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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 | * | |
8 | * An earlier version of this file appears 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 is to appear in ASPLOS 2018. | |
12 | *) | |
13 | ||
48d44d4e | 14 | "Linux-kernel memory consistency model" |
1c27b644 PM |
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 | ||
27 | (* Fences *) | |
1c27b644 PM |
28 | let rmb = [R \ Noreturn] ; fencerel(Rmb) ; [R \ Noreturn] |
29 | let wmb = [W] ; fencerel(Wmb) ; [W] | |
30 | let mb = ([M] ; fencerel(Mb) ; [M]) | | |
cac79a39 PM |
31 | ([M] ; fencerel(Before-atomic) ; [RMW] ; po? ; [M]) | |
32 | ([M] ; po? ; [RMW] ; fencerel(After-atomic) ; [M]) | | |
33 | ([M] ; po? ; [LKW] ; fencerel(After-spinlock) ; [M]) | |
1c27b644 PM |
34 | let gp = po ; [Sync-rcu] ; po? |
35 | ||
36 | let strong-fence = mb | gp | |
37 | ||
38 | (* Release Acquire *) | |
39 | let acq-po = [Acquire] ; po ; [M] | |
40 | let po-rel = [M] ; po ; [Release] | |
41 | let rfi-rel-acq = [Release] ; rfi ; [Acquire] | |
42 | ||
43 | (**********************************) | |
44 | (* Fundamental coherence ordering *) | |
45 | (**********************************) | |
46 | ||
47 | (* Sequential Consistency Per Variable *) | |
48 | let com = rf | co | fr | |
49 | acyclic po-loc | com as coherence | |
50 | ||
51 | (* Atomic Read-Modify-Write *) | |
52 | empty rmw & (fre ; coe) as atomic | |
53 | ||
54 | (**********************************) | |
55 | (* Instruction execution ordering *) | |
56 | (**********************************) | |
57 | ||
58 | (* Preserved Program Order *) | |
59 | let dep = addr | data | |
60 | let rwdep = (dep | ctrl) ; [W] | |
61 | let overwrite = co | fr | |
62 | let to-w = rwdep | (overwrite & int) | |
bf28ae56 | 63 | let to-r = addr | (dep ; rfi) | rfi-rel-acq |
1c27b644 | 64 | let fence = strong-fence | wmb | po-rel | rmb | acq-po |
bf28ae56 | 65 | let ppo = to-r | to-w | fence |
1c27b644 PM |
66 | |
67 | (* Propagation: Ordering from release operations and strong fences. *) | |
68 | let A-cumul(r) = rfe? ; r | |
69 | let cumul-fence = A-cumul(strong-fence | po-rel) | wmb | |
70 | let prop = (overwrite & ext)? ; cumul-fence* ; rfe? | |
71 | ||
72 | (* | |
73 | * Happens Before: Ordering from the passage of time. | |
74 | * No fences needed here for prop because relation confined to one process. | |
75 | *) | |
76 | let hb = ppo | rfe | ((prop \ id) & int) | |
77 | acyclic hb as happens-before | |
78 | ||
79 | (****************************************) | |
80 | (* Write and fence propagation ordering *) | |
81 | (****************************************) | |
82 | ||
83 | (* Propagation: Each non-rf link needs a strong fence. *) | |
84 | let pb = prop ; strong-fence ; hb* | |
85 | acyclic pb as propagation | |
86 | ||
87 | (*******) | |
88 | (* RCU *) | |
89 | (*******) | |
90 | ||
91 | (* | |
92 | * Effect of read-side critical section proceeds from the rcu_read_lock() | |
93 | * onward on the one hand and from the rcu_read_unlock() backwards on the | |
94 | * other hand. | |
95 | *) | |
96 | let rscs = po ; crit^-1 ; po? | |
97 | ||
98 | (* | |
99 | * The synchronize_rcu() strong fence is special in that it can order not | |
100 | * one but two non-rf relations, but only in conjunction with an RCU | |
101 | * read-side critical section. | |
102 | *) | |
103 | let link = hb* ; pb* ; prop | |
104 | ||
105 | (* Chains that affect the RCU grace-period guarantee *) | |
106 | let gp-link = gp ; link | |
107 | let rscs-link = rscs ; link | |
108 | ||
109 | (* | |
110 | * A cycle containing at least as many grace periods as RCU read-side | |
111 | * critical sections is forbidden. | |
112 | *) | |
113 | let rec rcu-path = | |
114 | gp-link | | |
115 | (gp-link ; rscs-link) | | |
116 | (rscs-link ; gp-link) | | |
117 | (rcu-path ; rcu-path) | | |
118 | (gp-link ; rcu-path ; rscs-link) | | |
119 | (rscs-link ; rcu-path ; gp-link) | |
120 | ||
121 | irreflexive rcu-path as rcu |