From: Alan Stern Date: Thu, 11 Aug 2005 14:15:39 +0000 (-0400) Subject: [PATCH] USB: Add timeout to usb_lock_device_for_reset X-Git-Tag: v2.6.14-rc1~492^2~18^2~22 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=3ea15966ed59f2bc20928c7b0496b4585f6de206;p=linux-2.6 [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: Alan Stern Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c index bc966dbc60..109f755816 100644 --- a/drivers/usb/core/usb.c +++ b/drivers/usb/core/usb.c @@ -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;