On Wed, 6 Jul 2011, Éric Piel wrote:
> Hello,
> It seems I'm very unlucky this week and I've come across to what looks
> like a second regression in the kernel. I'm running a version few
> commits after 3.0-rc6, which includes commit e534c5b831c8 "fix
> regression occurring during device removal".
>
> When I plug/unplug/plug a mobile phone, after waiting a few minutes I
> get a "task khubd:621 blocked for more than 120 seconds." Note that it's
> directly connected to my laptop, not via an external hub (although the
> bug also happens with an external hub).
>
> Below is the whole dmesg log (with usb debug messages on)
>
> Let me know if you need me to investigate more, or maybe there is
> already a fix for that bug?
Ah -- this stack dump points out the reason for the hang. It looks
like that "fix regression..." commit didn't go far enough; I neglected
the fact that interfaces can be unbound out of order when a driver
claims multiple interfaces.
Adding this patch on top of that commit should fix this. Let me
know what you both get.
Alan Stern
drivers/usb/core/message.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
Index: usb-3.0/drivers/usb/core/message.c
===================================================================
--- usb-3.0.orig/drivers/usb/core/message.c
+++ usb-3.0/drivers/usb/core/message.c
@@ -1147,6 +1147,14 @@ void usb_disable_device(struct usb_devic
* any drivers bound to them (a key side effect)
*/
if (dev->actconfig) {
+ /*
+ * FIXME: In order to avoid self-deadlock involving the
+ * bandwidth_mutex, we have to mark all the interfaces
+ * before unregistering any of them.
+ */
+ for (i = 0; i < dev->actconfig->desc.bNumInterfaces; i++)
+ dev->actconfig->interface[i]->unregistering = 1;
+
for (i = 0; i < dev->actconfig->desc.bNumInterfaces; i++) {
struct usb_interface *interface;
@@ -1156,7 +1164,6 @@ void usb_disable_device(struct usb_devic
continue;
dev_dbg(&dev->dev, "unregistering interface %s\n",
dev_name(&interface->dev));
- interface->unregistering = 1;
remove_intf_ep_devs(interface);
device_del(&interface->dev);
}
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