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(* Release Acquire *) 28let acq-po = [Acquire] ; po ; [M] 29let po-rel = [M] ; po ; [Release] 30let po-unlock-rf-lock-po = po ; [UL] ; rf ; [LKR] ; po 31 32(* Fences *) 33let R4rmb = R \ Noreturn (* Reads for which rmb works *) 34let rmb = [R4rmb] ; fencerel(Rmb) ; [R4rmb] 35let wmb = [W] ; fencerel(Wmb) ; [W] 36let mb = ([M] ; fencerel(Mb) ; [M]) | 37 ([M] ; fencerel(Before-atomic) ; [RMW] ; po? ; [M]) | 38 ([M] ; po? ; [RMW] ; fencerel(After-atomic) ; [M]) | 39 ([M] ; po? ; [LKW] ; fencerel(After-spinlock) ; [M]) | 40 ([M] ; po ; [UL] ; (co | po) ; [LKW] ; 41 fencerel(After-unlock-lock) ; [M]) 42let gp = po ; [Sync-rcu | Sync-srcu] ; po? 43let strong-fence = mb | gp 44 45let nonrw-fence = strong-fence | po-rel | acq-po 46let fence = nonrw-fence | wmb | rmb 47let barrier = fencerel(Barrier | Rmb | Wmb | Mb | Sync-rcu | Sync-srcu | 48 Before-atomic | After-atomic | Acquire | Release | 49 Rcu-lock | Rcu-unlock | Srcu-lock | Srcu-unlock) | 50 (po ; [Release]) | ([Acquire] ; po) 51 52(**********************************) 53(* Fundamental coherence ordering *) 54(**********************************) 55 56(* Sequential Consistency Per Variable *) 57let com = rf | co | fr 58acyclic po-loc | com as coherence 59 60(* Atomic Read-Modify-Write *) 61empty rmw & (fre ; coe) as atomic 62 63(**********************************) 64(* Instruction execution ordering *) 65(**********************************) 66 67(* Preserved Program Order *) 68let dep = addr | data 69let rwdep = (dep | ctrl) ; [W] 70let overwrite = co | fr 71let to-w = rwdep | (overwrite & int) | (addr ; [Plain] ; wmb) 72let to-r = addr | (dep ; [Marked] ; rfi) 73let ppo = to-r | to-w | fence | (po-unlock-rf-lock-po & int) 74 75(* Propagation: Ordering from release operations and strong fences. *) 76let A-cumul(r) = (rfe ; [Marked])? ; r 77let cumul-fence = [Marked] ; (A-cumul(strong-fence | po-rel) | wmb | 78 po-unlock-rf-lock-po) ; [Marked] 79let prop = [Marked] ; (overwrite & ext)? ; cumul-fence* ; 80 [Marked] ; rfe? ; [Marked] 81 82(* 83 * Happens Before: Ordering from the passage of time. 84 * No fences needed here for prop because relation confined to one process. 85 *) 86let hb = [Marked] ; (ppo | rfe | ((prop \ id) & int)) ; [Marked] 87acyclic hb as happens-before 88 89(****************************************) 90(* Write and fence propagation ordering *) 91(****************************************) 92 93(* Propagation: Each non-rf link needs a strong fence. *) 94let pb = prop ; strong-fence ; hb* ; [Marked] 95acyclic pb as propagation 96 97(*******) 98(* RCU *) 99(*******) 100 101(* 102 * Effects of read-side critical sections proceed from the rcu_read_unlock() 103 * or srcu_read_unlock() backwards on the one hand, and from the 104 * rcu_read_lock() or srcu_read_lock() forwards on the other hand. 105 * 106 * In the definition of rcu-fence below, the po term at the left-hand side 107 * of each disjunct and the po? term at the right-hand end have been factored 108 * out. They have been moved into the definitions of rcu-link and rb. 109 * This was necessary in order to apply the "& loc" tests correctly. 110 *) 111let rcu-gp = [Sync-rcu] (* Compare with gp *) 112let srcu-gp = [Sync-srcu] 113let rcu-rscsi = rcu-rscs^-1 114let srcu-rscsi = srcu-rscs^-1 115 116(* 117 * The synchronize_rcu() strong fence is special in that it can order not 118 * one but two non-rf relations, but only in conjunction with an RCU 119 * read-side critical section. 