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Subject[PATCH RFC LKMM 7/7] tools/memory-model: Dynamically check SRCU lock-to-unlock matching
Date
From: Luc Maranget <Luc.Maranget@inria.fr>

This commit checks that the return value of srcu_read_lock() is passed
to the matching srcu_read_unlock(), where "matching" is determined by
nesting. This check operates as follows:

1. srcu_read_lock() creates an integer token, which is stored into
the generated events.
2. srcu_read_unlock() records its second (token) argument into the
generated event.
3. A new herd primitive 'different-values' filters out pairs of events
with identical values from the relation passed as its argument.
4. The bell file applies the above primitive to the (srcu)
read-side-critical-section relation 'srcu-rscs' and flags non-empty
results.

BEWARE: Works only with herd version 7.51+6 and onwards.

Signed-off-by: Luc Maranget <Luc.Maranget@inria.fr>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
[ paulmck: Apply Andrea Parri's off-list feedback. ]
---
tools/memory-model/linux-kernel.bell | 3 +++
tools/memory-model/linux-kernel.cat | 2 ++
tools/memory-model/linux-kernel.def | 2 +-
3 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/tools/memory-model/linux-kernel.bell b/tools/memory-model/linux-kernel.bell
index 9c42cd9ddcb4..def9131d3d8e 100644
--- a/tools/memory-model/linux-kernel.bell
+++ b/tools/memory-model/linux-kernel.bell
@@ -73,3 +73,6 @@ flag ~empty Srcu-unlock \ range(srcu-rscs) as unbalanced-srcu-locking

(* Check for use of synchronize_srcu() inside an RCU critical section *)
flag ~empty rcu-rscs & (po ; [Sync-srcu] ; po) as invalid-sleep
+
+(* Validate SRCU dynamic match *)
+flag ~empty different-values(srcu-rscs) as srcu-bad-nesting
diff --git a/tools/memory-model/linux-kernel.cat b/tools/memory-model/linux-kernel.cat
index 8dcb37835b61..95bf45f1215f 100644
--- a/tools/memory-model/linux-kernel.cat
+++ b/tools/memory-model/linux-kernel.cat
@@ -1,5 +1,7 @@
// SPDX-License-Identifier: GPL-2.0+
(*
+ * Requires herd version 7.51+6 or higher.
+ *
* Copyright (C) 2015 Jade Alglave <j.alglave@ucl.ac.uk>,
* Copyright (C) 2016 Luc Maranget <luc.maranget@inria.fr> for Inria
* Copyright (C) 2017 Alan Stern <stern@rowland.harvard.edu>,
diff --git a/tools/memory-model/linux-kernel.def b/tools/memory-model/linux-kernel.def
index 1d6a120cde14..0c3f0ef486f4 100644
--- a/tools/memory-model/linux-kernel.def
+++ b/tools/memory-model/linux-kernel.def
@@ -49,7 +49,7 @@ synchronize_rcu_expedited() { __fence{sync-rcu}; }

// SRCU
srcu_read_lock(X) __srcu{srcu-lock}(X)
-srcu_read_unlock(X,Y) { __srcu{srcu-unlock}(X); }
+srcu_read_unlock(X,Y) { __srcu{srcu-unlock}(X,Y); }
synchronize_srcu(X) { __srcu{sync-srcu}(X); }

// Atomic
--
2.17.1
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