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(* 41 * Note: The po-unlock-lock-po relation only passes the lock to the direct 42 * successor, perhaps giving the impression that the ordering of the 43 * smp_mb__after_unlock_lock() fence only affects a single lock handover. 44 * However, in a longer sequence of lock handovers, the implicit 45 * A-cumulative release fences of lock-release ensure that any stores that 46 * propagate to one of the involved CPUs before it hands over the lock to 47 * the next CPU will also propagate to the final CPU handing over the lock 48 * to the CPU that executes the fence. Therefore, all those stores are 49 * also affected by the fence. 50 *) 51 ([M] ; po-unlock-lock-po ; 52 [After-unlock-lock] ; po ; [M]) | 53 ([M] ; po? ; [Srcu-unlock] ; fencerel(After-srcu-read-unlock) ; [M]) 54let gp = po ; [Sync-rcu | Sync-srcu] ; po? 55let strong-fence = mb | gp 56 57let nonrw-fence = strong-fence | po-rel | acq-po 58let fence = nonrw-fence | wmb | rmb 59let barrier = fencerel(Barrier | Rmb | Wmb | Mb | Sync-rcu | Sync-srcu | 60 Before-atomic | After-atomic | Acquire | Release | 61 Rcu-lock | Rcu-unlock | Srcu-lock | Srcu-unlock) | 62 (po ; [Release]) | ([Acquire] ; po) 63 64(**********************************) 65(* Fundamental coherence ordering *) 66(**********************************) 67 68(* Sequential Consistency Per Variable *) 69let com = rf | co | fr 70acyclic po-loc | com as coherence 71 72(* Atomic Read-Modify-Write *) 73empty rmw & (fre ; coe) as atomic 74 75(**********************************) 76(* Instruction execution ordering *) 77(**********************************) 78 79(* Preserved Program Order *) 80let dep = addr | data 81let rwdep = (dep | ctrl) ; [W] 82let overwrite = co | fr 83let to-w = rwdep | (overwrite & int) | (addr ; [Plain] ; wmb) 84let to-r = (addr ; [R]) | (dep ; [Marked] ; rfi) 85let ppo = to-r | to-w | (fence & int) | (po-unlock-lock-po & int) 86 87(* Propagation: Ordering from release operations and strong fences. *) 88let A-cumul(r) = (rfe ; [Marked])? ; r 89let rmw-sequence = (rf ; rmw)* 90let cumul-fence = [Marked] ; (A-cumul(strong-fence | po-rel) | wmb | 91 po-unlock-lock-po) ; [Marked] ; rmw-sequence 92let prop = [Marked] ; (overwrite & ext)? ; cumul-fence* ; 93 [Marked] ; rfe? ; [Marked] 94 95(* 96 * Happens Before: Ordering from the passage of time. 97 * No fences needed here for prop because relation confined to one process. 98 *) 99let hb = [Marked] ; (ppo | rfe | ((prop \ id) & int)) ; [Marked] 100acyclic hb as happens-before 101 102(****************************************) 103(* Write and fence propagation ordering *) 104(****************************************) 105 106(* Propagation: Each non-rf link needs a strong fence. *) 107let pb = prop ; strong-fence ; hb* ; [Marked] 108acyclic pb as propagation 109 110(*******) 111(* RCU *) 112(*******) 113 114(* 115 * Effects of read-side critical sections proceed from the rcu_read_unlock() 116 * or srcu_read_unlock() backwards on the one hand, and from the 117 * rcu_read_lock() or srcu_read_lock() forwards on the other hand. 118 * 119 * In the definition of rcu-fence below, the po term at the left-hand side 120 * of each disjunct and the po? term at the right-hand end have been factored 121 * out. They have been moved into the definitions of rcu-link and rb. 122 * This was necessary in order to apply the "& loc" tests correctly. 123 *) 124let rcu-gp = [Sync-rcu] (* Compare with gp *) 125let srcu-gp = [Sync-srcu] 126let rcu-rscsi = rcu-rscs^-1 127let srcu-rscsi = srcu-rscs^-1 128 129(* 130 * The synchronize_rcu() strong fence is special in that it can order not 131 * one but two non-rf relations, but only in conjunction with an RCU 132 * read-side critical section. 