120 *) 121let rcu-link = po? ; hb* ; pb* ; prop ; po 122 123(* 124 * Any sequence containing at least as many grace periods as RCU read-side 125 * critical sections (joined by rcu-link) induces order like a generalized 126 * inter-CPU strong fence. 127 * Likewise for SRCU grace periods and read-side critical sections, provided 128 * the synchronize_srcu() and srcu_read_[un]lock() calls refer to the same 129 * struct srcu_struct location. 130 *) 131let rec rcu-order = rcu-gp | srcu-gp | 132 (rcu-gp ; rcu-link ; rcu-rscsi) | 133 ((srcu-gp ; rcu-link ; srcu-rscsi) & loc) | 134 (rcu-rscsi ; rcu-link ; rcu-gp) | 135 ((srcu-rscsi ; rcu-link ; srcu-gp) & loc) | 136 (rcu-gp ; rcu-link ; rcu-order ; rcu-link ; rcu-rscsi) | 137 ((srcu-gp ; rcu-link ; rcu-order ; rcu-link ; srcu-rscsi) & loc) | 138 (rcu-rscsi ; rcu-link ; rcu-order ; rcu-link ; rcu-gp) | 139 ((srcu-rscsi ; rcu-link ; rcu-order ; rcu-link ; srcu-gp) & loc) | 140 (rcu-order ; rcu-link ; rcu-order) 141let rcu-fence = po ; rcu-order ; po? 142let fence = fence | rcu-fence 143let strong-fence = strong-fence | rcu-fence 144 145(* rb orders instructions just as pb does *) 146let rb = prop ; rcu-fence ; hb* ; pb* ; [Marked] 147 148irreflexive rb as rcu 149 150(* 151 * The happens-before, propagation, and rcu constraints are all 152 * expressions of temporal ordering. They could be replaced by 153 * a single constraint on an "executes-before" relation, xb: 154 * 155 * let xb = hb | pb | rb 156 * acyclic xb as executes-before 157 *) 158 159(*********************************) 160(* Plain accesses and data races *) 161(*********************************) 162 163(* Warn about plain writes and marked accesses in the same region *) 164let mixed-accesses = ([Plain & W] ; (po-loc \ barrier) ; [Marked]) | 165 ([Marked] ; (po-loc \ barrier) ; [Plain & W]) 166flag ~empty mixed-accesses as mixed-accesses 167 168(* Executes-before and visibility *) 169let xbstar = (hb | pb | rb)* 170let vis = cumul-fence* ; rfe? ; [Marked] ; 171 ((strong-fence ; [Marked] ; xbstar) | (xbstar & int)) 172 173(* Boundaries for lifetimes of plain accesses *) 174let w-pre-bounded = [Marked] ; (addr | fence)? 175let r-pre-bounded = [Marked] ; (addr | nonrw-fence | 176 ([R4rmb] ; fencerel(Rmb) ; [~Noreturn]))? 177let w-post-bounded = fence? ; [Marked] 178let r-post-bounded = (nonrw-fence | ([~Noreturn] ; fencerel(Rmb) ; [R4rmb]))? ; 179 [Marked] 180 181(* Visibility and executes-before for plain accesses *) 182let ww-vis = fence | (strong-fence ; xbstar ; w-pre-bounded) | 183 (w-post-bounded ; vis ; w-pre-bounded) 184let wr-vis = fence | (strong-fence ; xbstar ; r-pre-bounded) | 185 (w-post-bounded ; vis ; r-pre-bounded) 186let rw-xbstar = fence | (r-post-bounded ; xbstar ; w-pre-bounded) 187 188(* Potential races *) 189let pre-race = ext & ((Plain * M) | ((M \ IW) * Plain)) 190 191(* Coherence requirements for plain accesses *) 192let wr-incoh = pre-race & rf & rw-xbstar^-1 193let rw-incoh = pre-race & fr & wr-vis^-1 194let ww-incoh = pre-race & co & ww-vis^-1 195empty (wr-incoh | rw-incoh | ww-incoh) as plain-coherence 196 197(* Actual races *) 198let ww-nonrace = ww-vis & ((Marked * W) | rw-xbstar) & ((W * Marked) | wr-vis) 199let ww-race = (pre-race & co) \ ww-nonrace 200let wr-race = (pre-race & (co? ; rf)) \ wr-vis \ rw-xbstar^-1 201let rw-race = (pre-race & fr) \ rw-xbstar 202 203flag ~empty (ww-race | wr-race | rw-race) as data-race 204