1 // SPDX-License-Identifier: GPL-2.0+
3 * Copyright (C) 2016 Luc Maranget <luc.maranget@inria.fr> for Inria
4 * Copyright (C) 2017 Alan Stern <stern@rowland.harvard.edu>
8 * Generate coherence orders and handle lock operations
10 * Warning: spin_is_locked() crashes herd7 versions strictly before 7.48.
11 * spin_is_locked() is functional from herd7 version 7.49.
17 * The lock-related events generated by herd are as follows:
19 * LKR Lock-Read: the read part of a spin_lock() or successful
20 * spin_trylock() read-modify-write event pair
21 * LKW Lock-Write: the write part of a spin_lock() or successful
22 * spin_trylock() RMW event pair
23 * UL Unlock: a spin_unlock() event
24 * LF Lock-Fail: a failed spin_trylock() event
25 * RL Read-Locked: a spin_is_locked() event which returns True
26 * RU Read-Unlocked: a spin_is_locked() event which returns False
28 * LKR and LKW events always come paired, like all RMW event sequences.
30 * LKR, LF, RL, and RU are read events; LKR has Acquire ordering.
31 * LKW and UL are write events; UL has Release ordering.
32 * LKW, LF, RL, and RU have no ordering properties.
35 (* Link Lock-Reads to their RMW-partner Lock-Writes *)
36 let lk-rmw = ([LKR] ; po-loc ; [LKW]) \ (po ; po)
37 let rmw = rmw | lk-rmw
40 * A paired LKR must always see an unlocked value; spin_lock() calls nested
41 * inside a critical section (for the same lock) always deadlock.
43 empty ([LKW] ; po-loc ; [domain(lk-rmw)]) \ (po-loc ; [UL] ; po-loc)
46 (* The litmus test is invalid if an LKW event is not part of an RMW pair *)
47 flag ~empty LKW \ range(lk-rmw) as unpaired-LKW
49 (* This will be allowed if we implement spin_is_locked() *)
50 flag ~empty LKR \ domain(lk-rmw) as unpaired-LKR
52 (* There should be no ordinary R or W accesses to spinlocks *)
53 let ALL-LOCKS = LKR | LKW | UL | LF
54 flag ~empty [M \ IW] ; loc ; [ALL-LOCKS] as mixed-lock-accesses
56 (* The final value of a spinlock should not be tested *)
57 flag ~empty [FW] ; loc ; [ALL-LOCKS] as lock-final
59 (* Backward compatibility *)
60 let RL = try RL with emptyset
61 let RU = try RU with emptyset
63 (* Treat RL as a kind of LF: a read with no ordering properties *)
67 * Put lock operations in their appropriate classes, but leave UL out of W
68 * until after the co relation has been generated.
70 let R = R | LKR | LF | RU
73 let Release = Release | UL
74 let Acquire = Acquire | LKR
76 (* Match LKW events to their corresponding UL events *)
77 let critical = ([LKW] ; po-loc ; [UL]) \ (po-loc ; [LKW | UL] ; po-loc)
79 flag ~empty UL \ range(critical) as unmatched-unlock
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
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)
88 (* rfe for LF events *)
89 let all-possible-rfe-lf =
91 * Given an LF event r, compute the possible rfe edges for that event
92 * (all those starting from LKW events in other threads),
93 * and then convert that relation to a set of single-edge relations.
95 let possible-rfe-lf r =
96 let pair-to-relation p = p ++ 0
97 in map pair-to-relation ((LKW * {r}) & loc & ext)
98 (* Do this for each LF event r that isn't in rfi-lf *)
99 in map possible-rfe-lf (LF \ range(rfi-lf))
101 (* Generate all rf relations for LF events *)
102 with rfe-lf from cross(all-possible-rfe-lf)
103 let rf-lf = rfe-lf | rfi-lf
106 * RU, i.e., spin_is_locked() returning False, is slightly different.
107 * We rely on the memory model to rule out cases where spin_is_locked()
108 * within one of the lock's critical sections returns False.
111 (* rfi for RU events: an RU may read from the last po-previous UL *)
112 let rfi-ru = ([UL] ; po-loc ; [RU]) \ ([UL] ; po-loc ; [LKW] ; po-loc)
114 (* rfe for RU events: an RU may read from an external UL or the initial write *)
115 let all-possible-rfe-ru =
116 let possible-rfe-ru r =
117 let pair-to-relation p = p ++ 0
118 in map pair-to-relation (((UL|IW) * {r}) & loc & ext)
119 in map possible-rfe-ru RU
121 (* Generate all rf relations for RU events *)
122 with rfe-ru from cross(all-possible-rfe-ru)
123 let rf-ru = rfe-ru | rfi-ru
125 (* Final rf relation *)
126 let rf = rf | rf-lf | rf-ru
128 (* Generate all co relations, including LKW events but not UL *)
129 let co0 = co0 | ([IW] ; loc ; [LKW]) |
130 (([LKW] ; loc ; [UNMATCHED-LKW]) \ [UNMATCHED-LKW])
131 include "cos-opt.cat"
135 (* Merge UL events into co *)
136 let co = (co | critical | (critical^-1 ; co))+
140 (* Merge LKR events into rf *)
141 let rf = rf | ([IW | UL] ; singlestep(co) ; lk-rmw^-1)