This removes the private hiddev_table in the usbhid
driver and changes it to use usb_find_interface
instead.
The advantage is that we can avoid the race between
usb_register_dev and usb_open and no longer need the
big kernel lock.
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Jiri Kosina <jkosina@xxxxxxx>
Cc: "Greg Kroah-Hartman" <gregkh@xxxxxxx>
---
Jiri, this fixes the race you outlined in the comment
and I believe the serialization for the remaining code
should be covered by usb_open taking minor_rwsem.
drivers/hid/usbhid/hiddev.c | 54 +++++++++---------------------------------
1 files changed, 12 insertions(+), 42 deletions(-)
diff --git a/drivers/hid/usbhid/hiddev.c b/drivers/hid/usbhid/hiddev.c
index 39157f3..eee8b13 100644
--- a/drivers/hid/usbhid/hiddev.c
+++ b/drivers/hid/usbhid/hiddev.c
@@ -67,7 +67,7 @@ struct hiddev_list {
struct mutex thread_lock;
};
-static struct hiddev *hiddev_table[HIDDEV_MINORS];
+static struct usb_driver hiddev_driver;
/*
* Find a report, given the report's type and ID. The ID can be specified
@@ -265,22 +265,19 @@ static int hiddev_release(struct inode * inode, struct file * file)
static int hiddev_open(struct inode *inode, struct file *file)
{
struct hiddev_list *list;
- int res, i;
-
- /* See comment in hiddev_connect() for BKL explanation */
- lock_kernel();
- i = iminor(inode) - HIDDEV_MINOR_BASE;
+ struct usb_interface *intf;
+ struct hiddev *hiddev;
+ int res;
- if (i >= HIDDEV_MINORS || i < 0 || !hiddev_table[i])
+ intf = usb_find_interface(&hiddev_driver, iminor(inode));
+ if (!intf)
return -ENODEV;
+ hiddev = usb_get_intfdata(intf);
if (!(list = kzalloc(sizeof(struct hiddev_list), GFP_KERNEL)))
return -ENOMEM;
mutex_init(&list->thread_lock);
-
- list->hiddev = hiddev_table[i];
-
-
+ list->hiddev = hiddev;
file->private_data = list;
/*
@@ -289,7 +286,7 @@ static int hiddev_open(struct inode *inode, struct file *file)
*/
if (list->hiddev->exist) {
if (!list->hiddev->open++) {
- res = usbhid_open(hiddev_table[i]->hid);
+ res = usbhid_open(hiddev->hid);
if (res < 0) {
res = -EIO;
goto bail;
@@ -301,12 +298,12 @@ static int hiddev_open(struct inode *inode, struct file *file)
}
spin_lock_irq(&list->hiddev->list_lock);
- list_add_tail(&list->node, &hiddev_table[i]->list);
+ list_add_tail(&list->node, &hiddev->list);
spin_unlock_irq(&list->hiddev->list_lock);
if (!list->hiddev->open++)
if (list->hiddev->exist) {
- struct hid_device *hid = hiddev_table[i]->hid;
+ struct hid_device *hid = hiddev->hid;
res = usbhid_get_power(hid);
if (res < 0) {
res = -EIO;
@@ -314,13 +311,10 @@ static int hiddev_open(struct inode *inode, struct file *file)
}
usbhid_open(hid);
}
-
- unlock_kernel();
return 0;
bail:
file->private_data = NULL;
kfree(list);
- unlock_kernel();
return res;
}
@@ -895,37 +889,14 @@ int hiddev_connect(struct hid_device *hid, unsigned int force)
hid->hiddev = hiddev;
hiddev->hid = hid;
hiddev->exist = 1;
-
- /*
- * BKL here is used to avoid race after usb_register_dev().
- * Once the device node has been created, open() could happen on it.
- * The code below will then fail, as hiddev_table hasn't been
- * updated.
- *
- * The obvious fix -- introducing mutex to guard hiddev_table[]
- * doesn't work, as usb_open() and usb_register_dev() both take
- * minor_rwsem, thus we'll have ABBA deadlock.
- *
- * Before BKL pushdown, usb_open() had been acquiring it in right
- * order, so _open() was safe to use it to protect from this race.
- * Now the order is different, but AB-BA deadlock still doesn't occur
- * as BKL is dropped on schedule() (i.e. while sleeping on
- * minor_rwsem). Fugly.
- */
- lock_kernel();
+ usb_set_intfdata(usbhid->intf, usbhid);
retval = usb_register_dev(usbhid->intf, &hiddev_class);
if (retval) {
err_hid("Not able to get a minor for this device.");
hid->hiddev = NULL;
- unlock_kernel();
kfree(hiddev);
return -1;
- } else {
- hid->minor = usbhid->intf->minor;
- hiddev_table[usbhid->intf->minor - HIDDEV_MINOR_BASE] = hiddev;
}
- unlock_kernel();
-
return 0;
}
@@ -943,7 +914,6 @@ void hiddev_disconnect(struct hid_device *hid)
hiddev->exist = 0;
mutex_unlock(&hiddev->existancelock);
- hiddev_table[hiddev->hid->minor - HIDDEV_MINOR_BASE] = NULL;
usb_deregister_dev(usbhid->intf, &hiddev_class);
if (hiddev->open) {
--
1.7.1
--
To unsubscribe from this list: send the line "unsubscribe linux-usb" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
