1 // SPDX-License-Identifier: GPL-2.0+
2 (*
3 * Copyright (C) 2015 Jade Alglave <j.alglave@u
4 * Copyright (C) 2016 Luc Maranget <luc.marange
5 * Copyright (C) 2017 Alan Stern <stern@rowland
6 * Andrea Parri <parri.andre
7 *
8 * An earlier version of this file appeared in
9 * "Frightening small children and disconcerti
10 * in the Linux kernel" by Alglave, Maranget,
11 * which appeared in ASPLOS 2018.
12 *)
13
14 "Linux-kernel memory consistency model"
15
16 (*
17 * File "lock.cat" handles locks and is experi
18 * It can be replaced by include "cos.cat" for
19 *)
20
21 include "lock.cat"
22
23 (*******************)
24 (* Basic relations *)
25 (*******************)
26
27 (* Release Acquire *)
28 let acq-po = [Acquire] ; po ; [M]
29 let po-rel = [M] ; po ; [Release]
30 let po-unlock-lock-po = po ; [UL] ; (po|rf) ;
31
32 (* Fences *)
33 let R4rmb = R \ Noreturn (* Reads for w
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]
38 ([M] ; po? ; [RMW] ; fencerel(After-at
39 ([M] ; po? ; [LKW] ; fencerel(After-sp
40 (*
41 * Note: The po-unlock-lock-po relation only p
42 * successor, perhaps giving the impression th
43 * smp_mb__after_unlock_lock() fence only affe
44 * However, in a longer sequence of lock hando
45 * A-cumulative release fences of lock-release
46 * propagate to one of the involved CPUs befor
47 * the next CPU will also propagate to the fin
48 * to the CPU that executes the fence. Theref
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(
54 let gp = po ; [Sync-rcu | Sync-srcu] ; po?
55 let strong-fence = mb | gp
56
57 let nonrw-fence = strong-fence | po-rel | acq-
58 let fence = nonrw-fence | wmb | rmb
59 let barrier = fencerel(Barrier | Rmb | Wmb | M
60 Before-atomic | After-atomic |
61 Rcu-lock | Rcu-unlock | Srcu-l
62 (po ; [Release]) | ([Acquire] ; po)
63
64 (**********************************)
65 (* Fundamental coherence ordering *)
66 (**********************************)
67
68 (* Sequential Consistency Per Variable *)
69 let com = rf | co | fr
70 acyclic po-loc | com as coherence
71
72 (* Atomic Read-Modify-Write *)
73 empty rmw & (fre ; coe) as atomic
74
75 (**********************************)
76 (* Instruction execution ordering *)
77 (**********************************)
78
79 (* Preserved Program Order *)
80 let dep = addr | data
81 let rwdep = (dep | ctrl) ; [W]
82 let overwrite = co | fr
83 let to-w = rwdep | (overwrite & int) | (addr ;
84 let to-r = (addr ; [R]) | (dep ; [Marked] ; rf
85 let ppo = to-r | to-w | (fence & int) | (po-un
86
87 (* Propagation: Ordering from release operatio
88 let A-cumul(r) = (rfe ; [Marked])? ; r
89 let rmw-sequence = (rf ; rmw)*
90 let cumul-fence = [Marked] ; (A-cumul(strong-f
91 po-unlock-lock-po) ; [Marked] ; rmw-se
92 let prop = [Marked] ; (overwrite & ext)? ; cum
93 [Marked] ; rfe? ; [Marked]
94
95 (*
96 * Happens Before: Ordering from the passage o
97 * No fences needed here for prop because rela
98 *)
99 let hb = [Marked] ; (ppo | rfe | ((prop \ id)
100 acyclic hb as happens-before
101
102 (****************************************)
103 (* Write and fence propagation ordering *)
104 (****************************************)
105
106 (* Propagation: Each non-rf link needs a stron
107 let pb = prop ; strong-fence ; hb* ; [Marked]
108 acyclic pb as propagation
109
110 (*******)
111 (* RCU *)
112 (*******)
113
114 (*
115 * Effects of read-side critical sections proc
116 * or srcu_read_unlock() backwards on the one
117 * rcu_read_lock() or srcu_read_lock() forward
118 *
119 * In the definition of rcu-fence below, the p
120 * of each disjunct and the po? term at the ri
121 * out. They have been moved into the definit
122 * This was necessary in order to apply the "&
123 *)
124 let rcu-gp = [Sync-rcu] (* Compare wit
125 let srcu-gp = [Sync-srcu]
126 let rcu-rscsi = rcu-rscs^-1
127 let srcu-rscsi = srcu-rscs^-1
128
129 (*
130 * The synchronize_rcu() strong fence is speci
131 * one but two non-rf relations, but only in c
132 * read-side critical section.
