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: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/drivers/usb/core/sysfs.c b/drivers/usb/core/sysfs.c
index 1b3c00b..d8f3bfe 100644
--- a/drivers/usb/core/sysfs.c
+++ b/drivers/usb/core/sysfs.c
@@ -352,6 +352,7 @@
return -EINVAL;
value *= HZ;
+ usb_lock_device(udev);
udev->autosuspend_delay = value;
if (value >= 0)
usb_try_autosuspend_device(udev);
@@ -359,6 +360,7 @@
if (usb_autoresume_device(udev) == 0)
usb_autosuspend_device(udev);
}
+ usb_unlock_device(udev);
return count;
}