xref: /openbmc/linux/tools/memory-model/lock.cat (revision 8559183ccaec97454b2515ac426f113967256cf9)

// 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 *)
(*
 * Warning, crashes with herd7 versions strictly before 7.48.
 * spin_islocked is functional from version 7.49.
 *
 *)
include "cross.cat"

(* From lock reads to their partner lock writes *)
let lk-rmw = ([LKR] ; po-loc ; [LKW]) \ (po ; po)
let rmw = rmw | lk-rmw

(*
 * A paired 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 ; [domain(lk-rmw)]) \ (po-loc ; [UL] ; po-loc)
	as lock-nest

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

(* This will be allowed if we implement spin_is_locked() *)
flag ~empty LKR \ domain(lk-rmw) as unpaired-LKR

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

(* The final value of a spinlock should not be tested *)
flag ~empty [FW] ; loc ; [ALL-LOCKS] as lock-final

(*
 * Backward compatibility
 *)
let RL = try RL with emptyset (* defined herd7 >= 7.49 *)
let RU = try RU with emptyset (* defined herd7 >= 7.49 *)

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

(*
 * 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)

(* rfe 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.
   *)
  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))

(* Generate all rf relations for LF events *)
with rfe-lf from cross(all-possible-rfe-lf)
let rf-lf = rfe-lf | rfi-lf

(* Read from unlock, ie islocked returning false, slightly different *)

(* islocked returning false can read from the last po-previous unlock *)
let rfi-ru = ([UL] ; po-loc ; [RU]) \ ([UL] ; po-loc ; [LKW] ; po-loc)

(* any islocked returning false can read from any external unlock *)
let all-possible-rfe-ru =
   let possible-rfe-ru r =
     let pair-to-relation p = p ++ 0
     in map pair-to-relation (((UL|IW) * {r}) & loc & ext)
  in map possible-rfe-ru RU

with rfe-ru from cross(all-possible-rfe-ru)
let rf-ru = rfe-ru | rfi-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