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authorAlan Stern <stern@rowland.harvard.edu>2019-06-25 16:03:58 -0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-06-26 10:28:09 +0800
commitffed60971f3d95923b99ea970862c6ab6a22c20f (patch)
tree295db5fee660d10d63a36be83f17f434bc0bc58c
parent58ee01007c9e00531c1280b2d99b49d29a5e9844 (diff)
USB: core: Remove usbfs_mutex
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@rowland.harvard.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/usb/core/devio.c9
-rw-r--r--drivers/usb/core/notify.c3
-rw-r--r--drivers/usb/core/usb.h1
3 files changed, 0 insertions, 13 deletions
diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
index 186790b06b11..0100a54165cd 100644
--- a/drivers/usb/core/devio.c
+++ b/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 *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;
diff --git a/drivers/usb/core/notify.c b/drivers/usb/core/notify.c
index ab474b11523e..e6143663778f 100644
--- a/drivers/usb/core/notify.c
+++ b/drivers/usb/core/notify.c
@@ -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)
diff --git a/drivers/usb/core/usb.h b/drivers/usb/core/usb.h
index d95a5358f73d..bd8d01f85a13 100644
--- a/drivers/usb/core/usb.h
+++ b/drivers/usb/core/usb.h
@@ -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;