linux-kernel - Re: [PATCH] documentation: Fix two-CPU control-dependency example

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Message-ID: <20170721002440.m6e5sdsa53lxygo4@tardis>
Date:   Fri, 21 Jul 2017 08:24:40 +0800
From:   Boqun Feng <boqun.feng@...il.com>
To:     "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:     Akira Yokosawa <akiyks@...il.com>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] documentation: Fix two-CPU control-dependency example

On Thu, Jul 20, 2017 at 04:07:14PM -0700, Paul E. McKenney wrote:
[...]
> > 
> > So if I respin the patch with the extern, would you still feel reluctant?
> 
> Yes, because I am not seeing how this change helps.  What is this telling
> the reader that the original did not, and how does it help the reader
> generate good concurrent code?
> 

One thing I think we probably should do is to make READ_ONCE() semantics
more clear, i.e. call it out that in our conceptual model for kernel
programming we always rely on the compiler to be serious about the
return value of READ_ONCE(). I didn't find the comment before
READ_ONCE() or memory-barriers.txt talking about something similar.

Or am I the only one having this kinda semantics guarantee in mind?

Regards,
Boqun

> 							Thanx, Paul
>