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-lock-po = po ; [UL] ; (po|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-lock-po & int) 74 75(* Propagation: Ordering from release operations and strong fences. *) 76let A-cumul(r) = (rfe ; [Marked])? ; r 77let rmw-sequence = (rf ; rmw)* 78let cumul-fence = [Marked] ; (A-cumul(strong-fence | po-rel) | wmb | 79 po-unlock-lock-po) ; [Marked] ; rmw-sequence 80let prop = [Marked] ; (overwrite & ext)? ; cumul-fence* ; 81 [Marked] ; rfe? ; [Marked] 82 83(* 84 * Happens Before: Ordering from the passage of time. 85 * No fences needed here for prop because relation confined to one process. 86 *) 87let hb = [Marked] ; (ppo | rfe | ((prop \ id) & int)) ; [Marked] 88acyclic hb as happens-before 89 90(****************************************) 91(* Write and fence propagation ordering *) 92(****************************************) 93 94(* Propagation: Each non-rf link needs a strong fence. *) 95let pb = prop ; strong-fence ; hb* ; [Marked] 96acyclic pb as propagation 97 98(*******) 99(* RCU *) 100(*******) 101 102(* 103 * Effects of read-side critical sections proceed from the rcu_read_unlock() 104 * or srcu_read_unlock() backwards on the one hand, and from the 105 * rcu_read_lock() or srcu_read_lock() forwards on the other hand. 106 * 107 * In the definition of rcu-fence below, the po term at the left-hand side 108 * of each disjunct and the po? term at the right-hand end have been factored 109 * out. They have been moved into the definitions of rcu-link and rb. 110 * This was necessary in order to apply the "& loc" tests correctly. 111 *) 112let rcu-gp = [Sync-rcu] (* Compare with gp *) 113let srcu-gp = [Sync-srcu] 114let rcu-rscsi = rcu-rscs^-1 115let srcu-rscsi = srcu-rscs^-1 116 117(* 118 * The synchronize_rcu() strong fence is special in that it can order not 119 * one but two non-rf relations, but only in conjunction with an RCU 120 * read-side critical section. 121 *) 122let rcu-link = po? ; hb* ; pb* ; prop ; po 123 124(* 125 * Any sequence containing at least as many grace periods as RCU read-side 126 * critical sections (joined by rcu-link) induces order like a generalized 127 * inter-CPU strong fence. 128 * Likewise for SRCU grace periods and read-side critical sections, provided 129 * the synchronize_srcu() and srcu_read_[un]lock() calls refer to the same 130 * struct srcu_struct location. 131 *) 132let rec rcu-order = rcu-gp | srcu-gp | 133 (rcu-gp ; rcu-link ; rcu-rscsi) | 134 ((srcu-gp ; rcu-link ; srcu-rscsi) & loc) | 135 (rcu-rscsi ; rcu-link ; rcu-gp) | 136 ((srcu-rscsi ; rcu-link ; srcu-gp) & loc) | 137 (rcu-gp ; rcu-link ; rcu-order ; rcu-link ; rcu-rscsi) | 138 ((srcu-gp ; rcu-link ; rcu-order ; rcu-link ; srcu-rscsi) & loc) | 139 (rcu-rscsi ; rcu-link ; rcu-order ; rcu-link ; rcu-gp) | 140 ((srcu-rscsi ; rcu-link ; rcu-order ; rcu-link ; srcu-gp) & loc) | 141 (rcu-order ; rcu-link ; rcu-order) 142let rcu-fence = po ; rcu-order ; po? 143let fence = fence | rcu-fence 144let strong-fence = strong-fence | rcu-fence 145 146(* rb orders instructions just as pb does *) 147let rb = prop ; rcu-fence ; hb* ; pb* ; [Marked] 148 149irreflexive rb as rcu 150 151(* 152 * The happens-before, propagation, and rcu constraints are all 153 * expressions of temporal ordering. They could be replaced by 154 * a single constraint on an "executes-before" relation, xb: 155 * 156 * let xb = hb | pb | rb 157 * acyclic xb as executes-before 158 *) 159 160(*********************************) 161(* Plain accesses and data races *) 162(*********************************) 163 164(* Warn about plain writes and marked accesses in the same region *) 165let mixed-accesses = ([Plain & W] ; (po-loc \ barrier) ; [Marked]) | 166 ([Marked] ; (po-loc \ barrier) ; [Plain & W]) 167flag ~empty mixed-accesses as mixed-accesses 168 169(* Executes-before and visibility *) 170let xbstar = (hb | pb | rb)* 171let vis = cumul-fence* ; rfe? ; [Marked] ; 172 ((strong-fence ; [Marked] ; xbstar) | (xbstar & int)) 173 174(* Boundaries for lifetimes of plain accesses *) 175let w-pre-bounded = [Marked] ; (addr | fence)? 176let r-pre-bounded = [Marked] ; (addr | nonrw-fence | 177 ([R4rmb] ; fencerel(Rmb) ; [~Noreturn]))? 178let w-post-bounded = fence? ; [Marked] ; rmw-sequence 179let r-post-bounded = (nonrw-fence | ([~Noreturn] ; fencerel(Rmb) ; [R4rmb]))? ; 180 [Marked] 181 182(* Visibility and executes-before for plain accesses *) 183let ww-vis = fence | (strong-fence ; xbstar ; w-pre-bounded) | 184 (w-post-bounded ; vis ; w-pre-bounded) 185let wr-vis = fence | (strong-fence ; xbstar ; r-pre-bounded) | 186 (w-post-bounded ; vis ; r-pre-bounded) 187let rw-xbstar = fence | (r-post-bounded ; xbstar ; w-pre-bounded) 188 189(* Potential races *) 190let pre-race = ext & ((Plain * M) | ((M \ IW) * Plain)) 191 192(* Coherence requirements for plain accesses *) 193let wr-incoh = pre-race & rf & rw-xbstar^-1 194let rw-incoh = pre-race & fr & wr-vis^-1 195let ww-incoh = pre-race & co & ww-vis^-1 196empty (wr-incoh | rw-incoh | ww-incoh) as plain-coherence 197 198(* Actual races *) 199let ww-nonrace = ww-vis & ((Marked * W) | rw-xbstar) & ((W * Marked) | wr-vis) 200let ww-race = (pre-race & co) \ ww-nonrace 201let wr-race = (pre-race & (co? ; rf)) \ wr-vis \ rw-xbstar^-1 202let rw-race = (pre-race & fr) \ rw-xbstar 203 204flag ~empty (ww-race | wr-race | rw-race) as data-race 205