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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 | * | |
1a00b455 | 8 | * An earlier version of this file appeared in the companion webpage for |
1c27b644 PM |
9 | * "Frightening small children and disconcerting grown-ups: Concurrency |
10 | * in the Linux kernel" by Alglave, Maranget, McKenney, Parri, and Stern, | |
1a00b455 | 11 | * which appeared in ASPLOS 2018. |
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12 | *) |
13 | ||
48d44d4e | 14 | "Linux-kernel memory consistency model" |
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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 | ||
21 | include "lock.cat" | |
22 | ||
23 | (*******************) | |
24 | (* Basic relations *) | |
25 | (*******************) | |
26 | ||
4494dd58 AS |
27 | (* Release Acquire *) |
28 | let acq-po = [Acquire] ; po ; [M] | |
29 | let po-rel = [M] ; po ; [Release] | |
ddfe1294 | 30 | let po-unlock-lock-po = po ; [UL] ; (po|rf) ; [LKR] ; po |
4494dd58 | 31 | |
1c27b644 | 32 | (* Fences *) |
4494dd58 AS |
33 | let R4rmb = R \ Noreturn (* Reads for which rmb works *) |
34 | let rmb = [R4rmb] ; fencerel(Rmb) ; [R4rmb] | |
1c27b644 PM |
35 | let wmb = [W] ; fencerel(Wmb) ; [W] |
36 | let mb = ([M] ; fencerel(Mb) ; [M]) | | |
cac79a39 PM |
37 | ([M] ; fencerel(Before-atomic) ; [RMW] ; po? ; [M]) | |
38 | ([M] ; po? ; [RMW] ; fencerel(After-atomic) ; [M]) | | |
5b735eb1 | 39 | ([M] ; po? ; [LKW] ; fencerel(After-spinlock) ; [M]) | |
dd409de2 JO |
40 | (* |
41 | * Note: The po-unlock-lock-po relation only passes the lock to the direct | |
42 | * successor, perhaps giving the impression that the ordering of the | |
43 | * smp_mb__after_unlock_lock() fence only affects a single lock handover. | |
44 | * However, in a longer sequence of lock handovers, the implicit | |
45 | * A-cumulative release fences of lock-release ensure that any stores that | |
46 | * propagate to one of the involved CPUs before it hands over the lock to | |
47 | * the next CPU will also propagate to the final CPU handing over the lock | |
48 | * to the CPU that executes the fence. Therefore, all those stores are | |
49 | * also affected by the fence. | |
50 | *) | |
51 | ([M] ; po-unlock-lock-po ; | |
02bae7a2 PM |
52 | [After-unlock-lock] ; po ; [M]) | |
53 | ([M] ; po? ; [Srcu-unlock] ; fencerel(After-srcu-read-unlock) ; [M]) | |
a3f600d9 | 54 | let gp = po ; [Sync-rcu | Sync-srcu] ; po? |
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55 | let strong-fence = mb | gp |
56 | ||
4494dd58 AS |
57 | let nonrw-fence = strong-fence | po-rel | acq-po |
58 | let fence = nonrw-fence | wmb | rmb | |
0031e38a | 59 | let barrier = fencerel(Barrier | Rmb | Wmb | Mb | Sync-rcu | Sync-srcu | |
f9de4171 AS |
60 | Before-atomic | After-atomic | Acquire | Release | |
61 | Rcu-lock | Rcu-unlock | Srcu-lock | Srcu-unlock) | | |
0031e38a | 62 | (po ; [Release]) | ([Acquire] ; po) |
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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 | |
0031e38a | 83 | let to-w = rwdep | (overwrite & int) | (addr ; [Plain] ; wmb) |
aa568c26 | 84 | let to-r = (addr ; [R]) | (dep ; [Marked] ; rfi) |
762e9357 | 85 | let ppo = to-r | to-w | (fence & int) | (po-unlock-lock-po & int) |
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86 | |
87 | (* Propagation: Ordering from release operations and strong fences. *) | |
d1a84ab1 | 88 | let A-cumul(r) = (rfe ; [Marked])? ; r |
ebd50e29 | 89 | let rmw-sequence = (rf ; rmw)* |
d1a84ab1 | 90 | let cumul-fence = [Marked] ; (A-cumul(strong-fence | po-rel) | wmb | |
ebd50e29 | 91 | po-unlock-lock-po) ; [Marked] ; rmw-sequence |
d1a84ab1 AS |
92 | let prop = [Marked] ; (overwrite & ext)? ; cumul-fence* ; |
93 | [Marked] ; rfe? ; [Marked] | |
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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 | *) | |
d1a84ab1 | 99 | let hb = [Marked] ; (ppo | rfe | ((prop \ id) & int)) ; [Marked] |
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100 | acyclic hb as happens-before |
101 | ||
102 | (****************************************) | |
103 | (* Write and fence propagation ordering *) | |
104 | (****************************************) | |
105 | ||
106 | (* Propagation: Each non-rf link needs a strong fence. *) | |
d1a84ab1 | 107 | let pb = prop ; strong-fence ; hb* ; [Marked] |
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108 | acyclic pb as propagation |
109 | ||
110 | (*******) | |
111 | (* RCU *) | |
112 | (*******) | |
113 | ||
114 | (* | |
284749b0 | 115 | * Effects of read-side critical sections proceed from the rcu_read_unlock() |
a3f600d9 AS |
