Received-SPF: pass (google.com: domain of linux-kernel+bounces-98211-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:4601:e00::3 as permitted sender) client-ip=2604:1380:4601:e00::3;
Message-ID: <tencent_688B20450ABBA409637C5A4BC3A7B0191D07@qq.com>
From: linke li <lilinke99@qq.com>
To: yanjun.zhu@linux.dev
Cc: bmt@zurich.ibm.com,
	jgg@ziepe.ca,
	leon@kernel.org,
	lilinke99@qq.com,
	linux-kernel@vger.kernel.org,
	linux-rdma@vger.kernel.org
Subject: Re: [PATCH] RDMA/siw: Reuse value read using READ_ONCE instead of re-reading it
Date: Sun, 10 Mar 2024 20:36:34 +0800
In-Reply-To: <2d508574-c2b8-489b-a26d-71b1c36961cf@linux.dev>
References: <2d508574-c2b8-489b-a26d-71b1c36961cf@linux.dev>
Precedence: bulk
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit

> In a complicated environment, for example, this function is called many 
> times at the same time and orqe->flags is changed at the same time, I am 
> not sure if this will introduce risks or not.

I think one function of READ_ONCE is to read a valid value while the value
may change concurrently. And there is a smp() above the READ_ONCE, which
means that the READ_ONCE is well ordered. I think it is kind of safe here.

> if you need to ensure the consistency of the flags throughout the function, not sure if the following is better or not.

> if (((orqe_flags=READ_ONCE(orqe->flags))) & SIW_WQE_VALID) {

This patch looks like exactly do the same things. The only difference I
think is the code style.

Thanks,
Linke