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authorJonathan Nieder <jrnieder@gmail.com>2011-05-01 06:29:16 -0300
committerGreg Kroah-Hartman <gregkh@suse.de>2011-06-03 10:34:28 +0900
commit18dc0de0c7e41be4fe0ca22c6aa384cc38fa45d5 (patch)
treec3d125e72d63dea3b4666b147e8b73ef64765219
parentd8fe0246330b97a736c7c9986c70eadc7b014581 (diff)
downloadlinux-linaro-stable-18dc0de0c7e41be4fe0ca22c6aa384cc38fa45d5.tar.gz
cx88: protect per-device driver list with device lock
commit 8a317a8760cfffa8185b56ff59fb4b6c58488d79 upstream. The BKL conversion of this driver seems to have gone wrong. Various uses of the sub-device and driver lists appear to be subject to race conditions. In particular, some functions access drvlist without a relevant lock held, which will race against removal of drivers. Let's start with that --- clean up by consistently protecting dev->drvlist with dev->core->lock, noting driver functions that require the device lock to be held or not to be held. After this patch, there are still some races --- e.g., cx8802_blackbird_remove can run between the time the blackbird driver is acquired and the time it is used in mpeg_release, and there's a similar race in cx88_dvb_bus_ctrl. Later patches will address the remaining known races and the deadlock noticed by Andi. This patch just makes the semantics clearer in preparation for those later changes. 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> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r--drivers/media/video/cx88/cx88-blackbird.c3
-rw-r--r--drivers/media/video/cx88/cx88-dvb.c3
-rw-r--r--drivers/media/video/cx88/cx88-mpeg.c11
-rw-r--r--drivers/media/video/cx88/cx88.h9
4 files changed, 20 insertions, 6 deletions
diff --git a/drivers/media/video/cx88/cx88-blackbird.c b/drivers/media/video/cx88/cx88-blackbird.c
index bca307eb1e24..b93fbd39a39e 100644
--- a/drivers/media/video/cx88/cx88-blackbird.c
+++ b/drivers/media/video/cx88/cx88-blackbird.c
@@ -1122,10 +1122,11 @@ static int mpeg_release(struct file *file)
mutex_lock(&dev->core->lock);
file->private_data = NULL;
kfree(fh);
- mutex_unlock(&dev->core->lock);
/* Make sure we release the hardware */
drv = cx8802_get_driver(dev, CX88_MPEG_BLACKBIRD);
+ mutex_unlock(&dev->core->lock);
+
if (drv)
drv->request_release(drv);
diff --git a/drivers/media/video/cx88/cx88-dvb.c b/drivers/media/video/cx88/cx88-dvb.c
index 90717ee944ec..88a15079ef2f 100644
--- a/drivers/media/video/cx88/cx88-dvb.c
+++ b/drivers/media/video/cx88/cx88-dvb.c
@@ -132,7 +132,10 @@ static int cx88_dvb_bus_ctrl(struct dvb_frontend* fe, int acquire)
return -EINVAL;
}
+ mutex_lock(&dev->core->lock);
drv = cx8802_get_driver(dev, CX88_MPEG_DVB);
+ mutex_unlock(&dev->core->lock);
+
if (drv) {
if (acquire){
dev->frontends.active_fe_id = fe_id;
diff --git a/drivers/media/video/cx88/cx88-mpeg.c b/drivers/media/video/cx88/cx88-mpeg.c
index addf9545e9bf..918172b87148 100644
--- a/drivers/media/video/cx88/cx88-mpeg.c
+++ b/drivers/media/video/cx88/cx88-mpeg.c
@@ -748,6 +748,8 @@ int cx8802_unregister_driver(struct cx8802_driver *drv)
dev->pci->subsystem_device, dev->core->board.name,
dev->core->boardnr);
+ mutex_lock(&dev->core->lock);
+
list_for_each_entry_safe(d, dtmp, &dev->drvlist, drvlist) {
/* only unregister the correct driver type */
if (d->type_id != drv->type_id)
@@ -755,15 +757,14 @@ int cx8802_unregister_driver(struct cx8802_driver *drv)
err = d->remove(d);
if (err == 0) {
- mutex_lock(&drv->core->lock);
list_del(&d->drvlist);
- mutex_unlock(&drv->core->lock);
kfree(d);
} else
printk(KERN_ERR "%s/2: cx8802 driver remove "
"failed (%d)\n", dev->core->name, err);
}
+ mutex_unlock(&dev->core->lock);
}
return err;
@@ -827,6 +828,8 @@ static void __devexit cx8802_remove(struct pci_dev *pci_dev)
flush_request_modules(dev);
+ mutex_lock(&dev->core->lock);
+
if (!list_empty(&dev->drvlist)) {
struct cx8802_driver *drv, *tmp;
int err;
@@ -838,9 +841,7 @@ static void __devexit cx8802_remove(struct pci_dev *pci_dev)
list_for_each_entry_safe(drv, tmp, &dev->drvlist, drvlist) {
err = drv->remove(drv);
if (err == 0) {
- mutex_lock(&drv->core->lock);
list_del(&drv->drvlist);
- mutex_unlock(&drv->core->lock);
} else
printk(KERN_ERR "%s/2: cx8802 driver remove "
"failed (%d)\n", dev->core->name, err);
@@ -848,6 +849,8 @@ static void __devexit cx8802_remove(struct pci_dev *pci_dev)
}
}
+ mutex_unlock(&dev->core->lock);
+
/* Destroy any 8802 reference. */
dev->core->dvbdev = NULL;
diff --git a/drivers/media/video/cx88/cx88.h b/drivers/media/video/cx88/cx88.h
index c9981e77416a..6ff34c711b00 100644
--- a/drivers/media/video/cx88/cx88.h
+++ b/drivers/media/video/cx88/cx88.h
@@ -496,7 +496,11 @@ struct cx8802_driver {
int (*resume)(struct pci_dev *pci_dev);
/* MPEG 8802 -> mini driver - Driver probe and configuration */
+
+ /* Caller must _not_ hold core->lock */
int (*probe)(struct cx8802_driver *drv);
+
+ /* Caller must hold core->lock */
int (*remove)(struct cx8802_driver *drv);
/* MPEG 8802 -> mini driver - Access for hardware control */
@@ -551,8 +555,9 @@ struct cx8802_dev {
/* for switching modulation types */
unsigned char ts_gen_cntrl;
- /* List of attached drivers */
+ /* List of attached drivers; must hold core->lock to access */
struct list_head drvlist;
+
struct work_struct request_module_wk;
};
@@ -675,6 +680,8 @@ int cx88_audio_thread(void *data);
int cx8802_register_driver(struct cx8802_driver *drv);
int cx8802_unregister_driver(struct cx8802_driver *drv);
+
+/* Caller must hold core->lock */
struct cx8802_driver * cx8802_get_driver(struct cx8802_dev *dev, enum cx88_board_type btype);
/* ----------------------------------------------------------- */