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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 |
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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] | |
30 | let po-unlock-rf-lock-po = po ; [UL] ; rf ; [LKR] ; po | |
31 | ||
1c27b644 | 32 | (* Fences *) |
4494dd58 AS |
33 | let R4rmb = R \ Noreturn (* Reads for which rmb works *) |
34 | let rmb = [R4rmb] ; fencerel(Rmb) ; [R4rmb] | |
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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 AP |
39 | ([M] ; po? ; [LKW] ; fencerel(After-spinlock) ; [M]) | |
40 | ([M] ; po ; [UL] ; (co | po) ; [LKW] ; | |
41 | fencerel(After-unlock-lock) ; [M]) | |
a3f600d9 | 42 | let gp = po ; [Sync-rcu | Sync-srcu] ; po? |
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43 | let strong-fence = mb | gp |
44 | ||
4494dd58 AS |
45 | let nonrw-fence = strong-fence | po-rel | acq-po |
46 | let fence = nonrw-fence | wmb | rmb | |
0031e38a AS |
47 | let barrier = fencerel(Barrier | Rmb | Wmb | Mb | Sync-rcu | Sync-srcu | |
48 | Before-atomic | After-atomic | Acquire | Release) | | |
49 | (po ; [Release]) | ([Acquire] ; po) | |
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50 | |
51 | (**********************************) | |
52 | (* Fundamental coherence ordering *) | |
53 | (**********************************) | |
54 | ||
55 | (* Sequential Consistency Per Variable *) | |
56 | let com = rf | co | fr | |
57 | acyclic po-loc | com as coherence | |
58 | ||
59 | (* Atomic Read-Modify-Write *) | |
60 | empty rmw & (fre ; coe) as atomic | |
61 | ||
62 | (**********************************) | |
63 | (* Instruction execution ordering *) | |
64 | (**********************************) | |
65 | ||
66 | (* Preserved Program Order *) | |
67 | let dep = addr | data | |
68 | let rwdep = (dep | ctrl) ; [W] | |
69 | let overwrite = co | fr | |
0031e38a | 70 | let to-w = rwdep | (overwrite & int) | (addr ; [Plain] ; wmb) |
d1a84ab1 | 71 | let to-r = addr | (dep ; [Marked] ; rfi) |
6e89e831 | 72 | let ppo = to-r | to-w | fence | (po-unlock-rf-lock-po & int) |
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73 | |
74 | (* Propagation: Ordering from release operations and strong fences. *) | |
d1a84ab1 AS |
75 | let A-cumul(r) = (rfe ; [Marked])? ; r |
76 | let cumul-fence = [Marked] ; (A-cumul(strong-fence | po-rel) | wmb | | |
77 | po-unlock-rf-lock-po) ; [Marked] | |
78 | let prop = [Marked] ; (overwrite & ext)? ; cumul-fence* ; | |
79 | [Marked] ; rfe? ; [Marked] | |
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80 | |
81 | (* | |
82 | * Happens Before: Ordering from the passage of time. | |
83 | * No fences needed here for prop because relation confined to one process. | |
84 | *) | |
d1a84ab1 | 85 | let hb = [Marked] ; (ppo | rfe | ((prop \ id) & int)) ; [Marked] |
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86 | acyclic hb as happens-before |
87 | ||
88 | (****************************************) | |
89 | (* Write and fence propagation ordering *) | |
90 | (****************************************) | |
91 | ||
92 | (* Propagation: Each non-rf link needs a strong fence. *) | |
d1a84ab1 | 93 | let pb = prop ; strong-fence ; hb* ; [Marked] |
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94 | acyclic pb as propagation |
95 | ||
96 | (*******) | |
97 | (* RCU *) | |
98 | (*******) | |
99 | ||
100 | (* | |
284749b0 | 101 | * Effects of read-side critical sections proceed from the rcu_read_unlock() |
a3f600d9 AS |
102 | * or srcu_read_unlock() backwards on the one hand, and from the |
103 | * rcu_read_lock() or srcu_read_lock() forwards on the other hand. | |
284749b0 AS |
104 | * |
105 | * In the definition of rcu-fence below, the po term at the left-hand side | |
106 | * of each disjunct and the po? term at the right-hand end have been factored | |
107 | * out. They have been moved into the definitions of rcu-link and rb. | |
a3f600d9 | 108 | * This was necessary in order to apply the "& loc" tests correctly. |
1c27b644 | 109 | *) |
284749b0 | 110 | let rcu-gp = [Sync-rcu] (* Compare with gp *) |
a3f600d9 | 111 | let srcu-gp = [Sync-srcu] |
284749b0 | 112 | let rcu-rscsi = rcu-rscs^-1 |
