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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 Inria5 * 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 for9 * "Frightening small children and disconcerting grown-ups: Concurrency10 * 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] ; po31 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 direct42 * successor, perhaps giving the impression that the ordering of the43 * smp_mb__after_unlock_lock() fence only affects a single lock handover.44 * However, in a longer sequence of lock handovers, the implicit45 * A-cumulative release fences of lock-release ensure that any stores that46 * propagate to one of the involved CPUs before it hands over the lock to47 * the next CPU will also propagate to the final CPU handing over the lock48 * to the CPU that executes the fence. Therefore, all those stores are49 * 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 | gp56 57let nonrw-fence = strong-fence | po-rel | acq-po58let fence = nonrw-fence | wmb | rmb59let 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 | fr70acyclic po-loc | com as coherence71 72(* Atomic Read-Modify-Write *)73empty rmw & (fre ; coe) as atomic74 75(**********************************)76(* Instruction execution ordering *)77(**********************************)78 79(* Preserved Program Order *)80let dep = addr | data81let rwdep = (dep | ctrl) ; [W]82let overwrite = co | fr83let 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])? ; r89let rmw-sequence = (rf ; rmw)*90let cumul-fence = [Marked] ; (A-cumul(strong-fence | po-rel) | wmb |91 po-unlock-lock-po) ; [Marked] ; rmw-sequence92let 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-before101 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 propagation109 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 the117 * 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 side120 * of each disjunct and the po? term at the right-hand end have been factored121 * 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^-1127let srcu-rscsi = srcu-rscs^-1128 129(*130 * The synchronize_rcu() strong fence is special in that it can order not131 * one but two non-rf relations, but only in conjunction with an RCU132 * read-side critical section.133 *)134let rcu-link = po? ; hb* ; pb* ; prop ; po135 136(*137 * Any sequence containing at least as many grace periods as RCU read-side138 * critical sections (joined by rcu-link) induces order like a generalized139 * inter-CPU strong fence.140 * Likewise for SRCU grace periods and read-side critical sections, provided141 * the synchronize_srcu() and srcu_read_[un]lock() calls refer to the same142 * 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-fence156let strong-fence = strong-fence | rcu-fence157 158(* rb orders instructions just as pb does *)159let rb = prop ; rcu-fence ; hb* ; pb* ; [Marked]160 161irreflexive rb as rcu162 163(*164 * The happens-before, propagation, and rcu constraints are all165 * expressions of temporal ordering. They could be replaced by166 * a single constraint on an "executes-before" relation, xb:167 *168 * let xb = hb | pb | rb169 * acyclic xb as executes-before170 *)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-accesses180 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-sequence191let 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^-1206let rw-incoh = pre-race & fr & wr-vis^-1207let ww-incoh = pre-race & co & ww-vis^-1208empty (wr-incoh | rw-incoh | ww-incoh) as plain-coherence209 210(* Actual races *)211let ww-nonrace = ww-vis & ((Marked * W) | rw-xbstar) & ((W * Marked) | wr-vis)212let ww-race = (pre-race & co) \ ww-nonrace213let wr-race = (pre-race & (co? ; rf)) \ wr-vis \ rw-xbstar^-1214let rw-race = (pre-race & fr) \ rw-xbstar215 216flag ~empty (ww-race | wr-race | rw-race) as data-race217