tools/memory-model: Remove out-of-date SRCU documentation
authorAndrea Parri <parri.andrea@gmail.com>
Thu, 23 Mar 2023 01:37:51 +0000 (02:37 +0100)
committerPaul E. McKenney <paulmck@kernel.org>
Fri, 24 Mar 2023 17:24:48 +0000 (10:24 -0700)
Commit 6cd244c87428 ("tools/memory-model: Provide exact SRCU semantics")
changed the semantics of partially overlapping SRCU read-side critical
sections (among other things), making such documentation out-of-date.
The new, semantic changes are discussed in explanation.txt.  Remove the
out-of-date documentation.

Signed-off-by: Andrea Parri <parri.andrea@gmail.com>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
tools/memory-model/Documentation/litmus-tests.txt

index 26554b1..acac527 100644 (file)
@@ -1028,32 +1028,7 @@ Limitations of the Linux-kernel memory model (LKMM) include:
                additional call_rcu() process to the site of the
                emulated rcu-barrier().
 
-       e.      Although sleepable RCU (SRCU) is now modeled, there
-               are some subtle differences between its semantics and
-               those in the Linux kernel.  For example, the kernel
-               might interpret the following sequence as two partially
-               overlapping SRCU read-side critical sections:
-
-                        1  r1 = srcu_read_lock(&my_srcu);
-                        2  do_something_1();
-                        3  r2 = srcu_read_lock(&my_srcu);
-                        4  do_something_2();
-                        5  srcu_read_unlock(&my_srcu, r1);
-                        6  do_something_3();
-                        7  srcu_read_unlock(&my_srcu, r2);
-
-               In contrast, LKMM will interpret this as a nested pair of
-               SRCU read-side critical sections, with the outer critical
-               section spanning lines 1-7 and the inner critical section
-               spanning lines 3-5.
-
-               This difference would be more of a concern had anyone
-               identified a reasonable use case for partially overlapping
-               SRCU read-side critical sections.  For more information
-               on the trickiness of such overlapping, please see:
-               https://paulmck.livejournal.com/40593.html
-
-       f.      Reader-writer locking is not modeled.  It can be
+       e.      Reader-writer locking is not modeled.  It can be
                emulated in litmus tests using atomic read-modify-write
                operations.