linux-kernel - Re: [PATCH V3 1/1] Drivers: hv: vmbus: Fix a bug in vmbus_establish

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Message-ID: <20141215185104.GA25345@hudson.localdomain>
Date:	Mon, 15 Dec 2014 10:51:04 -0800
From:	Jeremiah Mahler <jmmahler@...il.com>
To:	Andy Whitcroft <apw@...onical.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>,
	"jasowang@...hat.com" <jasowang@...hat.com>,
	"mcb30@...e.org" <mcb30@...e.org>
Subject: Re: [PATCH V3 1/1] Drivers: hv: vmbus: Fix a bug in
 vmbus_establish_gpadl()

Andy,

On Mon, Dec 15, 2014 at 03:47:04PM +0000, Andy Whitcroft wrote:
> On Sun, Dec 14, 2014 at 11:59:19PM -0800, Jeremiah Mahler wrote:
[...]
> 
> The calculation appears identical to my reading, the original form was:
> 
>   next_gpadl_handle = atomic_read(&vmbus_connection.next_gpadl_handle);
>   atomic_inc(&vmbus_connection.next_gpadl_handle);
> 
> or:
> 
>   y = x;
>   x++;
> 
> so y == x' (x before incrementing)
> 
> the new code is:
> 
>   next_gpadl_handle = (atomic_inc_return(&vmbus_connection.next_gpadl_handle) - 1);
> 
> or:
> 
>   y = ++x - 1;
> 
> Also making y = x' (x before incrementing)
> 
> -apw

Ah, you are right.  The increment before/after messed me up.

Thanks for clearing that up for me :-)

-- 
- Jeremiah Mahler
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