133 *) 134let rcu-link = po? ; hb* ; pb* ; prop ; po 135 136(* 137 * Any sequence containing at least as many grace periods as RCU read-side 138 * critical sections (joined by rcu-link) induces order like a generalized 139 * inter-CPU strong fence. 140 * Likewise for SRCU grace periods and read-side critical sections, provided 141 * the synchronize_srcu() and srcu_read_[un]lock() calls refer to the same 142 * struct srcu_struct location. 143 *) 144let rec rcu-order = rcu-gp | srcu-gp | 145 (rcu-gp ; rcu-link ; rcu-rscsi) | 146 ((srcu-gp ; rcu-link ; srcu-rscsi) & loc) | 147 (rcu-rscsi ; rcu-link ; rcu-gp) | 148 ((srcu-rscsi ; rcu-link ; srcu-gp) & loc) | 149 (rcu-gp ; rcu-link ; rcu-order ; rcu-link ; rcu-rscsi) | 150 ((srcu-gp ; rcu-link ; rcu-order ; rcu-link ; srcu-rscsi) & loc) | 151 (rcu-rscsi ; rcu-link ; rcu-order ; rcu-link ; rcu-gp) | 152 ((srcu-rscsi ; rcu-link ; rcu-order ; rcu-link ; srcu-gp) & loc) | 153 (rcu-order ; rcu-link ; rcu-order) 154let rcu-fence = po ; rcu-order ; po? 155let fence = fence | rcu-fence 156let strong-fence = strong-fence | rcu-fence 157 158(* rb orders instructions just as pb does *) 159let rb = prop ; rcu-fence ; hb* ; pb* ; [Marked] 160 161irreflexive rb as rcu 162 163(* 164 * The happens-before, propagation, and rcu constraints are all 165 * expressions of temporal ordering. They could be replaced by 166 * a single constraint on an "executes-before" relation, xb: 167 * 168 * let xb = hb | pb | rb 169 * acyclic xb as executes-before 170 *) 171 172(*********************************) 173(* Plain accesses and data races *) 174(*********************************) 175 176(* Warn about plain writes and marked accesses in the same region *) 177let mixed-accesses = ([Plain & W] ; (po-loc \ barrier) ; [Marked]) | 178 ([Marked] ; (po-loc \ barrier) ; [Plain & W]) 179flag ~empty mixed-accesses as mixed-accesses 180 181(* Executes-before and visibility *) 182let xbstar = (hb | pb | rb)* 183let vis = cumul-fence* ; rfe? ; [Marked] ; 184 ((strong-fence ; [Marked] ; xbstar) | (xbstar & int)) 185 186(* Boundaries for lifetimes of plain accesses *) 187let w-pre-bounded = [Marked] ; (addr | fence)? 188let r-pre-bounded = [Marked] ; (addr | nonrw-fence | 189 ([R4rmb] ; fencerel(Rmb) ; [~Noreturn]))? 190let w-post-bounded = fence? ; [Marked] ; rmw-sequence 191let r-post-bounded = (nonrw-fence | ([~Noreturn] ; fencerel(Rmb) ; [R4rmb]))? ; 192 [Marked] 193 194(* Visibility and executes-before for plain accesses *) 195let ww-vis = fence | (strong-fence ; xbstar ; w-pre-bounded) | 196 (w-post-bounded ; vis ; w-pre-bounded) 197let wr-vis = fence | (strong-fence ; xbstar ; r-pre-bounded) | 198 (w-post-bounded ; vis ; r-pre-bounded) 199let rw-xbstar = fence | (r-post-bounded ; xbstar ; w-pre-bounded) 200 201(* Potential races *) 202let pre-race = ext & ((Plain * M) | ((M \ IW) * Plain)) 203 204(* Coherence requirements for plain accesses *) 205let wr-incoh = pre-race & rf & rw-xbstar^-1 206let rw-incoh = pre-race & fr & wr-vis^-1 207let ww-incoh = pre-race & co & ww-vis^-1 208empty (wr-incoh | rw-incoh | ww-incoh) as plain-coherence 209 210(* Actual races *) 211let ww-nonrace = ww-vis & ((Marked * W) | rw-xbstar) & ((W * Marked) | wr-vis) 212let ww-race = (pre-race & co) \ ww-nonrace 213let wr-race = (pre-race & (co? ; rf)) \ wr-vis \ rw-xbstar^-1 214let rw-race = (pre-race & fr) \ rw-xbstar 215 216flag ~empty (ww-race | wr-race | rw-race) as data-race 217