tools/memory-model/lock.cat

// SPDX-License-Identifier: GPL-2.0+
(*
 * Copyright (C) 2016 Luc Maranget <luc.maranget@inria.fr> for Inria
 * Copyright (C) 2017 Alan Stern <stern@rowland.harvard.edu>
 *)

(*
 * Generate coherence orders and handle lock operations
 *)

include "cross.cat"

(*
 * The lock-related events generated by herd7 are as follows:
 *
 * LKR		Lock-Read: the read part of a spin_lock() or successful
 *			spin_trylock() read-modify-write event pair
 * LKW		Lock-Write: the write part of a spin_lock() or successful
 *			spin_trylock() RMW event pair
 * UL		Unlock: a spin_unlock() event
 * LF		Lock-Fail: a failed spin_trylock() event
 * RL		Read-Locked: a spin_is_locked() event which returns True
 * RU		Read-Unlocked: a spin_is_locked() event which returns False
 *
 * LKR and LKW events always come paired, like all RMW event sequences.
 *
 * LKR, LF, RL, and RU are read events; LKR has Acquire ordering.
 * LKW and UL are write events; UL has Release ordering.
 * LKW, LF, RL, and RU have no ordering properties.
 *)

(* Backward compatibility *)
let RL = try RL with emptyset
let RU = try RU with emptyset

(* Treat RL as a kind of LF: a read with no ordering properties *)
let LF = LF | RL

(* There should be no ordinary R or W accesses to spinlocks or SRCU structs *)
let ALL-LOCKS = LKR | LKW | UL | LF | RU | Srcu-lock | Srcu-unlock | Sync-srcu
flag ~empty [M \ IW \ ALL-LOCKS] ; loc ; [ALL-LOCKS] as mixed-lock-accesses

(* Link Lock-Reads to their RMW-partner Lock-Writes *)
let lk-rmw = ([LKR] ; po-loc ; [LKW]) \ (po ; po)
let rmw = rmw | lk-rmw

(* The litmus test is invalid if an LKR/LKW event is not part of an RMW pair *)
flag ~empty LKW \ range(lk-rmw) as unpaired-LKW
flag ~empty LKR \ domain(lk-rmw) as unpaired-LKR

(*
 * An LKR must always see an unlocked value; spin_lock() calls nested
 * inside a critical section (for the same lock) always deadlock.
 *)
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

(*
 * Put lock operations in their appropriate classes, but leave UL out of W
 * until after the co relation has been generated.
 *)
let R = R | LKR | LF | RU
let W = W | LKW

let Release = Release | UL
let Acquire = Acquire | LKR

(* Match LKW events to their corresponding UL events *)
let critical = ([LKW] ; po-loc ; [UL]) \ (po-loc ; [LKW | UL] ; po-loc)

flag ~empty UL \ range(critical) as unmatched-unlock

(* Allow up to one unmatched LKW per location; more must deadlock *)
let UNMATCHED-LKW = LKW \ domain(critical)
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)

(* 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 =
	(*
	 * Convert the possible-rfe-noncrit-lf relation for e
	 * to a set of single edges
	 *)
	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

(*
 * 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)

(* Compute set of sets of possible rf edges for RU events *)
let all-possible-rf-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)

(* Final rf relation *)
let rf = rf | rf-lf | rf-ru

(* Generate all co relations, including LKW events but not UL *)
let co0 = co0 | ([IW] ; loc ; [LKW]) |
	(([LKW] ; loc ; [UNMATCHED-LKW]) \ [UNMATCHED-LKW])
include "cos-opt.cat"
let W = W | UL
let M = R | W

(* Merge UL events into co *)
let co = (co | critical | (critical^-1 ; co))+
let coe = co & ext
let coi = co & int

(* Merge LKR events into rf *)
let rf = rf | ([IW | UL] ; singlestep(co) ; lk-rmw^-1)
let rfe = rf & ext
let rfi = rf & int

let fr = rf^-1 ; co
let fre = fr & ext
let fri = fr & int

show co,rf,fr