Commit ffed6097 authored by Alan Stern's avatar Alan Stern Committed by Greg Kroah-Hartman
Browse files

USB: core: Remove usbfs_mutex 



Commit 4a2a8a2c ("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: default avatarAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 58ee0100

drivers/usb/core/devio.c

+0 −9
Original line number Diff line number Diff line
@@ -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 *inode, struct file *file) 


	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;

drivers/usb/core/notify.c

+0 −3
Original line number Diff line number Diff line
@@ -53,11 +53,8 @@ void usb_notify_add_device(struct usb_device *udev) 


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)

drivers/usb/core/usb.h

+0 −1
Original line number Diff line number Diff line
@@ -169,7 +169,6 @@ extern const struct attribute_group *usb_device_groups[]; 
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;

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