[dpdk-dev] [PATCH v1 5/5] ixgbe: Add LRO support

[Avi Kivity]

On 03/04/2015 02:33 AM, Stephen Hemminger wrote:
> On Tue,  3 Mar 2015 21:48:43 +0200
> Vlad Zolotarov <vladz at cloudius-systems.com> wrote:
>
>> +		 * TODO:
>> +		 *    - Get rid of "volatile" crap and let the compiler do its
>> +		 *      job.
>> +		 *    - Use the proper memory barrier (rte_rmb()) to ensure the
>> +		 *      memory ordering below.
> This comment screams "this is broken".
> Why not get proper architecture independent barriers in DPDK first.

C11 has arch independent memory barriers, so this can be as simple as 
-std=gnu11 (default in gcc 5, anyway).

Not only do we get the barriers for free, but they are also properly 
integrated with the compiler, so for example a release barrier won't 
stop the compiler from hoisting a later accesses to before the store, or 
cause spurious reloads, due to the memory clobber.