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lock reader, write and user counts with mutex

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internal 2023-11-03 11:21:28 +01:00
parent 05718a5965
commit 948234d787
2 changed files with 21 additions and 7 deletions
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27
dvb-core/dvbdev.c
View File

@ -134,25 +134,35 @@ static struct cdev dvb_device_cdev;
int dvb_generic_open(struct inode *inode, struct file *file)
{
struct dvb_device *dvbdev = file->private_data;
int ret = 0;
if (!dvbdev)
return -ENODEV;
if (!dvbdev->users)
return -EBUSY;
mutex_lock(&dvbdev->lock);
if (!dvbdev->users) {
ret = -EBUSY;
goto unlock;
}
if ((file->f_flags & O_ACCMODE) == O_RDONLY) {
if (!dvbdev->readers)
return -EBUSY;
if (!dvbdev->readers) {
ret = -EBUSY;
goto unlock;
}
dvbdev->readers--;
} else {
if (!dvbdev->writers)
return -EBUSY;
if (!dvbdev->writers) {
ret = -EBUSY;
goto unlock;
}
dvbdev->writers--;
}
dvbdev->users--;
return 0;
unlock:
mutex_unlock(&dvbdev->lock);
return ret;
}
EXPORT_SYMBOL(dvb_generic_open);
@ -163,12 +173,14 @@ int dvb_generic_release(struct inode *inode, struct file *file)
if (!dvbdev)
return -ENODEV;
mutex_lock(&dvbdev->lock);
if ((file->f_flags & O_ACCMODE) == O_RDONLY)
dvbdev->readers++;
else
dvbdev->writers++;
dvbdev->users++;
mutex_unlock(&dvbdev->lock);
dvb_device_put(dvbdev);
@ -524,6 +536,7 @@ int dvb_register_device(struct dvb_adapter *adap, struct dvb_device **pdvbdev,
dvbdev->adapter = adap;
dvbdev->priv = priv;
dvbdev->fops = dvbdevfops;
mutex_init(&dvbdev->lock);
init_waitqueue_head(&dvbdev->wait_queue);
dvbdevfops->owner = adap->module;
list_add_tail(&dvbdev->list_head, &adap->device_list);

1
include/linux/media/dvbdev.h
View File

@ -182,6 +182,7 @@ struct dvb_device {
int readers;
int writers;
int users;
struct mutex lock;
wait_queue_head_t wait_queue;
/* don't really need those !? -- FIXME: use video_usercopy */