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tools/memory-model: Code reorganization in lock.cat

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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>
This commit is contained in:
Alan Stern 2024-06-06 09:59:01 -04:00 committed by Paul E. McKenney
parent 4c830eef80
commit ea6ee1bac6
1 changed files with 35 additions and 21 deletions
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56
tools/memory-model/lock.cat
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@ -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)