>From 2f8d163ba1bbcc142e7e5956cf4830e9a34e5551 Mon Sep 17 00:00:00 2001
From: Akira Yokosawa <akiyks@xxxxxxxxx>
Date: Sat, 23 Dec 2017 00:01:49 +0900
Subject: [PATCH 4/4] toolsoftrade: Add quick quiz on ACCESS_ONCE()
Put a brief history of ACCESS_ONCE() in a QQA.
Cite LWN articles on ACCESS_ONCE() and a couple of git commits in
the QQA.
Signed-off-by: Akira Yokosawa <akiyks@xxxxxxxxx>
---
toolsoftrade/toolsoftrade.tex | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
diff --git a/toolsoftrade/toolsoftrade.tex b/toolsoftrade/toolsoftrade.tex
index 855ab61..94ff444 100644
--- a/toolsoftrade/toolsoftrade.tex
+++ b/toolsoftrade/toolsoftrade.tex
@@ -1281,6 +1281,23 @@ Listing~\ref{lst:toolsoftrade:Compiler Barrier Primitive (for GCC)}.
\label{lst:toolsoftrade:Compiler Barrier Primitive (for GCC)}
\end{listing}
+\QuickQuiz{}
+ What happened to \co{ACCESS_ONCE()}?
+\QuickQuizAnswer{
+ \co{ACCESS_ONCE()} is the origin of \co{READ_ONCE()}
+ and \co{WRITE_ONCE()} in the core API of Linux kernel~\cite{
+ JonCorbet2012ACCESS:ONCE,
+ JonathanCorbet2014ACCESS:ONCEcompilerBugs}.
+ It was introduced as a helper in RCU code, but was promoted to
+ core API soon afterward~\cite{
+ PaulEMcKenney2007ACCESS:ONCE:rcu,
+ LinusTorvalds2008ACCESS:ONCE:move}. It has been finally removed
+ in favor of \co{READ_ONCE()} and \co{WRITE_ONCE()} during
+ Linux 4.15 development cycle~\cite{MarkRutland2017ACCESS:ONCE:remove}.
+ Linux kernel's \co{READ_ONCE()} and \co{WRITE_ONCE()} have
+ evolved into complex forms that look quite different.
+} \QuickQuizEnd
+
\subsection{Atomic Operations (C11)}
\label{sec:toolsoftrade:Atomic Operations (C11)}
--
2.7.4
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