linux-kernel - Re: [PATCH 2/2] usb: host: xhci: Handle the right timeout command

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Message-ID: <585B305E.80202@linux.intel.com>
Date:   Thu, 22 Dec 2016 09:46:06 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>,
        Mathias Nyman <mathias.nyman@...ux.intel.com>
Cc:     Baolin Wang <baolin.wang@...aro.org>,
        Mathias Nyman <mathias.nyman@...el.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        USB <linux-usb@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Mark Brown <broonie@...nel.org>,
        "Lu, Baolu" <baolu.lu@...el.com>,
        Alan Stern <stern@...land.harvard.edu>
Subject: Re: [PATCH 2/2] usb: host: xhci: Handle the right timeout command

Hi,

On 12/21/2016 11:18 PM, OGAWA Hirofumi wrote:
> Mathias Nyman <mathias.nyman@...ux.intel.com> writes:
>
>>> We set CMD_RING_STATE_ABORTED state under locking. I'm not checking what
>>> is for taking lock for register though, I guess it should be enough just
>>> lock around of read=>write of ->cmd_ring if need lock.
>> After your patch it should be enough to have the lock only while
>> reading and writing the cmd_ring register.
>>
>> If we want a locking fix that applies more easily to older stable
>> releases before your change then the lock needs to cover set
>> CMD_RING_STATE_ABORT, read cmd_reg, write cmd_reg and busiloop
>> checking CRR bit.  Otherwise the stop cmd ring interrupt handler may
>> restart the ring just before we start checing CRR. The stop cmd ring
>> interrupt will set the CMD_RING_STATE_ABORTED to
>> CMD_RING_STATE_RUNNING so ring will really restart in the interrupt
>> handler.
> Just for record (no chance to make patch I myself for now, sorry), while
> checking locking slightly, I noticed unrelated missing locking.
>
> 	xhci_cleanup_command_queue()
>
> We are calling it without locking, but we need to lock for accessing list.

Yeah. I can make the patch.

Best regards,
Lu Baolu