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authorAlan Stern <stern@rowland.harvard.edu>2024-06-06 15:59:01 +0200
committerPaul E. McKenney <paulmck@kernel.org>2024-06-06 20:24:58 +0200
commitea6ee1bac6034cb4e91bcc229ed1354ca1a024d5 (patch)
tree2becc764127af9315b63812cd688c64a290bebf3
parenttools/memory-model: Fix bug in lock.cat (diff)
downloadlinux-ea6ee1bac6034cb4e91bcc229ed1354ca1a024d5.tar.xz
linux-ea6ee1bac6034cb4e91bcc229ed1354ca1a024d5.zip
tools/memory-model: Code reorganization in lock.cat
Code reorganization for the lock.cat file in tools/memory-model: Improve the efficiency by ruling out right at the start RU events (spin_is_locked() calls that return False) inside a critical section for the same lock. Improve the organization of the code for handling LF and RU events by pulling the definitions of the pair-to-relation macro out from two different complicated compound expressions, using a single standalone definition instead. Rewrite the calculations of the rf relation for LF and RU events, for greater clarity. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Tested-by: Andrea Parri <parri.andrea@gmail.com> Acked-by: Andrea Parri <parri.andrea@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
-rw-r--r--tools/memory-model/lock.cat56
1 files changed, 35 insertions, 21 deletions
diff --git a/tools/memory-model/lock.cat b/tools/memory-model/lock.cat
index 21ba65086938..03c12efed66a 100644
--- a/tools/memory-model/lock.cat
+++ b/tools/memory-model/lock.cat
@@ -54,6 +54,12 @@ flag ~empty LKR \ domain(lk-rmw) as unpaired-LKR
*)
empty ([LKW] ; po-loc ; [LKR]) \ (po-loc ; [UL] ; po-loc) as lock-nest
+(*
+ * In the same way, spin_is_locked() inside a critical section must always
+ * return True (no RU events can be in a critical section for the same lock).
+ *)
+empty ([LKW] ; po-loc ; [RU]) \ (po-loc ; [UL] ; po-loc) as nested-is-locked
+
(* The final value of a spinlock should not be tested *)
flag ~empty [FW] ; loc ; [ALL-LOCKS] as lock-final
@@ -79,39 +85,47 @@ empty ([UNMATCHED-LKW] ; loc ; [UNMATCHED-LKW]) \ id as unmatched-locks
(* rfi for LF events: link each LKW to the LF events in its critical section *)
let rfi-lf = ([LKW] ; po-loc ; [LF]) \ ([LKW] ; po-loc ; [UL] ; po-loc)
-(* rfe for LF events *)
+(* Utility macro to convert a single pair to a single-edge relation *)
+let pair-to-relation p = p ++ 0
+
+(*
+ * If a given LF event e is outside a critical section, it cannot read
+ * internally but it may read from an LKW event in another thread.
+ * Compute the relation containing these possible edges.
+ *)
+let possible-rfe-noncrit-lf e = (LKW * {e}) & loc & ext
+
+(* Compute set of sets of possible rfe edges for LF events *)
let all-possible-rfe-lf =
(*
- * Given an LF event r, compute the possible rfe edges for that event
- * (all those starting from LKW events in other threads),
- * and then convert that relation to a set of single-edge relations.
+ * Convert the possible-rfe-noncrit-lf relation for e
+ * to a set of single edges
*)
- let possible-rfe-lf r =
- let pair-to-relation p = p ++ 0
- in map pair-to-relation ((LKW * {r}) & loc & ext)
- (* Do this for each LF event r that isn't in rfi-lf *)
- in map possible-rfe-lf (LF \ range(rfi-lf))
+ let set-of-singleton-rfe-lf e =
+ map pair-to-relation (possible-rfe-noncrit-lf e)
+ (* Do this for each LF event e that isn't in rfi-lf *)
+ in map set-of-singleton-rfe-lf (LF \ range(rfi-lf))
(* Generate all rf relations for LF events *)
with rfe-lf from cross(all-possible-rfe-lf)
let rf-lf = rfe-lf | rfi-lf
(*
- * RU, i.e., spin_is_locked() returning False, is slightly different.
- * We rely on the memory model to rule out cases where spin_is_locked()
- * within one of the lock's critical sections returns False.
+ * A given RU event e may read internally from the last po-previous UL,
+ * or it may read from a UL event in another thread or the initial write.
+ * Compute the relation containing these possible edges.
*)
+let possible-rf-ru e = (((UL * {e}) & po-loc) \
+ ([UL] ; po-loc ; [UL] ; po-loc)) |
+ (((UL | IW) * {e}) & loc & ext)
-(*
- * rf for RU events: an RU may read from an external UL or the initial write,
- * or from the last po-previous UL
- *)
+(* Compute set of sets of possible rf edges for RU events *)
let all-possible-rf-ru =
- let possible-rf-ru r =
- let pair-to-relation p = p ++ 0
- in map pair-to-relation ((((UL | IW) * {r}) & loc & ext) |
- (((UL * {r}) & po-loc) \ ([UL] ; po-loc ; [LKW] ; po-loc)))
- in map possible-rf-ru RU
+ (* Convert the possible-rf-ru relation for e to a set of single edges *)
+ let set-of-singleton-rf-ru e =
+ map pair-to-relation (possible-rf-ru e)
+ (* Do this for each RU event e *)
+ in map set-of-singleton-rf-ru RU
(* Generate all rf relations for RU events *)
with rf-ru from cross(all-possible-rf-ru)