1 // SPDX-License-Identifier: GPL-2.0+
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>
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.
14 "Linux-kernel memory consistency model"
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.
28 let acq-po = [Acquire] ; po ; [M]
29 let po-rel = [M] ; po ; [Release]
30 let po-unlock-lock-po = po ; [UL] ; (po|rf) ; [LKR] ; po
33 let R4rmb = R \ Noreturn (* Reads for which rmb works *)
34 let rmb = [R4rmb] ; fencerel(Rmb) ; [R4rmb]
35 let wmb = [W] ; fencerel(Wmb) ; [W]
36 let 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])
42 let gp = po ; [Sync-rcu | Sync-srcu] ; po?
43 let strong-fence = mb | gp
45 let nonrw-fence = strong-fence | po-rel | acq-po
46 let fence = nonrw-fence | wmb | rmb
47 let 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)
52 (**********************************)
53 (* Fundamental coherence ordering *)
54 (**********************************)
56 (* Sequential Consistency Per Variable *)
57 let com = rf | co | fr
58 acyclic po-loc | com as coherence
60 (* Atomic Read-Modify-Write *)
61 empty rmw & (fre ; coe) as atomic
63 (**********************************)
64 (* Instruction execution ordering *)
65 (**********************************)
67 (* Preserved Program Order *)
69 let rwdep = (dep | ctrl) ; [W]
70 let overwrite = co | fr
71 let to-w = rwdep | (overwrite & int) | (addr ; [Plain] ; wmb)
72 let to-r = addr | (dep ; [Marked] ; rfi)
73 let ppo = to-r | to-w | fence | (po-unlock-lock-po & int)
75 (* Propagation: Ordering from release operations and strong fences. *)
76 let A-cumul(r) = (rfe ; [Marked])? ; r
77 let rmw-sequence = (rf ; rmw)*
78 let cumul-fence = [Marked] ; (A-cumul(strong-fence | po-rel) | wmb |
79 po-unlock-lock-po) ; [Marked] ; rmw-sequence
80 let prop = [Marked] ; (overwrite & ext)? ; cumul-fence* ;
81 [Marked] ; rfe? ; [Marked]
84 * Happens Before: Ordering from the passage of time.
85 * No fences needed here for prop because relation confined to one process.
87 let hb = [Marked] ; (ppo | rfe | ((prop \ id) & int)) ; [Marked]
88 acyclic hb as happens-before
90 (****************************************)
91 (* Write and fence propagation ordering *)
92 (****************************************)
94 (* Propagation: Each non-rf link needs a strong fence. *)
95 let pb = prop ; strong-fence ; hb* ; [Marked]
96 acyclic pb as propagation
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.
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.
112 let rcu-gp = [Sync-rcu] (* Compare with gp *)
113 let srcu-gp = [Sync-srcu]
114 let rcu-rscsi = rcu-rscs^-1
115 let srcu-rscsi = srcu-rscs^-1
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.
122 let rcu-link = po? ; hb* ; pb* ; prop ; po
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.
132 let 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)
142 let rcu-fence = po ; rcu-order ; po?
143 let fence = fence | rcu-fence
144 let strong-fence = strong-fence | rcu-fence
146 (* rb orders instructions just as pb does *)
147 let rb = prop ; rcu-fence ; hb* ; pb* ; [Marked]
149 irreflexive rb as rcu
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:
156 * let xb = hb | pb | rb
157 * acyclic xb as executes-before
160 (*********************************)
161 (* Plain accesses and data races *)
162 (*********************************)
164 (* Warn about plain writes and marked accesses in the same region *)
165 let mixed-accesses = ([Plain & W] ; (po-loc \ barrier) ; [Marked]) |
166 ([Marked] ; (po-loc \ barrier) ; [Plain & W])
167 flag ~empty mixed-accesses as mixed-accesses
169 (* Executes-before and visibility *)
170 let xbstar = (hb | pb | rb)*
171 let vis = cumul-fence* ; rfe? ; [Marked] ;
172 ((strong-fence ; [Marked] ; xbstar) | (xbstar & int))
174 (* Boundaries for lifetimes of plain accesses *)
175 let w-pre-bounded = [Marked] ; (addr | fence)?
176 let r-pre-bounded = [Marked] ; (addr | nonrw-fence |
177 ([R4rmb] ; fencerel(Rmb) ; [~Noreturn]))?
178 let w-post-bounded = fence? ; [Marked] ; rmw-sequence
179 let r-post-bounded = (nonrw-fence | ([~Noreturn] ; fencerel(Rmb) ; [R4rmb]))? ;
182 (* Visibility and executes-before for plain accesses *)
183 let ww-vis = fence | (strong-fence ; xbstar ; w-pre-bounded) |
184 (w-post-bounded ; vis ; w-pre-bounded)
185 let wr-vis = fence | (strong-fence ; xbstar ; r-pre-bounded) |
186 (w-post-bounded ; vis ; r-pre-bounded)
187 let rw-xbstar = fence | (r-post-bounded ; xbstar ; w-pre-bounded)
189 (* Potential races *)
190 let pre-race = ext & ((Plain * M) | ((M \ IW) * Plain))
192 (* Coherence requirements for plain accesses *)
193 let wr-incoh = pre-race & rf & rw-xbstar^-1
194 let rw-incoh = pre-race & fr & wr-vis^-1
195 let ww-incoh = pre-race & co & ww-vis^-1
196 empty (wr-incoh | rw-incoh | ww-incoh) as plain-coherence
199 let ww-nonrace = ww-vis & ((Marked * W) | rw-xbstar) & ((W * Marked) | wr-vis)
200 let ww-race = (pre-race & co) \ ww-nonrace
201 let wr-race = (pre-race & (co? ; rf)) \ wr-vis \ rw-xbstar^-1
202 let rw-race = (pre-race & fr) \ rw-xbstar
204 flag ~empty (ww-race | wr-race | rw-race) as data-race