We're holding the global wdm_mutex through most of wdm_open, including
when it calls usb_autopm_get_interface. This call can block waiting for
a resume, which will need to look up the device list. So we deadlock.
Fix by using a dedicated lock for the device list.
Signed-off-by: Bjørn Mork <bjorn@xxxxxxx>
---
v2: A spinlock makes more sense here, as pointed out by Oliver Neukum
drivers/usb/class/cdc-wdm.c | 14 +++++++++-----
1 files changed, 9 insertions(+), 5 deletions(-)
diff --git a/drivers/usb/class/cdc-wdm.c b/drivers/usb/class/cdc-wdm.c
index 9f2cfb5..70197de 100644
--- a/drivers/usb/class/cdc-wdm.c
+++ b/drivers/usb/class/cdc-wdm.c
@@ -78,6 +78,7 @@ MODULE_DEVICE_TABLE (usb, wdm_ids);
#define WDM_DEFAULT_BUFSIZE 256
static DEFINE_MUTEX(wdm_mutex);
+static DEFINE_SPINLOCK(wdm_device_list_lock);
static LIST_HEAD(wdm_device_list);
/* --- method tables --- */
@@ -124,23 +125,24 @@ static struct wdm_device *wdm_find_device(struct usb_interface *intf)
{
struct wdm_device *desc = NULL;
- mutex_lock(&wdm_mutex);
+ spin_lock(&wdm_device_list_lock);
list_for_each_entry(desc, &wdm_device_list, device_list)
if (desc->intf == intf)
break;
- mutex_unlock(&wdm_mutex);
+ spin_unlock(&wdm_device_list_lock);
return desc;
}
-/* caller holds wdm_mutex */
static struct wdm_device *wdm_find_device_by_minor(int minor)
{
struct wdm_device *desc = NULL;
+ spin_lock(&wdm_device_list_lock);
list_for_each_entry(desc, &wdm_device_list, device_list)
if (desc->intf->minor == minor)
break;
+ spin_unlock(&wdm_device_list_lock);
return desc;
}
@@ -304,7 +306,9 @@ static void free_urbs(struct wdm_device *desc)
static void cleanup(struct wdm_device *desc)
{
+ spin_lock(&wdm_device_list_lock);
list_del(&desc->device_list);
+ spin_unlock(&wdm_device_list_lock);
kfree(desc->sbuf);
kfree(desc->inbuf);
kfree(desc->orq);
@@ -733,9 +737,9 @@ static int wdm_create(struct usb_interface *intf, struct usb_endpoint_descriptor
desc
);
- mutex_lock(&wdm_mutex);
+ spin_lock(&wdm_device_list_lock);
list_add(&desc->device_list, &wdm_device_list);
- mutex_unlock(&wdm_mutex);
+ spin_unlock(&wdm_device_list_lock);
rv = usb_register_dev(intf, &wdm_class);
if (rv < 0)
--
1.7.8.3
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