116 | * or srcu_read_unlock() backwards on the one hand, and from the |
117 | * rcu_read_lock() or srcu_read_lock() forwards on the other hand. | |
284749b0 AS |
118 | * |
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 right-hand end have been factored | |
121 | * out. They have been moved into the definitions of rcu-link and rb. | |
a3f600d9 | 122 | * This was necessary in order to apply the "& loc" tests correctly. |
1c27b644 | 123 | *) |
284749b0 | 124 | let rcu-gp = [Sync-rcu] (* Compare with gp *) |
a3f600d9 | 125 | let srcu-gp = [Sync-srcu] |
284749b0 | 126 | let rcu-rscsi = rcu-rscs^-1 |
a3f600d9 | 127 | let srcu-rscsi = srcu-rscs^-1 |
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128 | |
129 | (* | |
130 | * The synchronize_rcu() strong fence is special in that it can order not | |
131 | * one but two non-rf relations, but only in conjunction with an RCU | |
132 | * read-side critical section. | |
133 | *) | |
284749b0 | 134 | let rcu-link = po? ; hb* ; pb* ; prop ; po |
1c27b644 | 135 | |
1c27b644 | 136 | (* |
9d036883 | 137 | * Any sequence containing at least as many grace periods as RCU read-side |
15aa25cb AS |
138 | * critical sections (joined by rcu-link) induces order like a generalized |
139 | * inter-CPU strong fence. | |
a3f600d9 AS |
140 | * Likewise for SRCU grace periods and read-side critical sections, provided |
141 | * the synchronize_srcu() and srcu_read_[un]lock() calls refer to the same | |
142 | * struct srcu_struct location. | |
1c27b644 | 143 | *) |
15aa25cb | 144 | let rec rcu-order = rcu-gp | srcu-gp | |
284749b0 | 145 | (rcu-gp ; rcu-link ; rcu-rscsi) | |
a3f600d9 | 146 | ((srcu-gp ; rcu-link ; srcu-rscsi) & loc) | |
284749b0 | 147 | (rcu-rscsi ; rcu-link ; rcu-gp) | |
a3f600d9 | 148 | ((srcu-rscsi ; rcu-link ; srcu-gp) & loc) | |
15aa25cb AS |
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) | |
154 | let rcu-fence = po ; rcu-order ; po? | |
155 | let fence = fence | rcu-fence | |
156 | let strong-fence = strong-fence | rcu-fence | |
9d036883 AS |
157 | |
158 | (* rb orders instructions just as pb does *) | |
15aa25cb | 159 | let rb = prop ; rcu-fence ; hb* ; pb* ; [Marked] |
1c27b644 | 160 | |
1ee2da5f | 161 | irreflexive rb as rcu |
9d036883 AS |
162 | |
163 | (* | |
164 | * The happens-before, propagation, and rcu constraints are all | |
165 | * expressions of temporal ordering. They could be replaced by | |
166 | * a single constraint on an "executes-before" relation, xb: | |
167 | * | |
168 | * let xb = hb | pb | rb | |
169 | * acyclic xb as executes-before | |
170 | *) | |
0031e38a AS |
171 | |
172 | (*********************************) | |
173 | (* Plain accesses and data races *) | |
174 | (*********************************) | |
175 | ||
176 | (* Warn about plain writes and marked accesses in the same region *) | |
177 | let mixed-accesses = ([Plain & W] ; (po-loc \ barrier) ; [Marked]) | | |
178 | ([Marked] ; (po-loc \ barrier) ; [Plain & W]) | |
179 | flag ~empty mixed-accesses as mixed-accesses | |
180 | ||
181 | (* Executes-before and visibility *) | |
182 | let xbstar = (hb | pb | rb)* | |
0031e38a | 183 | let vis = cumul-fence* ; rfe? ; [Marked] ; |
15aa25cb | 184 | ((strong-fence ; [Marked] ; xbstar) | (xbstar & int)) |
0031e38a AS |
185 | |
186 | (* Boundaries for lifetimes of plain accesses *) | |
187 | let w-pre-bounded = [Marked] ; (addr | fence)? | |
188 | let r-pre-bounded = [Marked] ; (addr | nonrw-fence | | |
189 | ([R4rmb] ; fencerel(Rmb) ; [~Noreturn]))? | |
ebd50e29 | 190 | let w-post-bounded = fence? ; [Marked] ; rmw-sequence |
0031e38a AS |
191 | let r-post-bounded = (nonrw-fence | ([~Noreturn] ; fencerel(Rmb) ; [R4rmb]))? ; |
192 | [Marked] | |
193 | ||
194 | (* Visibility and executes-before for plain accesses *) | |
4289ee7d AS |
195 | let ww-vis = fence | (strong-fence ; xbstar ; w-pre-bounded) | |
196 | (w-post-bounded ; vis ; w-pre-bounded) | |
197 | let wr-vis = fence | (strong-fence ; xbstar ; r-pre-bounded) | | |
198 | (w-post-bounded ; vis ; r-pre-bounded) | |
199 | let rw-xbstar = fence | (r-post-bounded ; xbstar ; w-pre-bounded) | |
0031e38a AS |
200 | |
201 | (* Potential races *) | |
202 | let pre-race = ext & ((Plain * M) | ((M \ IW) * Plain)) | |
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 plain-coherence | |
209 | ||
210 | (* Actual races *) | |
211 | let ww-nonrace = ww-vis & ((Marked * W) | rw-xbstar) & ((W * Marked) | wr-vis) | |
212 | let ww-race = (pre-race & co) \ ww-nonrace | |
daebf24a | 213 | let wr-race = (pre-race & (co? ; rf)) \ wr-vis \ rw-xbstar^-1 |
0031e38a AS |
214 | let rw-race = (pre-race & fr) \ rw-xbstar |
215 | ||
216 | flag ~empty (ww-race | wr-race | rw-race) as data-race |