[PATCH 3/9] Drivers: hv: utils: introduce HVUTIL_TRANSPORT_DESTROY mode

[Vitaly Kuznetsov]

Dexuan Cui <decui at microsoft.com> writes:

>> -----Original Message-----
>> From: devel [mailto:driverdev-devel-bounces at linuxdriverproject.org] On Behalf
>> Of K. Y. Srinivasan
>> Sent: Tuesday, December 15, 2015 11:02
>> To: gregkh at linuxfoundation.org; linux-kernel at vger.kernel.org;
>> devel at linuxdriverproject.org; olaf at aepfle.de; apw at canonical.com;
>> vkuznets at redhat.com; jasowang at redhat.com
>> Subject: [PATCH 3/9] Drivers: hv: utils: introduce HVUTIL_TRANSPORT_DESTROY
>> mode
>> 
>> From: Vitaly Kuznetsov <vkuznets at 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?

Oh, sorry, my bad -- hvt_op_poll() returns unsigned int and -EBADF is
definitely inappropriate. I see this patch was already merged to
char-misc-testing so I'll send a follow-up patch to fix things up.

Thanks!

-- 
  Vitaly