netdev - RE: [PATCH v1 1/1] Firstly, as Andy mentioned, this should be smp_rmb() instead of rmb(). considering that TSYNC is a cross-thread situation, and rmb() is a mandatory barrier which should not be used to control SMP effects, since mandatory barriers imp...

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Date:   Thu, 4 Feb 2021 08:45:41 +0000
From:   "Wanghongzhe (Hongzhe, EulerOS)" <wanghongzhe@...wei.com>
To:     Kees Cook <keescook@...omium.org>
CC:     "luto@...capital.net" <luto@...capital.net>,
        "andrii@...nel.org" <andrii@...nel.org>,
        "ast@...nel.org" <ast@...nel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "daniel@...earbox.net" <daniel@...earbox.net>,
        "john.fastabend@...il.com" <john.fastabend@...il.com>,
        "kafai@...com" <kafai@...com>,
        "kpsingh@...nel.org" <kpsingh@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "songliubraving@...com" <songliubraving@...com>,
        "wad@...omium.org" <wad@...omium.org>, "yhs@...com" <yhs@...com>
Subject: RE: [PATCH v1 1/1] Firstly, as Andy mentioned, this should be
 smp_rmb() instead of rmb(). considering that TSYNC is a cross-thread
 situation, and rmb() is a mandatory barrier which should not be used to
 control SMP effects, since mandatory barriers imp...

> Let's start with a patch that just replaces rmb() with smp_rmb() and then work
> on optimizing. Can you provide performance numbers that show
> rmb() (and soon smp_rmb()) is causing actual problems here?
Ok, I will send a patch that just replaces rmb() with smp_rmb() and give performance numbers.

> BUG() should never be used[1]. This is a recoverable situation, I think, and
> should be handled as such.

I just follow the default case behind. Let's discuss this issue in next patches. 

-- 
wanghongzhe