1// SPDX-License-Identifier: GPL-2.0+ 2(* 3 * Copyright (C) 2015 Jade Alglave <j.alglave@ucl.ac.uk>, 4 * Copyright (C) 2016 Luc Maranget <luc.maranget@inria.fr> for Inria 5 * Copyright (C) 2017 Alan Stern <stern@rowland.harvard.edu>, 6 * Andrea Parri <parri.andrea@gmail.com> 7 * 8 * An earlier version of this file appeared in the companion webpage for 9 * "Frightening small children and disconcerting grown-ups: Concurrency 10 * in the Linux kernel" by Alglave, Maranget, McKenney, Parri, and Stern, 11 * which appeared in ASPLOS 2018. 12 *) 13 14"Linux-kernel memory consistency model" 15 16(* 17 * File "lock.cat" handles locks and is experimental. 18 * It can be replaced by include "cos.cat" for tests that do not use locks. 19 *) 20 21include "lock.cat" 22 23(*******************) 24(* Basic relations *) 25(*******************) 26 27(* Fences *) 28let rmb = [R \ Noreturn] ; fencerel(Rmb) ; [R \ Noreturn] 29let wmb = [W] ; fencerel(Wmb) ; [W] 30let mb = ([M] ; fencerel(Mb) ; [M]) | 31 ([M] ; fencerel(Before-atomic) ; [RMW] ; po? ; [M]) | 32 ([M] ; po? ; [RMW] ; fencerel(After-atomic) ; [M]) | 33 ([M] ; po? ; [LKW] ; fencerel(After-spinlock) ; [M]) | 34 ([M] ; po ; [UL] ; (co | po) ; [LKW] ; 35 fencerel(After-unlock-lock) ; [M]) 36let gp = po ; [Sync-rcu] ; po? 37 38let strong-fence = mb | gp 39 40(* Release Acquire *) 41let acq-po = [Acquire] ; po ; [M] 42let po-rel = [M] ; po ; [Release] 43let po-unlock-rf-lock-po = po ; [UL] ; rf ; [LKR] ; po 44 45(**********************************) 46(* Fundamental coherence ordering *) 47(**********************************) 48 49(* Sequential Consistency Per Variable *) 50let com = rf | co | fr 51acyclic po-loc | com as coherence 52 53(* Atomic Read-Modify-Write *) 54empty rmw & (fre ; coe) as atomic 55 56(**********************************) 57(* Instruction execution ordering *) 58(**********************************) 59 60(* Preserved Program Order *) 61let dep = addr | data 62let rwdep = (dep | ctrl) ; [W] 63let overwrite = co | fr 64let to-w = rwdep | (overwrite & int) 65let to-r = addr | (dep ; rfi) 66let fence = strong-fence | wmb | po-rel | rmb | acq-po 67let ppo = to-r | to-w | fence | (po-unlock-rf-lock-po & int) 68 69(* Propagation: Ordering from release operations and strong fences. *) 70let A-cumul(r) = rfe? ; r 71let cumul-fence = A-cumul(strong-fence | po-rel) | wmb | po-unlock-rf-lock-po 72let prop = (overwrite & ext)? ; cumul-fence* ; rfe? 73 74(* 75 * Happens Before: Ordering from the passage of time. 76 * No fences needed here for prop because relation confined to one process. 77 *) 78let hb = ppo | rfe | ((prop \ id) & int) 79acyclic hb as happens-before 80 81(****************************************) 82(* Write and fence propagation ordering *) 83(****************************************) 84 85(* Propagation: Each non-rf link needs a strong fence. *) 86let pb = prop ; strong-fence ; hb* 87acyclic pb as propagation 88 89(*******) 90(* RCU *) 91(*******) 92 93(* 94 * Effect of read-side critical section proceeds from the rcu_read_lock() 95 * onward on the one hand and from the rcu_read_unlock() backwards on the 96 * other hand. 97 *) 98let rscs = po ; crit^-1 ; po? 99 100(* 101 * The synchronize_rcu() strong fence is special in that it can order not 102 * one but two non-rf relations, but only in conjunction with an RCU 103 * read-side critical section. 104 *) 105let rcu-link = hb* ; pb* ; prop 106 107(* 108 * Any sequence containing at least as many grace periods as RCU read-side 109 * critical sections (joined by rcu-link) acts as a generalized strong fence. 110 *) 111let rec rcu-fence = gp | 112 (gp ; rcu-link ; rscs) | 113 (rscs ; rcu-link ; gp) | 114 (gp ; rcu-link ; rcu-fence ; rcu-link ; rscs) | 115 (rscs ; rcu-link ; rcu-fence ; rcu-link ; gp) | 116 (rcu-fence ; rcu-link ; rcu-fence) 117 118(* rb orders instructions just as pb does *) 119let rb = prop ; rcu-fence ; hb* ; pb* 120 121irreflexive rb as rcu 122 123(* 124 * The happens-before, propagation, and rcu constraints are all 125 * expressions of temporal ordering. They could be replaced by 126 * a single constraint on an "executes-before" relation, xb: 127 * 128 * let xb = hb | pb | rb 129 * acyclic xb as executes-before 130 *) 131