[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 <[EMAIL PROTECTED]>
Signed-off-by: Greg Kroah-Hartman <[EMAIL PROTECTED]>
---
commit 3ea15966ed59f2bc20928c7b0496b4585f6de206
tree 45c392aa393fe4ad245b6593b5a74f212f010637
parent e52b1d3afe698cb77c080ecbe9e745257ff8c81b
author Alan Stern <[EMAIL PROTECTED]> Thu, 11 Aug 2005 10:15:39 -0400
committer Greg Kroah-Hartman <[EMAIL PROTECTED]> Thu, 08 Sep 2005 16:28:21 -0700
drivers/usb/core/usb.c | 10 +++++++++-
1 files changed, 9 insertions(+), 1 deletions(-)
diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
--- a/drivers/usb/core/usb.c
+++ b/drivers/usb/core/usb.c
@@ -912,7 +912,7 @@ int usb_trylock_device(struct usb_device
* 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
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
}
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;
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