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

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Message-ID: <20240310191910.GG12921@unreal>
Date: Sun, 10 Mar 2024 21:19:10 +0200
From: Leon Romanovsky <leon@...nel.org>
To: linke li <lilinke99@...com>
Cc: bmt@...ich.ibm.com, jgg@...pe.ca, linux-kernel@...r.kernel.org,
	linux-rdma@...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 08:15:25PM +0800, linke li wrote:
> I want to emphasize that if the value of orqe->flags has changed by the
> time of the second read, the value read will not satisfy the if condition,
> causing inconsistency. Given that there is already a READ_ONCE.

If value can change between subsequent reads, then you need to use locks
to make sure that it doesn't happen. Using READ_ONCE() doesn't solve the
concurrency issue, but makes sure that compiler doesn't reorder reads
and writes.

Thanks