From: Mathias Nyman <mathias.nyman@linux.intel.com>
To: Chris Bainbridge <chris.bainbridge@gmail.com>,
Alan Stern <stern@rowland.harvard.edu>
Cc: johan@kernel.org, linux-usb@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] usb: host: xhci: Replace bus lock with host controller lock
Date: Wed, 10 Feb 2016 18:50:06 +0200 [thread overview]
Message-ID: <56BB6A3E.4020006@linux.intel.com> (raw)
In-Reply-To: <20160205151407.GA5257@localhost>
On 05.02.2016 17:14, Chris Bainbridge wrote:
> Running task list at fail point:
...
> Some of the functions appear to be inlined, the exact call chain is:
>
> hub_port_init
> usb_get_device_descriptor
> usb_get_descriptor
> usb_control_msg
> usb_internal_control_msg
> usb_start_wait_urb
> usb_submit_urb / wait_for_completion_timeout / usb_kill_urb
>
> hub_port_init
> hub_set_address
> xhci_address_device
> xhci_setup_device
>
hub_port_reset() will end up moving the corresponding xhci device slot to default state.
As hub_port_reset() is called several times in hub_port_init() It sounds reasonable
that we could end up with two threads having their xhci device slots in default state at
the same time, which according to xhci 4.5.3 specs still is a big no no.
So both threads fail at their next task after this.
One fails to read the descriptor, and the other fails addressing the device.
Nice catch btw.
> So xhci_setup_device is entered while there is an outstanding URB on the
> other bus. Unless anyone can think of a better way to fix this I'll make
> the requested changes and resend my patch.
>
For what it's wort I think that this suggested controller mutex sounds like a good idea.
Should work for xhci at least.
-Mathias
prev parent reply other threads:[~2016-02-10 16:44 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-04 19:46 [PATCH] usb: host: xhci: Replace bus lock with host controller lock Chris Bainbridge
2016-02-04 21:00 ` Alan Stern
2016-02-04 22:06 ` Chris Bainbridge
2016-02-05 2:45 ` Alan Stern
2016-02-05 15:14 ` Chris Bainbridge
2016-02-10 16:50 ` Mathias Nyman [this message]
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