1 // SPDX-License-Identifier: GPL-2.0+ 1 // SPDX-License-Identifier: GPL-2.0+
2 (* 2 (*
3 * Copyright (C) 2015 Jade Alglave <j.alglave@u 3 * Copyright (C) 2015 Jade Alglave <j.alglave@ucl.ac.uk>,
4 * Copyright (C) 2016 Luc Maranget <luc.marange 4 * Copyright (C) 2016 Luc Maranget <luc.maranget@inria.fr> for Inria
5 * Copyright (C) 2017 Alan Stern <stern@rowland 5 * Copyright (C) 2017 Alan Stern <stern@rowland.harvard.edu>,
6 * Andrea Parri <parri.andre 6 * Andrea Parri <parri.andrea@gmail.com>
7 * 7 *
8 * An earlier version of this file appeared in 8 * An earlier version of this file appeared in the companion webpage for
9 * "Frightening small children and disconcerti 9 * "Frightening small children and disconcerting grown-ups: Concurrency
10 * in the Linux kernel" by Alglave, Maranget, 10 * in the Linux kernel" by Alglave, Maranget, McKenney, Parri, and Stern,
11 * which appeared in ASPLOS 2018. 11 * which appeared in ASPLOS 2018.
12 *) 12 *)
13 13
14 "Linux-kernel memory consistency model" 14 "Linux-kernel memory consistency model"
15 15
16 (* 16 (*
17 * File "lock.cat" handles locks and is experi 17 * File "lock.cat" handles locks and is experimental.
18 * It can be replaced by include "cos.cat" for 18 * It can be replaced by include "cos.cat" for tests that do not use locks.
19 *) 19 *)
20 20
21 include "lock.cat" 21 include "lock.cat"
22 22
23 (*******************) 23 (*******************)
24 (* Basic relations *) 24 (* Basic relations *)
25 (*******************) 25 (*******************)
26 26
27 (* Release Acquire *) 27 (* Release Acquire *)
28 let acq-po = [Acquire] ; po ; [M] 28 let acq-po = [Acquire] ; po ; [M]
29 let po-rel = [M] ; po ; [Release] 29 let po-rel = [M] ; po ; [Release]
30 let po-unlock-lock-po = po ; [UL] ; (po|rf) ; 30 let po-unlock-lock-po = po ; [UL] ; (po|rf) ; [LKR] ; po
31 31
32 (* Fences *) 32 (* Fences *)
33 let R4rmb = R \ Noreturn (* Reads for w 33 let R4rmb = R \ Noreturn (* Reads for which rmb works *)
34 let rmb = [R4rmb] ; fencerel(Rmb) ; [R4rmb] 34 let rmb = [R4rmb] ; fencerel(Rmb) ; [R4rmb]
35 let wmb = [W] ; fencerel(Wmb) ; [W] 35 let wmb = [W] ; fencerel(Wmb) ; [W]
36 let mb = ([M] ; fencerel(Mb) ; [M]) | 36 let mb = ([M] ; fencerel(Mb) ; [M]) |
37 ([M] ; fencerel(Before-atomic) ; [RMW] 37 ([M] ; fencerel(Before-atomic) ; [RMW] ; po? ; [M]) |
38 ([M] ; po? ; [RMW] ; fencerel(After-at 38 ([M] ; po? ; [RMW] ; fencerel(After-atomic) ; [M]) |
39 ([M] ; po? ; [LKW] ; fencerel(After-sp 39 ([M] ; po? ; [LKW] ; fencerel(After-spinlock) ; [M]) |
40 (* 40 (*
41 * Note: The po-unlock-lock-po relation only p 41 * Note: The po-unlock-lock-po relation only passes the lock to the direct
42 * successor, perhaps giving the impression th 42 * successor, perhaps giving the impression that the ordering of the
43 * smp_mb__after_unlock_lock() fence only affe 43 * smp_mb__after_unlock_lock() fence only affects a single lock handover.
