From aa1b5369ac37acf55783720b9415a5afc2beab50 Mon Sep 17 00:00:00 2001
From: none <git>
Date: Thu, 16 Jan 2020 10:57:53 +0100
Subject: [PATCH] make ddbridge device access count atomic

---
 ddbridge/ddbridge-core.c | 8 +++++---
 ddbridge/ddbridge.h      | 2 +-
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/ddbridge/ddbridge-core.c b/ddbridge/ddbridge-core.c
index 763046c..64150d2 100644
--- a/ddbridge/ddbridge-core.c
+++ b/ddbridge/ddbridge-core.c
@@ -3340,7 +3340,7 @@ static int ddb_release(struct inode *inode, struct file *file)
 {
 	struct ddb *dev = file->private_data;
 
-	dev->ddb_dev_users--;
+	atomic_inc(&dev->ddb_dev_users);
 	return 0;
 }
 
@@ -3348,9 +3348,10 @@ static int ddb_open(struct inode *inode, struct file *file)
 {
 	struct ddb *dev = ddbs[iminor(inode)];
 
-	if (dev->ddb_dev_users)
+	if (!atomic_dec_and_test(&dev->ddb_dev_users)) {
+		atomic_inc(&dev->ddb_dev_users);
 		return -EBUSY;
-	dev->ddb_dev_users++;
+	}
 	file->private_data = dev;
 	return 0;
 }
@@ -4278,6 +4279,7 @@ static int ddb_device_create(struct ddb *dev)
 		return -ENOMEM;
 	mutex_lock(&ddb_mutex);
 	dev->nr = ddb_num;
+	atomic_set(&dev->ddb_dev_users, 1);
 	ddbs[dev->nr] = dev;
 	dev->ddb_dev = device_create(&ddb_class, dev->dev,
 				     MKDEV(ddb_major, dev->nr),
diff --git a/ddbridge/ddbridge.h b/ddbridge/ddbridge.h
index 2416880..370a2ba 100644
--- a/ddbridge/ddbridge.h
+++ b/ddbridge/ddbridge.h
@@ -450,7 +450,7 @@ struct ddb {
 	struct ddb_dma         odma[DDB_MAX_OUTPUT];
 
 	struct device         *ddb_dev;
-	u32                    ddb_dev_users;
+	atomic_t               ddb_dev_users;
 	u32                    nr;
 	u8                     iobuf[1028];