Re: [dpdk-dev] [PATCH v4 0/4] fix race condition in enqueue/dequeue because of cpu reorder

[Jerin Jacob <jerin.jacob@caviumnetworks.com>]

-----Original Message-----
> Date: Wed, 8 Nov 2017 23:11:32 +0800
> From: Jia He <hejianet@gmail.com>
> To: Bruce Richardson <bruce.richardson@intel.com>
> Cc: jerin.jacob@caviumnetworks.com, dev@dpdk.org, olivier.matz@6wind.com,
>  konstantin.ananyev@intel.com, jianbo.liu@arm.com, hemant.agrawal@nxp.com
> Subject: Re: [PATCH v4 0/4] fix race condition in enqueue/dequeue because
>  of cpu reorder
> User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101
>  Thunderbird/52.4.0
> 
> Hi Bruce
> 
> 
> On 11/8/2017 8:15 PM, Bruce Richardson Wrote:
> > On Wed, Nov 08, 2017 at 09:54:37AM +0000, Jia He wrote:
> > > We watched a rte panic of mbuf_autotest in our qualcomm arm64 server
> > > due to a possible race condition.
> > > 
> > > To fix this race, there are 2 options as suggested by Jerin: 1. use
> > > rte_smp_rmb 2. use load_acquire/store_release(refer to [2]).
> > > CONFIG_RTE_RING_USE_C11_MEM_MODEL is provided, and by default it is
> > > "y" only on arm64 so far.
> > > 
> > > The reason why providing 2 options is due to the performance benchmark
> > > difference in different arm machines.
> > > 
> > > Already fuctionally tested on the machines as follows: - on X86 - on
> > > arm64 with CONFIG_RTE_RING_USE_C11_MEM_MODEL=y - on arm64 with
> > > CONFIG_RTE_RING_USE_C11_MEM_MODEL=n
> > > 
> > > --- Changelog: V4: split into small patches V3: arch specific
> > > implementation for enqueue/dequeue barrier V2: let users choose
> > > whether using load_acquire/store_release V1: rte_smp_rmb() between 2
> > > loads
> > > 
> > > Jia He (4): eal/arm64: remove the braces {} for dmb() and dsb() ring:
> > > guarantee load/load order in enqueue and dequeue ring: introduce new
> > > header file to include common functions ring: introduce new header
> > > file to support C11 memory model
> > > 
> > I'm wondering what the merge plans are for this set, given we are now
> > past RC3 in 17.11? As the rings are broken on ARM machines we need to
> > merge in some fix, but I'm a little concerned about the scope of the
> > changes from the 3rd and 4th patches. Would it be acceptable to just
> > merge in patches 1 & 2 in 17.11 and leave the rework and C11 memory
> > model additions in patches 3 & 4 to 18.02 release?
> As far as I'm concerned, it is ok.

It is OK to me as well. May be Jia can send 0-1 and 2-3 as separate
series with exiting comments.


> 
> Cheers,
> Jia
>