From: Mathias Nyman <mathias.nyman@linux.intel.com>
To: Greg KH <gregkh@linuxfoundation.org>
Cc: stern@rowland.harvard.edu, kishon@ti.com, hdegoede@redhat.com,
chris.chiu@canonical.com, linux-usb@vger.kernel.org,
stable@vger.kernel.org
Subject: Re: [PATCH] usb: hub: Fix usb enumeration issue due to address0 race
Date: Tue, 16 Nov 2021 10:39:18 +0200 [thread overview]
Message-ID: <dd32d4ab-dff9-0080-7911-5e1931af5c3e@linux.intel.com> (raw)
In-Reply-To: <YZNqQBd+pcXBQuAp@kroah.com>
On 16.11.2021 10.22, Greg KH wrote:
> On Tue, Nov 16, 2021 at 12:16:30AM +0200, Mathias Nyman wrote:
>> xHC hardware can only have one slot in default state with address 0
>> waiting for a unique address at a time, otherwise "undefined behavior
>> may occur" according to xhci spec 5.4.3.4
>>
>> The address0_mutex exists to prevent this across both xhci roothubs.
>>
>> If hub_port_init() fails, it may unlock the mutex and exit with a xhci
>> slot in default state. If the other xhci roothub calls hub_port_init()
>> at this point we end up with two slots in default state.
>>
>> Make sure the address0_mutex protects the slot default state across
>> hub_port_init() retries, until slot is addressed or disabled.
>>
>> Note, one known minor case is not fixed by this patch.
>> If device needs to be reset during resume, but fails all hub_port_init()
>> retries in usb_reset_and_verify_device(), then it's possible the slot is
>> still left in default state when address0_mutex is unlocked.
>>
>> Cc: <stable@vger.kernel.org>
>> Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
>
> What commit id does this "fix"?
>
Looks like original cause could be:
638139eb95d2 ("usb: hub: allow to process more usb hub events in parallel")
which was partially fixed in 4.7 by:
feb26ac31a2a ("usb: core: hub: hub_port_init lock controller instead of bus")
And now improved by this patch
-Mathias
next prev parent reply other threads:[~2021-11-16 8:37 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20211118111915eucas1p2cf4a502442e7259c6c347daf0d87259e@eucas1p2.samsung.com>
2021-11-15 22:16 ` [PATCH] usb: hub: Fix usb enumeration issue due to address0 race Mathias Nyman
2021-11-16 8:22 ` Greg KH
2021-11-16 8:39 ` Mathias Nyman [this message]
2021-11-18 11:19 ` Marek Szyprowski
2021-11-18 13:50 ` Mathias Nyman
2021-11-22 10:44 ` Mathias Nyman
2021-11-22 10:50 ` [RFT PATCH] usb: hub: Fix locking issues with address0_mutex Mathias Nyman
2021-11-22 12:27 ` Marek Szyprowski
2021-11-23 9:18 ` Mathias Nyman
2021-11-22 15:41 ` Hans de Goede
2021-11-23 9:31 ` Mathias Nyman
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