133 *)
134 let rcu-link = po? ; hb* ; pb* ; prop ; po
135
136 (*
137 * Any sequence containing at least as many gr
138 * critical sections (joined by rcu-link) indu
139 * inter-CPU strong fence.
140 * Likewise for SRCU grace periods and read-si
141 * the synchronize_srcu() and srcu_read_[un]lo
142 * struct srcu_struct location.
143 *)
144 let rec rcu-order = rcu-gp | srcu-gp |
145 (rcu-gp ; rcu-link ; rcu-rscsi) |
146 ((srcu-gp ; rcu-link ; srcu-rscsi) & l
147 (rcu-rscsi ; rcu-link ; rcu-gp) |
148 ((srcu-rscsi ; rcu-link ; srcu-gp) & l
149 (rcu-gp ; rcu-link ; rcu-order ; rcu-l
150 ((srcu-gp ; rcu-link ; rcu-order ; rcu
151 (rcu-rscsi ; rcu-link ; rcu-order ; rc
152 ((srcu-rscsi ; rcu-link ; rcu-order ;
153 (rcu-order ; rcu-link ; rcu-order)
154 let rcu-fence = po ; rcu-order ; po?
155 let fence = fence | rcu-fence
156 let strong-fence = strong-fence | rcu-fence
157
158 (* rb orders instructions just as pb does *)
159 let rb = prop ; rcu-fence ; hb* ; pb* ; [Marke
160
161 irreflexive rb as rcu
162
163 (*
164 * The happens-before, propagation, and rcu co
165 * expressions of temporal ordering. They cou
166 * a single constraint on an "executes-before"
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
177 let mixed-accesses = ([Plain & W] ; (po-loc \
178 ([Marked] ; (po-loc \ barrier) ; [Plai
179 flag ~empty mixed-accesses as mixed-accesses
180
181 (* Executes-before and visibility *)
182 let xbstar = (hb | pb | rb)*
183 let vis = cumul-fence* ; rfe? ; [Marked] ;
184 ((strong-fence ; [Marked] ; xbstar) |
185
186 (* Boundaries for lifetimes of plain accesses
187 let w-pre-bounded = [Marked] ; (addr | fence)?
188 let r-pre-bounded = [Marked] ; (addr | nonrw-f
189 ([R4rmb] ; fencerel(Rmb) ; [~Noreturn]
190 let w-post-bounded = fence? ; [Marked] ; rmw-s
191 let r-post-bounded = (nonrw-fence | ([~Noretur
192 [Marked]
193
194 (* Visibility and executes-before for plain ac
195 let ww-vis = fence | (strong-fence ; xbstar ;
196 (w-post-bounded ; vis ; w-pre-bounded)
197 let wr-vis = fence | (strong-fence ; xbstar ;
198 (w-post-bounded ; vis ; r-pre-bounded)
199 let rw-xbstar = fence | (r-post-bounded ; xbst
200
201 (* Potential races *)
202 let pre-race = ext & ((Plain * M) | ((M \ IW)
203
204 (* Coherence requirements for plain accesses *
205 let wr-incoh = pre-race & rf & rw-xbstar^-1
206 let rw-incoh = pre-race & fr & wr-vis^-1
207 let ww-incoh = pre-race & co & ww-vis^-1
208 empty (wr-incoh | rw-incoh | ww-incoh) as plai
209
210 (* Actual races *)
211 let ww-nonrace = ww-vis & ((Marked * W) | rw-x
212 let ww-race = (pre-race & co) \ ww-nonrace
213 let wr-race = (pre-race & (co? ; rf)) \ wr-vis
214 let rw-race = (pre-race & fr) \ rw-xbstar
215
216 flag ~empty (ww-race | wr-race | rw-race) as d
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