44 * However, in a longer sequence of lock hando 44 * However, in a longer sequence of lock handovers, the implicit
45 * A-cumulative release fences of lock-release 45 * A-cumulative release fences of lock-release ensure that any stores that
46 * propagate to one of the involved CPUs befor 46 * propagate to one of the involved CPUs before it hands over the lock to
47 * the next CPU will also propagate to the fin 47 * the next CPU will also propagate to the final CPU handing over the lock
48 * to the CPU that executes the fence. Theref 48 * to the CPU that executes the fence. Therefore, all those stores are
49 * also affected by the fence. 49 * also affected by the fence.
50 *) 50 *)
51 ([M] ; po-unlock-lock-po ; 51 ([M] ; po-unlock-lock-po ;
52 [After-unlock-lock] ; po ; [M] 52 [After-unlock-lock] ; po ; [M]) |
53 ([M] ; po? ; [Srcu-unlock] ; fencerel( 53 ([M] ; po? ; [Srcu-unlock] ; fencerel(After-srcu-read-unlock) ; [M])
54 let gp = po ; [Sync-rcu | Sync-srcu] ; po? 54 let gp = po ; [Sync-rcu | Sync-srcu] ; po?
55 let strong-fence = mb | gp 55 let strong-fence = mb | gp
56 56
57 let nonrw-fence = strong-fence | po-rel | acq- 57 let nonrw-fence = strong-fence | po-rel | acq-po
58 let fence = nonrw-fence | wmb | rmb 58 let fence = nonrw-fence | wmb | rmb
59 let barrier = fencerel(Barrier | Rmb | Wmb | M 59 let barrier = fencerel(Barrier | Rmb | Wmb | Mb | Sync-rcu | Sync-srcu |
60 Before-atomic | After-atomic | 60 Before-atomic | After-atomic | Acquire | Release |
61 Rcu-lock | Rcu-unlock | Srcu-l 61 Rcu-lock | Rcu-unlock | Srcu-lock | Srcu-unlock) |
62 (po ; [Release]) | ([Acquire] ; po) 62 (po ; [Release]) | ([Acquire] ; po)
63 63
64 (**********************************) 64 (**********************************)
65 (* Fundamental coherence ordering *) 65 (* Fundamental coherence ordering *)
66 (**********************************) 66 (**********************************)
67 67
68 (* Sequential Consistency Per Variable *) 68 (* Sequential Consistency Per Variable *)
69 let com = rf | co | fr 69 let com = rf | co | fr
70 acyclic po-loc | com as coherence 70 acyclic po-loc | com as coherence
71 71
72 (* Atomic Read-Modify-Write *) 72 (* Atomic Read-Modify-Write *)
73 empty rmw & (fre ; coe) as atomic 73 empty rmw & (fre ; coe) as atomic
74 74
75 (**********************************) 75 (**********************************)
76 (* Instruction execution ordering *) 76 (* Instruction execution ordering *)
77 (**********************************) 77 (**********************************)
78 78
79 (* Preserved Program Order *) 79 (* Preserved Program Order *)
80 let dep = addr | data 80 let dep = addr | data
81 let rwdep = (dep | ctrl) ; [W] 81 let rwdep = (dep | ctrl) ; [W]
82 let overwrite = co | fr 82 let overwrite = co | fr
83 let to-w = rwdep | (overwrite & int) | (addr ; 83 let to-w = rwdep | (overwrite & int) | (addr ; [Plain] ; wmb)
84 let to-r = (addr ; [R]) | (dep ; [Marked] ; rf 84 let to-r = (addr ; [R]) | (dep ; [Marked] ; rfi)
85 let ppo = to-r | to-w | (fence & int) | (po-un 85 let ppo = to-r | to-w | (fence & int) | (po-unlock-lock-po & int)
86 86
87 (* Propagation: Ordering from release operatio 87 (* Propagation: Ordering from release operations and strong fences. *)
88 let A-cumul(r) = (rfe ; [Marked])? ; r 88 let A-cumul(r) = (rfe ; [Marked])? ; r
89 let rmw-sequence = (rf ; rmw)* 89 let rmw-sequence = (rf ; rmw)*
90 let cumul-fence = [Marked] ; (A-cumul(strong-f 90 let cumul-fence = [Marked] ; (A-cumul(strong-fence | po-rel) | wmb |
91 po-unlock-lock-po) ; [Marked] ; rmw-se 91 po-unlock-lock-po) ; [Marked] ; rmw-sequence
92 let prop = [Marked] ; (overwrite & ext)? ; cum 92 let prop = [Marked] ; (overwrite & ext)? ; cumul-fence* ;
93 [Marked] ; rfe? ; [Marked] 93 [Marked] ; rfe? ; [Marked]
94 94
95 (* 95 (*
96 * Happens Before: Ordering from the passage o 96 * Happens Before: Ordering from the passage of time.
