linux-kernel - RE: [PATCH 4/5] hv: kvp: use wrappers to propaigate state

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Message-ID: <BY2PR0301MB165435669D72713F66DC4E6EA0460@BY2PR0301MB1654.namprd03.prod.outlook.com>
Date:	Mon, 21 Sep 2015 16:31:32 +0000
From:	KY Srinivasan <kys@...rosoft.com>
To:	Olaf Hering <olaf@...fle.de>, Greg KH <gregkh@...uxfoundation.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
	"apw@...onical.com" <apw@...onical.com>,
	"vkuznets@...hat.com" <vkuznets@...hat.com>,
	"jasowang@...hat.com" <jasowang@...hat.com>
Subject: RE: [PATCH 4/5] hv: kvp: use wrappers to propaigate state



> -----Original Message-----
> From: Olaf Hering [mailto:olaf@...fle.de]
> Sent: Monday, September 21, 2015 3:18 AM
> To: KY Srinivasan <kys@...rosoft.com>; Greg KH
> <gregkh@...uxfoundation.org>
> Cc: linux-kernel@...r.kernel.org; devel@...uxdriverproject.org;
> apw@...onical.com; vkuznets@...hat.com; jasowang@...hat.com
> Subject: Re: [PATCH 4/5] hv: kvp: use wrappers to propaigate state
> 
> On Sun, Sep 20, Greg KH wrote:
> 
> > On Tue, Sep 15, 2015 at 05:37:53PM -0700, K. Y. Srinivasan wrote:
> > > @@ -122,8 +125,8 @@ static void kvp_timeout_func(struct work_struct
> *dummy)
> 
> > > +	if (kvp_get_state() > HVUTIL_READY)
> > > +		kvp_set_state(HVUTIL_READY);
> 
> > And what if the state changed the line after this?  Oops, your code is
> > hosed.  See, you need a lock, do this correctly.
> 
> KY,  can this happen?

No - the state has to be > HVUTIL_READY. Also, if the timeout fires,
it wins since other contexts will attempt to first cancel the timeout before
proceeding further.

K. Y 
> 
> Olaf