From: Dexuan Cui <decui@microsoft.com>
To: Vitaly Kuznetsov <vkuznets@redhat.com>
CC: 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>,
        "jasowang@redhat.com" <jasowang@redhat.com>
Subject: RE: [PATCH 1/3] Drivers: hv: utils: fix hvt_op_poll() return value on
 transport destroy
Thread-Topic: [PATCH 1/3] Drivers: hv: utils: fix hvt_op_poll() return value
 on transport destroy
Thread-Index: AQHRN4t+8Wae3oS70U2Wyk1sqKQcc57NKK7ggAA+psqAAARG0A==
Date: Wed, 16 Dec 2015 10:41:24 +0000
Message-ID: <3c8623a7ab554bf4b426b8eedd9e2c21@HKXPR3004MB0088.064d.mgd.msft.net>
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 <877fkevgq3.fsf@vitty.brq.redhat.com>
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> From: Vitaly Kuznetsov [mailto:vkuznets@redhat.com]
> ...
> >> @@ -109,7 +109,7 @@ static unsigned int hvt_op_poll(struct file *file,
> >> poll_table *wait)
> >>  	poll_wait(file, &hvt->outmsg_q, wait);
> >>
> >>  	if (hvt->mode == HVUTIL_TRANSPORT_DESTROY)
> >> -		return -EBADF;
> >> +		return POLLERR | POLLHUP;
> >>
> >>  	if (hvt->outmsg_len > 0)
> >>  		return POLLIN | POLLRDNORM;
> >> --
> >
> > Hi Vitaly,
> > The daemon only polls on POLLIN.
> > I'm not sure returning "POLLERR | POLLHUP" here can wake up the daemon or
> not.
> >
> 
> I tested this patch with hv_kvp_daemon which does poll() and it
> works: we wake up all pollers from hvutil_transport_destroy(). Here
> we just need to return proper value. Actually, the return value doesn't
> really matter -- we do read() after poll() and get -EBADF there. But
> let's be consistent.
> 
>   Vitaly

Thanks Vitaly for the explanation!

I checked do_pollfd() and can confirm it's OK.

Thanks,
-- Dexuan
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