future/tm: TM-unfriendly operations and composability

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

1 files changed, 10 insertions, 0 deletions

diff --git a/future/tm.tex b/future/tm.tex
index e41ed685..b649f3cc 100644
--- a/future/tm.tex
+++ b/future/tm.tex
@@ -81,6 +81,16 @@ This section therefore critiques transactional memory's outside-world
 capabilities, focusing on I/O operations, time delays, and persistent
 storage.
 
+And these interactions with the outside world are the rock upon which
+the claims of unconditional TM composability are shattered.
+Yes, you can compose transactions, but only as long as there are no
+intervening TM-unfriendly operations.
+Just as you can compose lock-based critical sections, but only as long
+as doing so does not introduce deadlocks.
+
+In the end, it is unclear whether TM really provides better composability
+than does locking in real-world code.
+
 \subsubsection{I/O Operations}
 \label{sec:future:I/O Operations}