered(vdev))
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ret = vdev->fops->write(filp, buf, sz, off);
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if (vdev->lock)
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mutex_unlock(vdev->lock);
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return ret;
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}
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}
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static unsigned int v4l2_poll(struct file *filp, struct poll_table_struct *poll)
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static unsigned int v4l2_poll(struct file *filp, struct poll_table_struct *poll)
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{
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{
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struct video_device *vdev = video_devdata(filp);
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struct video_device *vdev = video_devdata(filp);
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int ret = DEFAULT_POLLMASK;
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if (!vdev->fops->poll || !video_is_registered(vdev))
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if (!vdev->fops->poll)
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return DEFAULT_POLLMASK;
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return ret;
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return vdev->fops->poll(filp, poll);
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if (vdev->lock)
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mutex_lock(vdev->lock);
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if (video_is_registered(vdev))
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ret = vdev->fops->poll(filp, poll);
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if (vdev->lock)
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mutex_unlock(vdev->lock);
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return ret;
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}
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}
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static long v4l2_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
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static long v4l2_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
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@ -224,7 +241,11 @@ static long v4l2_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
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if (!vdev->fops->ioctl)
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if (!vdev->fops->ioctl)
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return -ENOTTY;
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return -ENOTTY;
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if (vdev->fops->unlocked_ioctl) {
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if (vdev->fops->unlocked_ioctl) {
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if (vdev->lock)
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mutex_lock(vdev->lock);
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ret = vdev->fops->unlocked_ioctl(filp, cmd, arg);
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ret = vdev->fops->unlocked_ioctl(filp, cmd, arg);
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if (vdev->lock)
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mutex_unlock(vdev->lock);
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} else if (vdev->fops->ioctl) {
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} else if (vdev->fops->ioctl) {
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/* TODO: convert all drivers to unlocked_ioctl */
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/* TODO: convert all drivers to unlocked_ioctl */
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lock_kernel();
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lock_kernel();
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@ -239,10 +260,17 @@ static long v4l2_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
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static int v4l2_mmap(struct file *filp, struct vm_area_struct *vm)
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static int v4l2_mmap(struct file *filp, struct vm_area_struct *vm)
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{
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{
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struct video_device *vdev = video_devdata(filp);
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struct video_device *vdev = video_devdata(filp);
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int ret = -ENODEV;
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if (!vdev->fops->mmap || !video_is_registered(vdev))
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if (!vdev->fops->mmap)
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return -ENODEV;
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return ret;
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return vdev->fops->mmap(filp, vm);
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if (vdev->lock)
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mutex_lock(vdev->lock);
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if (video_is_registered(vdev))
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ret = vdev->fops->mmap(filp, vm);
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if (vdev->lock)
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mutex_unlock(vdev->lock);
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return ret;
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}
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}
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/* Override for the open function */
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/* Override for the open function */
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@ -254,17 +282,24 @@ static int v4l2_open(struct inode *inode, struct file *filp)
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/* Check if the video device is available */
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/* Check if the video device is available */
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mutex_lock(&videodev_lock);
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mutex_lock(&videodev_lock);
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vdev = video_devdata(filp);
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vdev = video_devdata(filp);
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/* return ENODEV if the video device has been removed
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/* return ENODEV if the video device has already been removed. */
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already or if it is not registered anymore. */
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if (vdev == NULL) {
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if (vdev == NULL || !video_is_registered(vdev)) {
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mutex_unlock(&videodev_lock);
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mutex_unlock(&videodev_lock);
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return -ENODEV;
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return -ENODEV;
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}
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}
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/* and increase the device refcount */
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/* and increase the device refcount */
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video_get(vdev);
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video_get(vdev);
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mutex_unlock(&videodev_lock);
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mutex_unlock(&videodev_lock);
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if (vdev->fops->open)
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if (vdev->fops->open) {
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ret = vdev->fops->open(filp);
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if (vdev->lock)
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mutex_lock(vdev->lock);
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if (video_is_registered(vdev))
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ret = vdev->fops->open(filp);
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else
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ret = -ENODEV;
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if (vdev->lock)
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mutex_unlock(vdev->lock);
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}
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/* decrease the refcount in case of an error */
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/* decrease the refcount in case of an error */
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if (ret)
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if (ret)
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@ -278,8 +313,13 @@ static int v4l2_release(struct inode *inode, struct file *filp)
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struct video_device *vdev = video_devdata(filp);
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struct video_device *vdev = video_devdata(filp);
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int ret = 0;
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int ret = 0;
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if (vdev->fops->release)
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if (vdev->fops->release) {
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if (vdev->lock)
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mutex_lock(vdev->lock);
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vdev->fops->release(filp);
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vdev->fops->release(filp);
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if (vdev->lock)
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mutex_unlock(vdev->lock);
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}
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/* decrease the refcount unconditionally since the release()
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/* decrease the refcount unconditionally since the release()
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return value is ignored. */
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return value is ignored. */
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@ -134,15 +134,22 @@ int v4l2_event_dequeue(struct v4l2_fh *fh, struct v4l2_event *event,
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if (nonblocking)
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if (nonblocking)
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return __v4l2_event_dequeue(fh, event);
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return __v4l2_event_dequeue(fh, event);
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/* Release the vdev lock while waiting */
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if (fh->vdev->lock)
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mutex_unlock(fh->vdev->lock);
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do {
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do {
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ret = wait_event_interruptible(events->wait,
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ret = wait_event_interruptible(events->wait,
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events->navailable != 0);
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events->navailable != 0);
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if (ret < 0)
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if (ret < 0)
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return ret;
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break;
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ret = __v4l2_event_dequeue(fh, event);
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ret = __v4l2_event_dequeue(fh, event);
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} while (ret == -ENOENT);
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} while (ret == -ENOENT);
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if (fh->vdev->lock)
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mutex_lock(fh->vdev->lock);
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return ret;
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return ret;
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}
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}
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EXPORT_SYMBOL_GPL(v4l2_event_dequeue);
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EXPORT_SYMBOL_GPL(v4l2_event_dequeue);
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@ -94,6 +94,9 @@ struct video_device
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/* ioctl callbacks */
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/* ioctl callbacks */
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const struct v4l2_ioctl_ops *ioctl_ops;
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const struct v4l2_ioctl_ops *ioctl_ops;
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/* serialization lock */
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struct mutex *lock;
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};
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};
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/* dev to video-device */
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/* dev to video-device */
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