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From: "yangx.jy@fujitsu.com" <yangx.jy@fujitsu.com>
To: Jason Gunthorpe <jgg@nvidia.com>, Tom Talpey <tom@talpey.com>
Cc: "linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>,
	"yanjun.zhu@linux.dev" <yanjun.zhu@linux.dev>,
	"rpearsonhpe@gmail.com" <rpearsonhpe@gmail.com>,
	"y-goto@fujitsu.com" <y-goto@fujitsu.com>,
	"lizhijian@fujitsu.com" <lizhijian@fujitsu.com>,
	"tomasz.gromadzki@intel.com" <tomasz.gromadzki@intel.com>
Subject: Re: [RFC PATCH 2/2] RDMA/rxe: Add RDMA Atomic Write operation
Date: Thu, 6 Jan 2022 10:52:47 +0000	[thread overview]
Message-ID: <61D6C9F9.10808@fujitsu.com> (raw)
In-Reply-To: <20220105235354.GV2328285@nvidia.com>

On 2022/1/6 7:53, Jason Gunthorpe wrote:
> On Thu, Dec 30, 2021 at 04:39:01PM -0500, Tom Talpey wrote:
>
>> Because RXE is a software provider, I believe the most natural approach
>> here is to use an atomic64_set(dst, *src).
> A smp_store_release() is most likely sufficient.
Hi Jason, Tom

Is smp_store_mb() better here? It calls WRITE_ONCE + smb_mb/barrier().
I think the semantics of 'atomic write' is to do atomic write and make 
the 8-byte data reach the memory.

Best Regards,
Xiao Yang
> The spec word 'atomic' is pretty confusing. What it is asking for, in
> the modern memory model vernacular, is 'write once' for the entire
> payload and 'release' to only be observable after other stores made by
> the same QP.
>
> 'release' semantics will depend on the CPU complex having a release
> dependency chain throughout all CPUs that completed any prior response
> on the QP. It looks like this is achieved through tasklet scheduling..
>
> Jason

  reply	other threads:[~2022-01-06 10:52 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-12-30 12:14 [RFC PATCH 0/2] RDMA/rxe: Add RDMA Atomic Write operation Xiao Yang
2021-12-30 12:14 ` [RFC PATCH 1/2] RDMA/rxe: Rename send_atomic_ack() and atomic member of struct resp_res Xiao Yang
2021-12-30 12:14 ` [RFC PATCH 2/2] RDMA/rxe: Add RDMA Atomic Write operation Xiao Yang
2021-12-30 21:39   ` Tom Talpey
2021-12-31  8:29     ` yangx.jy
2021-12-31 15:09       ` Tom Talpey
     [not found]         ` <61D563B4.2070106@fujitsu.com>
2022-01-07 15:50           ` Tom Talpey
2022-01-07 17:11             ` Jason Gunthorpe
2022-01-12  9:24             ` yangx.jy
2022-01-05 23:53     ` Jason Gunthorpe
2022-01-06 10:52       ` yangx.jy [this message]
2022-01-06 13:00         ` Jason Gunthorpe
2022-01-07  2:15           ` yangx.jy
2022-01-07 12:22             ` Jason Gunthorpe
2022-01-07 15:38               ` Tom Talpey
2022-01-07 19:28                 ` Jason Gunthorpe
2022-01-07 20:11                   ` Tom Talpey
2021-12-31  3:01   ` lizhijian
2021-12-31  6:02     ` yangx.jy
2021-12-30 19:21 ` [RFC PATCH 0/2] " Gromadzki, Tomasz
2021-12-30 21:42   ` Tom Talpey
2021-12-31  6:30     ` yangx.jy
2022-01-04  9:28       ` yangx.jy
2022-01-04 15:17         ` Tom Talpey
2022-01-05  1:00           ` yangx.jy
2022-01-06  0:01             ` Jason Gunthorpe
2022-01-06  1:54               ` yangx.jy
2022-01-10 15:42                 ` Jason Gunthorpe
2022-01-11  2:34                   ` yangx.jy
2022-01-11 23:29                     ` Jason Gunthorpe
2022-02-11 13:18           ` Gromadzki, Tomasz
2022-02-17  3:50 ` yangx.jy
2022-02-19 10:37   ` Leon Romanovsky

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