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Commit d1aa3e6a authored by Alan Stern's avatar Alan Stern Committed by Greg Kroah-Hartman
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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: default avatarAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent 58ed7b94

drivers/usb/core/driver.c

+16 −16
Original line number Diff line number Diff line
@@ -950,11 +950,11 @@ static int usb_resume_interface(struct usb_interface *intf, int reset_resume) 
#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
@@ -996,19 +996,19 @@ static int autosuspend_check(struct usb_device *udev) 
	}



	/* 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;

	}
@@ -1017,7 +1017,7 @@ static int autosuspend_check(struct usb_device *udev) 


#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 @@ static int usb_suspend_both(struct usb_device *udev, pm_message_t msg) 
	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 @@ static int usb_suspend_both(struct usb_device *udev, pm_message_t msg) 


		/* 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.