From: Jason Gunthorpe <jgg@nvidia.com>
To: "yangx.jy@fujitsu.com" <yangx.jy@fujitsu.com>
Cc: Tom Talpey <tom@talpey.com>,
"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 09:00:38 -0400 [thread overview]
Message-ID: <20220106130038.GB2328285@nvidia.com> (raw)
In-Reply-To: <61D6C9F9.10808@fujitsu.com>
On Thu, Jan 06, 2022 at 10:52:47AM +0000, yangx.jy@fujitsu.com wrote:
> 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.
No, it is not 'data reach memory' it is a 'release' in that if the CPU
later does an 'acquire' on the written data it is guarenteed to see
all the preceeding writes.
Memory barriers are always paired with read and write, it is important
to understand what the read half of the pair is.
Jason
next prev parent reply other threads:[~2022-01-06 13:00 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
2022-01-06 13:00 ` Jason Gunthorpe [this message]
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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