Re: [PATCH memory-model 7/8] tools/memory-model: Add documentation about SRCU read-side critical sections

[Andrea Parri <parri.andrea@gmail.com>]

On Mon, Mar 20, 2023 at 06:02:45PM -0700, Paul E. McKenney wrote:
> From: Alan Stern <stern@rowland.harvard.edu>
> 
> Expand the discussion of SRCU and its read-side critical sections in
> the Linux Kernel Memory Model documentation file explanation.txt.  The
> new material discusses recent changes to the memory model made in
> commit 6cd244c87428 ("tools/memory-model: Provide exact SRCU
> semantics").

How about squashing the diff below (adjusting subject and changelog):

  Andrea

diff --git a/tools/memory-model/Documentation/litmus-tests.txt b/tools/memory-model/Documentation/litmus-tests.txt
index 26554b1c5575e..acac527328a1f 100644
--- a/tools/memory-model/Documentation/litmus-tests.txt
+++ b/tools/memory-model/Documentation/litmus-tests.txt
@@ -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.
 

  Andrea