97 * No fences needed here for prop because rela 97 * No fences needed here for prop because relation confined to one process.
98 *) 98 *)
99 let hb = [Marked] ; (ppo | rfe | ((prop \ id) 99 let hb = [Marked] ; (ppo | rfe | ((prop \ id) & int)) ; [Marked]
100 acyclic hb as happens-before 100 acyclic hb as happens-before
101 101
102 (****************************************) 102 (****************************************)
103 (* Write and fence propagation ordering *) 103 (* Write and fence propagation ordering *)
104 (****************************************) 104 (****************************************)
105 105
106 (* Propagation: Each non-rf link needs a stron 106 (* Propagation: Each non-rf link needs a strong fence. *)
107 let pb = prop ; strong-fence ; hb* ; [Marked] 107 let pb = prop ; strong-fence ; hb* ; [Marked]
108 acyclic pb as propagation 108 acyclic pb as propagation
109 109
110 (*******) 110 (*******)
111 (* RCU *) 111 (* RCU *)
112 (*******) 112 (*******)
113 113
114 (* 114 (*
115 * Effects of read-side critical sections proc 115 * Effects of read-side critical sections proceed from the rcu_read_unlock()
116 * or srcu_read_unlock() backwards on the one 116 * or srcu_read_unlock() backwards on the one hand, and from the
117 * rcu_read_lock() or srcu_read_lock() forward 117 * rcu_read_lock() or srcu_read_lock() forwards on the other hand.
118 * 118 *
119 * In the definition of rcu-fence below, the p 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 ri 120 * of each disjunct and the po? term at the right-hand end have been factored
121 * out. They have been moved into the definit 121 * out. They have been moved into the definitions of rcu-link and rb.
122 * This was necessary in order to apply the "& 122 * This was necessary in order to apply the "& loc" tests correctly.
123 *) 123 *)
124 let rcu-gp = [Sync-rcu] (* Compare wit 124 let rcu-gp = [Sync-rcu] (* Compare with gp *)
125 let srcu-gp = [Sync-srcu] 125 let srcu-gp = [Sync-srcu]
126 let rcu-rscsi = rcu-rscs^-1 126 let rcu-rscsi = rcu-rscs^-1
127 let srcu-rscsi = srcu-rscs^-1 127 let srcu-rscsi = srcu-rscs^-1
128 128
129 (* 129 (*
130 * The synchronize_rcu() strong fence is speci 130 * The synchronize_rcu() strong fence is special in that it can order not
131 * one but two non-rf relations, but only in c 131 * one but two non-rf relations, but only in conjunction with an RCU
132 * read-side critical section. 132 * read-side critical section.
133 *) 133 *)
134 let rcu-link = po? ; hb* ; pb* ; prop ; po 134 let rcu-link = po? ; hb* ; pb* ; prop ; po
135 135
136 (* 136 (*
137 * Any sequence containing at least as many gr 137 * Any sequence containing at least as many grace periods as RCU read-side
138 * critical sections (joined by rcu-link) indu 138 * critical sections (joined by rcu-link) induces order like a generalized
139 * inter-CPU strong fence. 139 * inter-CPU strong fence.
