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Commit 3ea15966 authored by Alan Stern's avatar Alan Stern Committed by Greg Kroah-Hartman
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[PATCH] USB: Add timeout to usb_lock_device_for_reset 



This patch (as555) modifies the already-awkward
usb_lock_device_for_reset routine in usbcore by adding a timeout.  The
whole point of the routine is that the caller wants to acquire some
semaphores in the wrong order; protecting against the possibility of
deadlock by timing out seems only prudent.

Signed-off-by: default avatarAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent e52b1d3a

drivers/usb/core/usb.c

+9 −1
Original line number Original line Diff line number Diff line
@@ -912,7 +912,7 @@ int usb_trylock_device(struct usb_device *udev) 
 * is neither BINDING nor BOUND.  Rather than sleeping to wait for the

 * is neither BINDING nor BOUND.  Rather than sleeping to wait for the

 * lock, the routine polls repeatedly.  This is to prevent deadlock with

 * lock, the routine polls repeatedly.  This is to prevent deadlock with

 * disconnect; in some drivers (such as usb-storage) the disconnect()

 * disconnect; in some drivers (such as usb-storage) the disconnect()

 * callback will block waiting for a device reset to complete.

 * or suspend() method will block waiting for a device reset to complete.

 *

 *

 * Returns a negative error code for failure, otherwise 1 or 0 to indicate

 * Returns a negative error code for failure, otherwise 1 or 0 to indicate

 * that the device will or will not have to be unlocked.  (0 can be

 * that the device will or will not have to be unlocked.  (0 can be
@@ -922,6 +922,8 @@ int usb_trylock_device(struct usb_device *udev) 
int usb_lock_device_for_reset(struct usb_device *udev,

int usb_lock_device_for_reset(struct usb_device *udev,

		struct usb_interface *iface)

		struct usb_interface *iface)

{

{

	unsigned long jiffies_expire = jiffies + HZ;



	if (udev->state == USB_STATE_NOTATTACHED)

	if (udev->state == USB_STATE_NOTATTACHED)

		return -ENODEV;

		return -ENODEV;

	if (udev->state == USB_STATE_SUSPENDED)

	if (udev->state == USB_STATE_SUSPENDED)
@@ -938,6 +940,12 @@ int usb_lock_device_for_reset(struct usb_device *udev, 
	}

	}





	while (!usb_trylock_device(udev)) {

	while (!usb_trylock_device(udev)) {



		/* If we can't acquire the lock after waiting one second,

		 * we're probably deadlocked */

		if (time_after(jiffies, jiffies_expire))

			return -EBUSY;



		msleep(15);

		msleep(15);

		if (udev->state == USB_STATE_NOTATTACHED)

		if (udev->state == USB_STATE_NOTATTACHED)

			return -ENODEV;

			return -ENODEV;