linux-kernel - Re: [PATCH] RDMA/siw: Reuse value read using READ

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Message-ID: <CAEz=Lcvm9a0Zg-V8O5xPZ0t3BHNj8+H-wSdSn0i4eZfZgsqRNw@mail.gmail.com>
Date: Mon, 11 Mar 2024 01:02:18 +0800
From: Greg Sword <gregsword0@...il.com>
To: Leon Romanovsky <leon@...nel.org>
Cc: linke li <lilinke99@...com>, Bernard Metzler <bmt@...ich.ibm.com>, Jason Gunthorpe <jgg@...pe.ca>, 
	linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] RDMA/siw: Reuse value read using READ_ONCE instead of
 re-reading it

On Sun, Mar 10, 2024 at 7:33 PM Leon Romanovsky <leon@...nel.org> wrote:
>
> On Sat, Mar 09, 2024 at 08:27:16PM +0800, linke li wrote:
> > In siw_orqe_start_rx, the orqe's flag in the if condition is read using
> > READ_ONCE, checked, and then re-read, voiding all guarantees of the
> > checks. Reuse the value that was read by READ_ONCE to ensure the
> > consistency of the flags throughout the function.
>
> Please read include/asm-generic/rwonce.h comments when READ_ONCE() is used.
> There is no value in caching the output of READ_ONCE().

Agree. Read the link
https://www.kernel.org/doc/Documentation/memory-barriers.txt, too

>
> Thanks
>