140 * Likewise for SRCU grace periods and read-si 140 * Likewise for SRCU grace periods and read-side critical sections, provided
141 * the synchronize_srcu() and srcu_read_[un]lo 141 * the synchronize_srcu() and srcu_read_[un]lock() calls refer to the same
142 * struct srcu_struct location. 142 * struct srcu_struct location.
143 *) 143 *)
144 let rec rcu-order = rcu-gp | srcu-gp | 144 let rec rcu-order = rcu-gp | srcu-gp |
145 (rcu-gp ; rcu-link ; rcu-rscsi) | 145 (rcu-gp ; rcu-link ; rcu-rscsi) |
146 ((srcu-gp ; rcu-link ; srcu-rscsi) & l 146 ((srcu-gp ; rcu-link ; srcu-rscsi) & loc) |
147 (rcu-rscsi ; rcu-link ; rcu-gp) | 147 (rcu-rscsi ; rcu-link ; rcu-gp) |
148 ((srcu-rscsi ; rcu-link ; srcu-gp) & l 148 ((srcu-rscsi ; rcu-link ; srcu-gp) & loc) |
149 (rcu-gp ; rcu-link ; rcu-order ; rcu-l 149 (rcu-gp ; rcu-link ; rcu-order ; rcu-link ; rcu-rscsi) |
150 ((srcu-gp ; rcu-link ; rcu-order ; rcu 150 ((srcu-gp ; rcu-link ; rcu-order ; rcu-link ; srcu-rscsi) & loc) |
151 (rcu-rscsi ; rcu-link ; rcu-order ; rc 151 (rcu-rscsi ; rcu-link ; rcu-order ; rcu-link ; rcu-gp) |
152 ((srcu-rscsi ; rcu-link ; rcu-order ; 152 ((srcu-rscsi ; rcu-link ; rcu-order ; rcu-link ; srcu-gp) & loc) |
153 (rcu-order ; rcu-link ; rcu-order) 153 (rcu-order ; rcu-link ; rcu-order)
154 let rcu-fence = po ; rcu-order ; po? 154 let rcu-fence = po ; rcu-order ; po?
155 let fence = fence | rcu-fence 155 let fence = fence | rcu-fence
156 let strong-fence = strong-fence | rcu-fence 156 let strong-fence = strong-fence | rcu-fence
157 157
158 (* rb orders instructions just as pb does *) 158 (* rb orders instructions just as pb does *)
159 let rb = prop ; rcu-fence ; hb* ; pb* ; [Marke 159 let rb = prop ; rcu-fence ; hb* ; pb* ; [Marked]
160 160
161 irreflexive rb as rcu 161 irreflexive rb as rcu
162 162
163 (* 163 (*
164 * The happens-before, propagation, and rcu co 164 * The happens-before, propagation, and rcu constraints are all
165 * expressions of temporal ordering. They cou 165 * expressions of temporal ordering. They could be replaced by
166 * a single constraint on an "executes-before" 166 * a single constraint on an "executes-before" relation, xb:
167 * 167 *
168 * let xb = hb | pb | rb 168 * let xb = hb | pb | rb
169 * acyclic xb as executes-before 169 * acyclic xb as executes-before
170 *) 170 *)
171 171
172 (*********************************) 172 (*********************************)
173 (* Plain accesses and data races *) 173 (* Plain accesses and data races *)
174 (*********************************) 174 (*********************************)
175 175
176 (* Warn about plain writes and marked accesses 176 (* Warn about plain writes and marked accesses in the same region *)
177 let mixed-accesses = ([Plain & W] ; (po-loc \ 177 let mixed-accesses = ([Plain & W] ; (po-loc \ barrier) ; [Marked]) |
178 ([Marked] ; (po-loc \ barrier) ; [Plai 178 ([Marked] ; (po-loc \ barrier) ; [Plain & W])
179 flag ~empty mixed-accesses as mixed-accesses 179 flag ~empty mixed-accesses as mixed-accesses
180 180
181 (* Executes-before and visibility *) 181 (* Executes-before and visibility *)
182 let xbstar = (hb | pb | rb)* 182 let xbstar = (hb | pb | rb)*
183 let vis = cumul-fence* ; rfe? ; [Marked] ; 183 let vis = cumul-fence* ; rfe? ; [Marked] ;
184 ((strong-fence ; [Marked] ; xbstar) | 184 ((strong-fence ; [Marked] ; xbstar) | (xbstar & int))
185 185
186 (* Boundaries for lifetimes of plain accesses 186 (* Boundaries for lifetimes of plain accesses *)
187 let w-pre-bounded = [Marked] ; (addr | fence)? 187 let w-pre-bounded = [Marked] ; (addr | fence)?
