Re: Bug 153551: Kernel panic on Nexus 5X USB unplug while tethering

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On 08/25/2016 05:09 AM, Mathias Nyman wrote:
On 24.08.2016 17:14, Alan Stern wrote:
On Wed, 24 Aug 2016, Mathias Nyman wrote:

The sleep() worked as it delayed freeing the primary hcd, changing the
order to first release usb3 hcd and then usb2 hcd.

Does this mean that the patch you already posted is the proper fix?

Not sure, still just a step in the right direction.
"ab2a4bf USB: don't free bandwidth_mutex too early" seems to solve the
other DELL XPS mass storage remove bug.

This Nexus 5 case still shows a locking issue after my patch. It ran a
4.7.2 kernel which should have your fix
included.

Jose Marino, could you try the patch on top of latest 4.8-rc3, just to
make sure it's not some old issue?

About the locking issue, looks like we end up waiting forever for the
device lock mutex:

[  240.854069] INFO: task kworker/u16:31:970 blocked for more than 120
seconds.
[  240.854070]       Tainted: G        W  O    4.7.2-1-jose #1
[  240.854074] Workqueue: kacpi_hotplug acpi_hotplug_work_fn
[  240.854076] Call Trace:
[  240.854077]  [<ffffffff815d31ec>] schedule+0x3c/0x90
[  240.854078]  [<ffffffff815d3595>] schedule_preempt_disabled+0x15/0x20
[  240.854080]  [<ffffffff815d4a5e>] __mutex_lock_slowpath+0xce/0x140
[  240.854082]  [<ffffffff815d4ae7>] mutex_lock+0x17/0x30
[  240.854085]  [<ffffffffa007c001>] usb_disconnect+0x51/0x2a0 [usbcore]
[  240.854087]  [<ffffffffa0082877>] usb_remove_hcd+0xc7/0x240 [usbcore]
[  240.854090]  [<ffffffffa009467f>] usb_hcd_pci_remove+0x6f/0x140
[usbcore]
[  240.854091]  [<ffffffffa016c1c5>] xhci_pci_remove+0x55/0x70 [xhci_pci]

(Just one sample, there were many blocked tasks)

-Mathias


I tried the patch on top of 4.8-rc3. Reboot, suspend/resume, plug in phone and tell it to tether. Again the tether connection did not work, dhcp client doesn't get a response and times out. Then I unplug the phone and everything seems to be handled nicely. No oops or panics or hung tasks. I attach the dmesg.

Even though the patch seems to fix the trouble when unplugging, it still does nothing about the tether connection not working after a suspend/resume cycle. Do you think this is a different bug altogether? Any ideas how to trouble shoot that one?

Attachment: dmesg-Nyman-4.8rc3.log.gz
Description: application/gzip


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