USB: fix race in autosuspend reschedule
This patch (as1002) fixes a small race which can occur when a driver
expects usbcore to reschedule an autosuspend request. If the request
arrives too late, it won't be rescheduled. The patch adds an extra
argument to autosuspend_check(), indicating that a reschedule is
needed no matter how much time has elapsed.
It also tries to avoid letting asynchronous changes to the value of
jiffies cause a delay to become negative, by caching a local copy of
the current time.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
index 8c1eac2..c27bc08 100644
--- a/drivers/usb/core/driver.c
+++ b/drivers/usb/core/driver.c
@@ -950,11 +950,11 @@
#ifdef CONFIG_USB_SUSPEND
/* Internal routine to check whether we may autosuspend a device. */
-static int autosuspend_check(struct usb_device *udev)
+static int autosuspend_check(struct usb_device *udev, int reschedule)
{
int i;
struct usb_interface *intf;
- unsigned long suspend_time;
+ unsigned long suspend_time, j;
/* For autosuspend, fail fast if anything is in use or autosuspend
* is disabled. Also fail if any interfaces require remote wakeup
@@ -996,20 +996,20 @@
}
/* If everything is okay but the device hasn't been idle for long
- * enough, queue a delayed autosuspend request.
+ * enough, queue a delayed autosuspend request. If the device
+ * _has_ been idle for long enough and the reschedule flag is set,
+ * likewise queue a delayed (1 second) autosuspend request.
*/
- if (time_after(suspend_time, jiffies)) {
+ j = jiffies;
+ if (time_before(j, suspend_time))
+ reschedule = 1;
+ else
+ suspend_time = j + HZ;
+ if (reschedule) {
if (!timer_pending(&udev->autosuspend.timer)) {
-
- /* The value of jiffies may change between the
- * time_after() comparison above and the subtraction
- * below. That's okay; the system behaves sanely
- * when a timer is registered for the present moment
- * or for the past.
- */
queue_delayed_work(ksuspend_usb_wq, &udev->autosuspend,
- round_jiffies_relative(suspend_time - jiffies));
- }
+ round_jiffies_relative(suspend_time - j));
+ }
return -EAGAIN;
}
return 0;
@@ -1017,7 +1017,7 @@
#else
-static inline int autosuspend_check(struct usb_device *udev)
+static inline int autosuspend_check(struct usb_device *udev, int reschedule)
{
return 0;
}
@@ -1074,7 +1074,7 @@
udev->do_remote_wakeup = device_may_wakeup(&udev->dev);
if (udev->auto_pm) {
- status = autosuspend_check(udev);
+ status = autosuspend_check(udev, 0);
if (status < 0)
goto done;
}
@@ -1100,7 +1100,7 @@
/* Try another autosuspend when the interfaces aren't busy */
if (udev->auto_pm)
- autosuspend_check(udev);
+ autosuspend_check(udev, status == -EBUSY);
/* If the suspend succeeded then prevent any more URB submissions,
* flush any outstanding URBs, and propagate the suspend up the tree.