188 let r-pre-bounded = [Marked] ; (addr | nonrw-f 188 let r-pre-bounded = [Marked] ; (addr | nonrw-fence |
189 ([R4rmb] ; fencerel(Rmb) ; [~Noreturn] 189 ([R4rmb] ; fencerel(Rmb) ; [~Noreturn]))?
190 let w-post-bounded = fence? ; [Marked] ; rmw-s 190 let w-post-bounded = fence? ; [Marked] ; rmw-sequence
191 let r-post-bounded = (nonrw-fence | ([~Noretur 191 let r-post-bounded = (nonrw-fence | ([~Noreturn] ; fencerel(Rmb) ; [R4rmb]))? ;
192 [Marked] 192 [Marked]
193 193
194 (* Visibility and executes-before for plain ac 194 (* Visibility and executes-before for plain accesses *)
195 let ww-vis = fence | (strong-fence ; xbstar ; 195 let ww-vis = fence | (strong-fence ; xbstar ; w-pre-bounded) |
196 (w-post-bounded ; vis ; w-pre-bounded) 196 (w-post-bounded ; vis ; w-pre-bounded)
197 let wr-vis = fence | (strong-fence ; xbstar ; 197 let wr-vis = fence | (strong-fence ; xbstar ; r-pre-bounded) |
198 (w-post-bounded ; vis ; r-pre-bounded) 198 (w-post-bounded ; vis ; r-pre-bounded)
199 let rw-xbstar = fence | (r-post-bounded ; xbst 199 let rw-xbstar = fence | (r-post-bounded ; xbstar ; w-pre-bounded)
200 200
201 (* Potential races *) 201 (* Potential races *)
202 let pre-race = ext & ((Plain * M) | ((M \ IW) 202 let pre-race = ext & ((Plain * M) | ((M \ IW) * Plain))
203 203
204 (* Coherence requirements for plain accesses * 204 (* Coherence requirements for plain accesses *)
205 let wr-incoh = pre-race & rf & rw-xbstar^-1 205 let wr-incoh = pre-race & rf & rw-xbstar^-1
206 let rw-incoh = pre-race & fr & wr-vis^-1 206 let rw-incoh = pre-race & fr & wr-vis^-1
207 let ww-incoh = pre-race & co & ww-vis^-1 207 let ww-incoh = pre-race & co & ww-vis^-1
208 empty (wr-incoh | rw-incoh | ww-incoh) as plai 208 empty (wr-incoh | rw-incoh | ww-incoh) as plain-coherence
209 209
210 (* Actual races *) 210 (* Actual races *)
211 let ww-nonrace = ww-vis & ((Marked * W) | rw-x 211 let ww-nonrace = ww-vis & ((Marked * W) | rw-xbstar) & ((W * Marked) | wr-vis)
212 let ww-race = (pre-race & co) \ ww-nonrace 212 let ww-race = (pre-race & co) \ ww-nonrace
213 let wr-race = (pre-race & (co? ; rf)) \ wr-vis 213 let wr-race = (pre-race & (co? ; rf)) \ wr-vis \ rw-xbstar^-1
214 let rw-race = (pre-race & fr) \ rw-xbstar 214 let rw-race = (pre-race & fr) \ rw-xbstar
215 215
216 flag ~empty (ww-race | wr-race | rw-race) as d 216 flag ~empty (ww-race | wr-race | rw-race) as data-race
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