Commit 62e299e6 authored by Alan Stern's avatar Alan Stern Committed by Greg Kroah-Hartman

USB: change locking for device-level autosuspend

This patch (as1323) changes the locking requirements for
usb_autosuspend_device(), usb_autoresume_device(), and
usb_try_autosuspend_device().  This isn't a very important change;
mainly it's meant to make the locking more uniform.

The most tricky part of the patch involves changes to usbdev_open().
To avoid an ABBA locking problem, it was necessary to reduce the
region protected by usbfs_mutex.  Since that mutex now protects only
against simultaneous open and remove, this posed no difficulty -- its
scope was larger than necessary.

And it turns out that usbfs_mutex is no longer needed in
usbdev_release() at all.  The list of usbfs "ps" structures is now
protected by the device lock instead of by usbfs_mutex.
Signed-off-by: default avatarAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent 0f3dda9f
......@@ -654,19 +654,21 @@ static int usbdev_open(struct inode *inode, struct file *file)
int ret;
lock_kernel();
/* Protect against simultaneous removal or release */
mutex_lock(&usbfs_mutex);
ret = -ENOMEM;
ps = kmalloc(sizeof(struct dev_state), GFP_KERNEL);
if (!ps)
goto out;
goto out_free_ps;
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);
#ifdef CONFIG_USB_DEVICEFS
/* procfs file */
if (!dev) {
......@@ -678,13 +680,19 @@ static int usbdev_open(struct inode *inode, struct file *file)
dev = NULL;
}
#endif
if (!dev || dev->state == USB_STATE_NOTATTACHED)
goto out;
mutex_unlock(&usbfs_mutex);
if (!dev)
goto out_free_ps;
usb_lock_device(dev);
if (dev->state == USB_STATE_NOTATTACHED)
goto out_unlock_device;
ret = usb_autoresume_device(dev);
if (ret)
goto out;
goto out_unlock_device;
ret = 0;
ps->dev = dev;
ps->file = file;
spin_lock_init(&ps->lock);
......@@ -702,14 +710,17 @@ static int usbdev_open(struct inode *inode, struct file *file)
smp_wmb();
list_add_tail(&ps->list, &dev->filelist);
file->private_data = ps;
usb_unlock_device(dev);
snoop(&dev->dev, "opened by process %d: %s\n", task_pid_nr(current),
current->comm);
out:
if (ret) {
kfree(ps);
unlock_kernel();
return ret;
out_unlock_device:
usb_unlock_device(dev);
usb_put_dev(dev);
}
mutex_unlock(&usbfs_mutex);
out_free_ps:
kfree(ps);
unlock_kernel();
return ret;
}
......@@ -724,10 +735,7 @@ static int usbdev_release(struct inode *inode, struct file *file)
usb_lock_device(dev);
usb_hub_release_all_ports(dev, ps);
/* Protect against simultaneous open */
mutex_lock(&usbfs_mutex);
list_del_init(&ps->list);
mutex_unlock(&usbfs_mutex);
for (ifnum = 0; ps->ifclaimed && ifnum < 8*sizeof(ps->ifclaimed);
ifnum++) {
......
......@@ -1478,8 +1478,7 @@ void usb_autoresume_work(struct work_struct *work)
* driver requires remote-wakeup capability during autosuspend but remote
* wakeup is disabled, the autosuspend will fail.
*
* Often the caller will hold @udev's device lock, but this is not
* necessary.
* The caller must hold @udev's device lock.
*
* This routine can run only in process context.
*/
......@@ -1503,6 +1502,8 @@ void usb_autosuspend_device(struct usb_device *udev)
* for an active interface is greater than 0, or autosuspend is not allowed
* for any other reason, no autosuspend request will be queued.
*
* The caller must hold @udev's device lock.
*
* This routine can run only in process context.
*/
void usb_try_autosuspend_device(struct usb_device *udev)
......@@ -1526,8 +1527,7 @@ void usb_try_autosuspend_device(struct usb_device *udev)
* @udev's usage counter is incremented to prevent subsequent autosuspends.
* However if the autoresume fails then the usage counter is re-decremented.
*
* Often the caller will hold @udev's device lock, but this is not
* necessary (and attempting it might cause deadlock).
* The caller must hold @udev's device lock.
*
* This routine can run only in process context.
*/
......
......@@ -352,6 +352,7 @@ set_autosuspend(struct device *dev, struct device_attribute *attr,
return -EINVAL;
value *= HZ;
usb_lock_device(udev);
udev->autosuspend_delay = value;
if (value >= 0)
usb_try_autosuspend_device(udev);
......@@ -359,6 +360,7 @@ set_autosuspend(struct device *dev, struct device_attribute *attr,
if (usb_autoresume_device(udev) == 0)
usb_autosuspend_device(udev);
}
usb_unlock_device(udev);
return count;
}
......
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