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[PATCH] USB: Add timeout to usb_lock_device_for_reset

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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: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Alan Stern 2005-08-11 10:15:39 -04:00 committed by Greg Kroah-Hartman
parent e52b1d3afe
commit 3ea15966ed
1 changed files with 9 additions and 1 deletions
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10
drivers/usb/core/usb.c
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@ -912,7 +912,7 @@ int usb_trylock_device(struct usb_device *udev)
* is neither BINDING nor BOUND. Rather than sleeping to wait for the
* lock, the routine polls repeatedly. This is to prevent deadlock with
* 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
* 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,
struct usb_interface *iface)
{
unsigned long jiffies_expire = jiffies + HZ;
if (udev->state == USB_STATE_NOTATTACHED)
return -ENODEV;
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)) {
/* 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);
if (udev->state == USB_STATE_NOTATTACHED)
return -ENODEV;