linux-kernel - RE: [PATCH 1/3] Drivers: hv: utils: fix hvt_op_poll() return value on transport destroy

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Date:	Wed, 16 Dec 2015 10:41:24 +0000
From:	Dexuan Cui <decui@...rosoft.com>
To:	Vitaly Kuznetsov <vkuznets@...hat.com>
CC:	KY Srinivasan <kys@...rosoft.com>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
	"olaf@...fle.de" <olaf@...fle.de>,
	"apw@...onical.com" <apw@...onical.com>,
	"jasowang@...hat.com" <jasowang@...hat.com>
Subject: RE: [PATCH 1/3] Drivers: hv: utils: fix hvt_op_poll() return value on
 transport destroy

> From: Vitaly Kuznetsov [mailto:vkuznets@...hat.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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