From: Dexuan Cui <decui@microsoft.com>
To: KY Srinivasan <kys@microsoft.com>,
        "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "devel@linuxdriverproject.org" <devel@linuxdriverproject.org>,
        "olaf@aepfle.de" <olaf@aepfle.de>,
        "apw@canonical.com" <apw@canonical.com>,
        "vkuznets@redhat.com" <vkuznets@redhat.com>,
        "jasowang@redhat.com" <jasowang@redhat.com>
Subject: RE: [PATCH 3/9] Drivers: hv: utils: introduce
 HVUTIL_TRANSPORT_DESTROY mode
Thread-Topic: [PATCH 3/9] Drivers: hv: utils: introduce
 HVUTIL_TRANSPORT_DESTROY mode
Thread-Index: AQHRNtfwg9Adofxc6kOerKSbJPrJ4J7L9OBg
Date: Tue, 15 Dec 2015 12:14:53 +0000
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> -----Original Message-----
> From: devel [mailto:driverdev-devel-bounces@linuxdriverproject.org] On Behalf
> Of K. Y. Srinivasan
> Sent: Tuesday, December 15, 2015 11:02
> To: gregkh@linuxfoundation.org; linux-kernel@vger.kernel.org;
> devel@linuxdriverproject.org; olaf@aepfle.de; apw@canonical.com;
> vkuznets@redhat.com; jasowang@redhat.com
> Subject: [PATCH 3/9] Drivers: hv: utils: introduce HVUTIL_TRANSPORT_DESTROY
> mode
> 
> From: Vitaly Kuznetsov <vkuznets@redhat.com>
> 
> When Hyper-V host asks us to remove some util driver by closing the
> appropriate channel there is no easy way to force the current file
> descriptor holder to hang up but we can start to respond -EBADF to all
> operations asking it to exit gracefully.
> 
> As we're setting hvt->mode from two separate contexts now we need to use
> a proper locking.
> 
> ...
> @@ -99,6 +107,10 @@ static unsigned int hvt_op_poll(struct file *file,
> poll_table *wait)
>  	hvt = container_of(file->f_op, struct hvutil_transport, fops);
> 
>  	poll_wait(file, &hvt->outmsg_q, wait);
> +
> +	if (hvt->mode == HVUTIL_TRANSPORT_DESTROY)
> +		return -EBADF;
> +
>  	if (hvt->outmsg_len > 0)
>  		return POLLIN | POLLRDNORM;

Hi Vitaly, 
Should hvt_op_poll() return -EBADF -- I think it probably
should return POLLERR or POLLHUP?

-- Dexuan
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