Hi, All:
I found (or, rather, our users found and I confirmed) that if a disconnect
happens at the right time, cat /proc/bus/usb/devices is likely to crash.
It can fail in several places, but mostly it's related to a references
to struct usb_device which was freed.
It looks that this problem was addressed in 2.6, but I do not wish to
backport everything. The attached patch makes it to go away in my case.
I suspect that it may be still racy, so I'm pondering if I should send
this to Marcelo. Any comments?
-- Pete
diff -urp -X dontdiff linux-2.4.28-pre3/drivers/usb/devices.c
linux-2.4.28-pre3-usb/drivers/usb/devices.c
--- linux-2.4.28-pre3/drivers/usb/devices.c 2004-09-12 14:24:09.000000000 -0700
+++ linux-2.4.28-pre3-usb/drivers/usb/devices.c 2004-10-05 13:54:14.000000000 -0700
@@ -552,9 +552,13 @@ static ssize_t usb_device_dump(char **bu
/* Now look at all of this device's children. */
for (chix = 0; chix < usbdev->maxchild; chix++) {
- if (usbdev->children[chix]) {
- ret = usb_device_dump(buffer, nbytes, skip_bytes, file_offset,
usbdev->children[chix],
+ struct usb_device *childdev = usbdev->children[chix];
+ if (childdev) {
+ usb_inc_dev_use(childdev);
+ ret = usb_device_dump(buffer, nbytes, skip_bytes,
+ file_offset, childdev,
bus, level + 1, chix, ++cnt);
+ usb_dec_dev_use(childdev);
if (ret == -EFAULT)
return total_written;
total_written += ret;
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