linux/tools/memory-model/linux-kernel.cat
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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 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