memorder: Add QQ about non-load loads for address dependencies

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

1 files changed, 19 insertions, 0 deletions

diff --git a/memorder/memorder.tex b/memorder/memorder.tex
index 3d2881df..1c882ea4 100644
--- a/memorder/memorder.tex
+++ b/memorder/memorder.tex
@@ -1822,6 +1822,25 @@ This means that the exact same sequence of instructions used to traverse
 a linked data structure in single-threaded code provides weak but extremely
 useful ordering in concurrent code.
 
+\QuickQuiz{
+	Must an address dependency begin with a load instruction?
+	Why not something like \co{xchg_relaxed()}, which also loads
+	a value from memory?
+}\QuickQuizAnswer{
+	Yes, pretty much any instruction that loads a value from memory
+	can start an address dependency, including certain atomic operations
+	such as \co{xchg_relaxed()}.
+	The same is true of the control and data dependencies discussed in
+	\cref{sec:memorder:Control Dependencies,sec:memorder:Data Dependencies}.
+
+	However, in all three cases, it is often the case that if you
+	are going to start your dependency with an atomic operation,
+	it will be more convenient and maintainable to instead use
+	an atomic operation with acquire semantics, in this example,
+	\co{xchg_acquire()} or maybe even just the fully ordered
+	\co{xchg()}.
+}\QuickQuizEnd
+
 \begin{listing}
 \input{CodeSamples/formal/litmus/C-MP+o-wmb-o+o-addr-o@whole.fcv}
 \caption{Message-Passing Address-Dependency Litmus Test (No Ordering Before v4.15)}