a3f600d9 | 113 | let srcu-rscsi = srcu-rscs^-1 |
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114 | |
115 | (* | |
116 | * The synchronize_rcu() strong fence is special in that it can order not | |
117 | * one but two non-rf relations, but only in conjunction with an RCU | |
118 | * read-side critical section. | |
119 | *) | |
284749b0 | 120 | let rcu-link = po? ; hb* ; pb* ; prop ; po |
1c27b644 | 121 | |
1c27b644 | 122 | (* |
9d036883 AS |
123 | * Any sequence containing at least as many grace periods as RCU read-side |
124 | * critical sections (joined by rcu-link) acts as a generalized strong fence. | |
a3f600d9 AS |
125 | * Likewise for SRCU grace periods and read-side critical sections, provided |
126 | * the synchronize_srcu() and srcu_read_[un]lock() calls refer to the same | |
127 | * struct srcu_struct location. | |
1c27b644 | 128 | *) |
a3f600d9 | 129 | let rec rcu-fence = rcu-gp | srcu-gp | |
284749b0 | 130 | (rcu-gp ; rcu-link ; rcu-rscsi) | |
a3f600d9 | 131 | ((srcu-gp ; rcu-link ; srcu-rscsi) & loc) | |
284749b0 | 132 | (rcu-rscsi ; rcu-link ; rcu-gp) | |
a3f600d9 | 133 | ((srcu-rscsi ; rcu-link ; srcu-gp) & loc) | |
284749b0 | 134 | (rcu-gp ; rcu-link ; rcu-fence ; rcu-link ; rcu-rscsi) | |
a3f600d9 | 135 | ((srcu-gp ; rcu-link ; rcu-fence ; rcu-link ; srcu-rscsi) & loc) | |
284749b0 | 136 | (rcu-rscsi ; rcu-link ; rcu-fence ; rcu-link ; rcu-gp) | |
a3f600d9 | 137 | ((srcu-rscsi ; rcu-link ; rcu-fence ; rcu-link ; srcu-gp) & loc) | |
9d036883 AS |
138 | (rcu-fence ; rcu-link ; rcu-fence) |
139 | ||
140 | (* rb orders instructions just as pb does *) | |
d1a84ab1 | 141 | let rb = prop ; po ; rcu-fence ; po? ; hb* ; pb* ; [Marked] |
1c27b644 | 142 | |
1ee2da5f | 143 | irreflexive rb as rcu |
9d036883 AS |
144 | |
145 | (* | |
146 | * The happens-before, propagation, and rcu constraints are all | |
147 | * expressions of temporal ordering. They could be replaced by | |
148 | * a single constraint on an "executes-before" relation, xb: | |
149 | * | |
150 | * let xb = hb | pb | rb | |
151 | * acyclic xb as executes-before | |
152 | *) | |
0031e38a AS |
153 | |
154 | (*********************************) | |
155 | (* Plain accesses and data races *) | |
156 | (*********************************) | |
157 | ||
158 | (* Warn about plain writes and marked accesses in the same region *) | |
159 | let mixed-accesses = ([Plain & W] ; (po-loc \ barrier) ; [Marked]) | | |
160 | ([Marked] ; (po-loc \ barrier) ; [Plain & W]) | |
161 | flag ~empty mixed-accesses as mixed-accesses | |
162 | ||
163 | (* Executes-before and visibility *) | |
164 | let xbstar = (hb | pb | rb)* | |
165 | let full-fence = strong-fence | (po ; rcu-fence ; po?) | |
166 | let vis = cumul-fence* ; rfe? ; [Marked] ; | |
167 | ((full-fence ; [Marked] ; xbstar) | (xbstar & int)) | |
168 | ||
169 | (* Boundaries for lifetimes of plain accesses *) | |
170 | let w-pre-bounded = [Marked] ; (addr | fence)? | |
171 | let r-pre-bounded = [Marked] ; (addr | nonrw-fence | | |
172 | ([R4rmb] ; fencerel(Rmb) ; [~Noreturn]))? | |
173 | let w-post-bounded = fence? ; [Marked] | |
174 | let r-post-bounded = (nonrw-fence | ([~Noreturn] ; fencerel(Rmb) ; [R4rmb]))? ; | |
175 | [Marked] | |
176 | ||
177 | (* Visibility and executes-before for plain accesses *) | |
178 | let ww-vis = w-post-bounded ; vis ; w-pre-bounded | |
179 | let wr-vis = w-post-bounded ; vis ; r-pre-bounded | |
180 | let rw-xbstar = r-post-bounded ; xbstar ; w-pre-bounded | |
181 | ||
182 | (* Potential races *) | |
183 | let pre-race = ext & ((Plain * M) | ((M \ IW) * Plain)) | |
184 | ||
185 | (* Coherence requirements for plain accesses *) | |
186 | let wr-incoh = pre-race & rf & rw-xbstar^-1 | |
187 | let rw-incoh = pre-race & fr & wr-vis^-1 | |
188 | let ww-incoh = pre-race & co & ww-vis^-1 | |
189 | empty (wr-incoh | rw-incoh | ww-incoh) as plain-coherence | |
190 | ||
191 | (* Actual races *) | |
192 | let ww-nonrace = ww-vis & ((Marked * W) | rw-xbstar) & ((W * Marked) | wr-vis) | |
193 | let ww-race = (pre-race & co) \ ww-nonrace | |
194 | let wr-race = (pre-race & (co? ; rf)) \ wr-vis | |
195 | let rw-race = (pre-race & fr) \ rw-xbstar | |
196 | ||
197 | flag ~empty (ww-race | wr-race | rw-race) as data-race |