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// SPDX-License-Identifier: GPL-2.0+
(*
* 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>,
* Andrea Parri <parri.andrea@gmail.com>
*
* An earlier version of this file appears in the companion webpage for
* "Frightening small children and disconcerting grown-ups: Concurrency
* in the Linux kernel" by Alglave, Maranget, McKenney, Parri, and Stern,
* which is to appear in ASPLOS 2018.
*)
"Linux-kernel memory consistency model"
(*
* File "lock.cat" handles locks and is experimental.
* It can be replaced by include "cos.cat" for tests that do not use locks.
*)
include "lock.cat"
(*******************)
(* Basic relations *)
(*******************)
(* Fences *)
let rmb = [R \ Noreturn] ; fencerel(Rmb) ; [R \ Noreturn]
let wmb = [W] ; fencerel(Wmb) ; [W]
let mb = ([M] ; fencerel(Mb) ; [M]) |
([M] ; fencerel(Before-atomic) ; [RMW] ; po? ; [M]) |
([M] ; po? ; [RMW] ; fencerel(After-atomic) ; [M]) |
([M] ; po? ; [LKW] ; fencerel(After-spinlock) ; [M])
let gp = po ; [Sync-rcu] ; po?
let strong-fence = mb | gp
(* Release Acquire *)
let acq-po = [Acquire] ; po ; [M]
let po-rel = [M] ; po ; [Release]
let rfi-rel-acq = [Release] ; rfi ; [Acquire]
(**********************************)
(* Fundamental coherence ordering *)
(**********************************)
(* Sequential Consistency Per Variable *)
let com = rf | co | fr
acyclic po-loc | com as coherence
(* Atomic Read-Modify-Write *)
empty rmw & (fre ; coe) as atomic
(**********************************)
(* Instruction execution ordering *)
(**********************************)
(* Preserved Program Order *)
let dep = addr | data
let rwdep = (dep | ctrl) ; [W]
let overwrite = co | fr
let to-w = rwdep | (overwrite & int)
let to-r = addr | (dep ; rfi) | rfi-rel-acq
let fence = strong-fence | wmb | po-rel | rmb | acq-po
let ppo = to-r | to-w | fence
(* Propagation: Ordering from release operations and strong fences. *)
let A-cumul(r) = rfe? ; r
let cumul-fence = A-cumul(strong-fence | po-rel) | wmb
let prop = (overwrite & ext)? ; cumul-fence* ; rfe?
(*
* Happens Before: Ordering from the passage of time.
* No fences needed here for prop because relation confined to one process.
*)
let hb = ppo | rfe | ((prop \ id) & int)
acyclic hb as happens-before
(****************************************)
(* Write and fence propagation ordering *)
(****************************************)
(* Propagation: Each non-rf link needs a strong fence. *)
let pb = prop ; strong-fence ; hb*
acyclic pb as propagation
(*******)
(* RCU *)
(*******)
(*
* Effect of read-side critical section proceeds from the rcu_read_lock()
* onward on the one hand and from the rcu_read_unlock() backwards on the
* other hand.
*)
let rscs = po ; crit^-1 ; po?
(*
* The synchronize_rcu() strong fence is special in that it can order not
* one but two non-rf relations, but only in conjunction with an RCU
* read-side critical section.
*)
let link = hb* ; pb* ; prop
(* Chains that affect the RCU grace-period guarantee *)
let gp-link = gp ; link
let rscs-link = rscs ; link
(*
* A cycle containing at least as many grace periods as RCU read-side
* critical sections is forbidden.
*)
let rec rcu-path =
gp-link |
(gp-link ; rscs-link) |
(rscs-link ; gp-link) |
(rcu-path ; rcu-path) |
(gp-link ; rcu-path ; rscs-link) |
(rscs-link ; rcu-path ; gp-link)
irreflexive rcu-path as rcu
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