Commit 4a2a8a2cce86 ("usbfs: private mutex for open, release, and
remove") is now obsolete. The commit was created back when we had
to handle both usbfs device nodes and the old usbdevfs filesystem
(/proc/bus/usb/), but usbdevfs no longer exists.
This means there's no longer any need to hold a mutex during two
separate removal operations (and thus during an entire notifier chain
call). Furthermore, the one remaining remove/release pair doesn't
race with open thanks to the synchronization provided by the device
model core in bus_find_device(). Remove and release don't race with
each other because they both run with the device lock held.
The upshot is that usbfs_mutex isn't needed any more. This patch
removes it entirely.
Signed-off-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
---
[as1904]
drivers/usb/core/devio.c | 9 ---------
drivers/usb/core/notify.c | 3 ---
drivers/usb/core/usb.h | 1 -
3 files changed, 13 deletions(-)
Index: usb-devel/drivers/usb/core/devio.c
===================================================================
--- usb-devel.orig/drivers/usb/core/devio.c
+++ usb-devel/drivers/usb/core/devio.c
@@ -48,9 +48,6 @@
#define USB_DEVICE_MAX (USB_MAXBUS * 128)
#define USB_SG_SIZE 16384 /* split-size for large txs */
-/* Mutual exclusion for removal, open, and release */
-DEFINE_MUTEX(usbfs_mutex);
-
struct usb_dev_state {
struct list_head list; /* state list */
struct usb_device *dev;
@@ -979,15 +976,9 @@ static int usbdev_open(struct inode *ino
ret = -ENODEV;
- /* Protect against simultaneous removal or release */
- mutex_lock(&usbfs_mutex);
-
/* usbdev device-node */
if (imajor(inode) == USB_DEVICE_MAJOR)
dev = usbdev_lookup_by_devt(inode->i_rdev);
-
- mutex_unlock(&usbfs_mutex);
-
if (!dev)
goto out_free_ps;
Index: usb-devel/drivers/usb/core/notify.c
===================================================================
--- usb-devel.orig/drivers/usb/core/notify.c
+++ usb-devel/drivers/usb/core/notify.c
@@ -53,11 +53,8 @@ void usb_notify_add_device(struct usb_de
void usb_notify_remove_device(struct usb_device *udev)
{
- /* Protect against simultaneous usbfs open */
- mutex_lock(&usbfs_mutex);
blocking_notifier_call_chain(&usb_notifier_list,
USB_DEVICE_REMOVE, udev);
- mutex_unlock(&usbfs_mutex);
}
void usb_notify_add_bus(struct usb_bus *ubus)
Index: usb-devel/drivers/usb/core/usb.h
===================================================================
--- usb-devel.orig/drivers/usb/core/usb.h
+++ usb-devel/drivers/usb/core/usb.h
@@ -169,7 +169,6 @@ extern const struct attribute_group *usb
extern const struct attribute_group *usb_interface_groups[];
/* usbfs stuff */
-extern struct mutex usbfs_mutex;
extern struct usb_driver usbfs_driver;
extern const struct file_operations usbfs_devices_fops;
extern const struct file_operations usbdev_file_operations;
