[media] cx88: protect cx8802_devlist with a mutex

Add and use a mutex to protect the cx88-mpeg device list.  Previously
the BKL prevented races.

Based on work by Ben Hutchings <ben@decadent.org.uk>.

Tested-by: Andi Huber <hobrom@gmx.at>
Tested-by: Marlon de Boer <marlon@hyves.nl>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 17 insertions, 3 deletions

diff --git a/drivers/media/video/cx88/cx88-mpeg.c b/drivers/media/video/cx88/cx88-mpeg.c
index 455290011d4e..1a7b983f8297 100644
--- a/drivers/media/video/cx88/cx88-mpeg.c
+++ b/drivers/media/video/cx88/cx88-mpeg.c
@@ -78,6 +78,7 @@ static void flush_request_modules(struct cx8802_dev *dev)
 
 
 static LIST_HEAD(cx8802_devlist);
+static DEFINE_MUTEX(cx8802_mutex);
 /* ------------------------------------------------------------------ */
 
 static int cx8802_start_dma(struct cx8802_dev    *dev,
@@ -689,6 +690,8 @@ int cx8802_register_driver(struct cx8802_driver *drv)
                 return err;
         }
 
+        mutex_lock(&cx8802_mutex);
+
         list_for_each_entry(dev, &cx8802_devlist, devlist) {
                 printk(KERN_INFO
                        "%s/2: subsystem: %04x:%04x, board: %s [card=%d]\n",
@@ -698,8 +701,10 @@ int cx8802_register_driver(struct cx8802_driver *drv)
 
                 /* Bring up a new struct for each driver instance */
                 driver = kzalloc(sizeof(*drv),GFP_KERNEL);
-                if (driver == NULL)
-                        return -ENOMEM;
+                if (driver == NULL) {
+                        err = -ENOMEM;
+                        goto out;
+                }
 
                 /* Snapshot of the driver registration data */
                 drv->core = dev->core;
@@ -722,7 +727,10 @@ int cx8802_register_driver(struct cx8802_driver *drv)
                 mutex_unlock(&drv->core->lock);
         }
 
-        return i ? 0 : -ENODEV;
+        err = i ? 0 : -ENODEV;
+out:
+        mutex_unlock(&cx8802_mutex);
+        return err;
 }
 
 int cx8802_unregister_driver(struct cx8802_driver *drv)
@@ -736,6 +744,8 @@ int cx8802_unregister_driver(struct cx8802_driver *drv)
                drv->type_id == CX88_MPEG_DVB ? "dvb" : "blackbird",
                drv->hw_access == CX8802_DRVCTL_SHARED ? "shared" : "exclusive");
 
+        mutex_lock(&cx8802_mutex);
+
         list_for_each_entry(dev, &cx8802_devlist, devlist) {
                 printk(KERN_INFO
                        "%s/2: subsystem: %04x:%04x, board: %s [card=%d]\n",
@@ -762,6 +772,8 @@ int cx8802_unregister_driver(struct cx8802_driver *drv)
                 mutex_unlock(&dev->core->lock);
         }
 
+        mutex_unlock(&cx8802_mutex);
+
         return err;
 }
 
@@ -799,7 +811,9 @@ static int __devinit cx8802_probe(struct pci_dev *pci_dev,
                 goto fail_free;
 
         INIT_LIST_HEAD(&dev->drvlist);
+        mutex_lock(&cx8802_mutex);
         list_add_tail(&dev->devlist,&cx8802_devlist);
+        mutex_unlock(&cx8802_mutex);
 
         /* now autoload cx88-dvb or cx88-blackbird */
         request_modules(dev);