linux-kernel - Re: [RFC v2 2/2] docs: ftrace: Fix typos

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Message-ID: <20191125123709.5eff70a9@gandalf.local.home>
Date:   Mon, 25 Nov 2019 12:37:09 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     "Frank A. Cancio Bello" <frank@...eralsoftwareinc.com>
Cc:     Ingo Molnar <mingo@...hat.com>, Jonathan Corbet <corbet@....net>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        joel@...lfernandes.org, saiprakash.ranjan@...eaurora.org
Subject: Re: [RFC v2 2/2] docs: ftrace: Fix typos

On Sun, 24 Nov 2019 23:38:41 -0500
"Frank A. Cancio Bello" <frank@...eralsoftwareinc.com> wrote:

> --- a/Documentation/trace/ring-buffer-design.txt
> +++ b/Documentation/trace/ring-buffer-design.txt
> @@ -37,7 +37,7 @@ commit_page - a pointer to the page with the last finished non-nested write.
>  
>  cmpxchg - hardware-assisted atomic transaction that performs the following:
>  
> -   A = B iff previous A == C
> +   A = B if previous A == C

This wasn't a typo. "iff" means "if and only if" which is a standard
notation. That is, this is shorthand for:

  A = B if previous A == C
  previous A == C if A = B

-- Steve


>  
>     R = cmpxchg(A, C, B) is saying that we replace A with B if and only if
>        current A is equal to C, and we put the old (current) A into R
> --