linux-kernel - Re: [PATCH net] rds: Make sure updates to cp_send

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Date:   Thu, 20 Jul 2017 15:33:19 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     Haakon.Bugge@...cle.com
Cc:     santosh.shilimkar@...cle.com, netdev@...r.kernel.org,
        linux-rdma@...r.kernel.org, rds-devel@....oracle.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net] rds: Make sure updates to cp_send_gen can be
 observed

From: Håkon Bugge <Haakon.Bugge@...cle.com>
Date: Thu, 20 Jul 2017 12:28:55 +0200

> cp->cp_send_gen is treated as a normal variable, although it may be
> used by different threads.
> 
> This is fixed by using {READ,WRITE}_ONCE when it is incremented and
> READ_ONCE when it is read outside the {acquire,release}_in_xmit
> protection.
> 
> Normative reference from the Linux-Kernel Memory Model:
> 
>     Loads from and stores to shared (but non-atomic) variables should
>     be protected with the READ_ONCE(), WRITE_ONCE(), and
>     ACCESS_ONCE().
> 
> Clause 5.1.2.4/25 in the C standard is also relevant.
> 
> Signed-off-by: Håkon Bugge <haakon.bugge@...cle.com>
> Reviewed-by: Knut Omang <knut.omang@...cle.com>

Applied, thanks.