1 // SPDX-License-Identifier: GPL-2.0+
2 (*
3 * Copyright (C) 2016 Luc Maranget <luc.maranget@inria.fr> for Inria
4 * Copyright (C) 2017 Alan Stern <stern@rowland.harvard.edu>
5 *)
6
7 (*
8 * Generate coherence orders and handle lock operations
9 *)
10
11 include "cross.cat"
12
13 (*
14 * The lock-related events generated by herd7 are as follows:
15 *
16 * LKR Lock-Read: the read part of a spin_lock() or successful
17 * spin_trylock() read-modify-write event pair
18 * LKW Lock-Write: the write part of a spin_lock() or successful
19 * spin_trylock() RMW event pair
20 * UL Unlock: a spin_unlock() event
21 * LF Lock-Fail: a failed spin_trylock() event
22 * RL Read-Locked: a spin_is_locked() event which returns True
23 * RU Read-Unlocked: a spin_is_locked() event which returns False
24 *
25 * LKR and LKW events always come paired, like all RMW event sequences.
26 *
27 * LKR, LF, RL, and RU are read events; LKR has Acquire ordering.
28 * LKW and UL are write events; UL has Release ordering.
29 * LKW, LF, RL, and RU have no ordering properties.
30 *)
31
32 (* Backward compatibility *)
33 let RL = try RL with emptyset
34 let RU = try RU with emptyset
35
36 (* Treat RL as a kind of LF: a read with no ordering properties *)
37 let LF = LF | RL
38
39 (* There should be no ordinary R or W accesses to spinlocks or SRCU structs *)
40 let ALL-LOCKS = LKR | LKW | UL | LF | RU | Srcu-lock | Srcu-unlock | Sync-srcu
41 flag ~empty [M \ IW \ ALL-LOCKS] ; loc ; [ALL-LOCKS] as mixed-lock-accesses
42
43 (* Link Lock-Reads to their RMW-partner Lock-Writes *)
44 let lk-rmw = ([LKR] ; po-loc ; [LKW]) \ (po ; po)
45 let rmw = rmw | lk-rmw
46
47 (* The litmus test is invalid if an LKR/LKW event is not part of an RMW pair *)
48 flag ~empty LKW \ range(lk-rmw) as unpaired-LKW
49 flag ~empty LKR \ domain(lk-rmw) as unpaired-LKR
50
51 (*
52 * An LKR must always see an unlocked value; spin_lock() calls nested
53 * inside a critical section (for the same lock) always deadlock.
54 *)
55 empty ([LKW] ; po-loc ; [LKR]) \ (po-loc ; [UL] ; po-loc) as lock-nest
56
57 (*
58 * In the same way, spin_is_locked() inside a critical section must always
59 * return True (no RU events can be in a critical section for the same lock).
60 *)
61 empty ([LKW] ; po-loc ; [RU]) \ (po-loc ; [UL] ; po-loc) as nested-is-locked
62
63 (* The final value of a spinlock should not be tested *)
64 flag ~empty [FW] ; loc ; [ALL-LOCKS] as lock-final
65
66 (*
67 * Put lock operations in their appropriate classes, but leave UL out of W
68 * until after the co relation has been generated.
69 *)
70 let R = R | LKR | LF | RU
71 let W = W | LKW
72
73 let Release = Release | UL
74 let Acquire = Acquire | LKR
75
76 (* Match LKW events to their corresponding UL events *)
77 let critical = ([LKW] ; po-loc ; [UL]) \ (po-loc ; [LKW | UL] ; po-loc)
78
79 flag ~empty UL \ range(critical) as unmatched-unlock
80
81 (* Allow up to one unmatched LKW per location; more must deadlock *)
82 let UNMATCHED-LKW = LKW \ domain(critical)
83 empty ([UNMATCHED-LKW] ; loc ; [UNMATCHED-LKW]) \ id as unmatched-locks
84
85 (* rfi for LF events: link each LKW to the LF events in its critical section *)
86 let rfi-lf = ([LKW] ; po-loc ; [LF]) \ ([LKW] ; po-loc ; [UL] ; po-loc)
87
88 (* Utility macro to convert a single pair to a single-edge relation *)
89 let pair-to-relation p = p ++ 0
90
91 (*
92 * If a given LF event e is outside a critical section, it cannot read
93 * internally but it may read from an LKW event in another thread.
94 * Compute the relation containing these possible edges.
95 *)
96 let possible-rfe-noncrit-lf e = (LKW * {e}) & loc & ext
97
98 (* Compute set of sets of possible rfe edges for LF events *)
99 let all-possible-rfe-lf =
100 (*
101 * Convert the possible-rfe-noncrit-lf relation for e
102 * to a set of single edges
103 *)
104 let set-of-singleton-rfe-lf e =
105 map pair-to-relation (possible-rfe-noncrit-lf e)
106 (* Do this for each LF event e that isn't in rfi-lf *)
107 in map set-of-singleton-rfe-lf (LF \ range(rfi-lf))
108
109 (* Generate all rf relations for LF events *)
110 with rfe-lf from cross(all-possible-rfe-lf)
111 let rf-lf = rfe-lf | rfi-lf
112
113 (*
114 * A given RU event e may read internally from the last po-previous UL,
115 * or it may read from a UL event in another thread or the initial write.
116 * Compute the relation containing these possible edges.
117 *)
118 let possible-rf-ru e = (((UL * {e}) & po-loc) \
119 ([UL] ; po-loc ; [UL] ; po-loc)) |
120 (((UL | IW) * {e}) & loc & ext)
121
122 (* Compute set of sets of possible rf edges for RU events *)
123 let all-possible-rf-ru =
124 (* Convert the possible-rf-ru relation for e to a set of single edges *)
125 let set-of-singleton-rf-ru e =
126 map pair-to-relation (possible-rf-ru e)
127 (* Do this for each RU event e *)
128 in map set-of-singleton-rf-ru RU
129
130 (* Generate all rf relations for RU events *)
131 with rf-ru from cross(all-possible-rf-ru)
132
133 (* Final rf relation *)
134 let rf = rf | rf-lf | rf-ru
135
136 (* Generate all co relations, including LKW events but not UL *)
137 let co0 = co0 | ([IW] ; loc ; [LKW]) |
138 (([LKW] ; loc ; [UNMATCHED-LKW]) \ [UNMATCHED-LKW])
139 include "cos-opt.cat"
140 let W = W | UL
141 let M = R | W
142
143 (* Merge UL events into co *)
144 let co = (co | critical | (critical^-1 ; co))+
145 let coe = co & ext
146 let coi = co & int
147
148 (* Merge LKR events into rf *)
149 let rf = rf | ([IW | UL] ; singlestep(co) ; lk-rmw^-1)
150 let rfe = rf & ext
151 let rfi = rf & int
152
153 let fr = rf^-1 ; co
154 let fre = fr & ext
155 let fri = fr & int
156
157 show co,rf,fr
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