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 * Warning: spin_is_locked() crashes herd7 versions strictly before 7.48. 11 * spin_is_locked() is functional from herd7 version 7.49. 12 *) 13 14include "cross.cat" 15 16(* 17 * The lock-related events generated by herd are as follows: 18 * 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 27 * 28 * LKR and LKW events always come paired, like all RMW event sequences. 29 * 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. 33 *) 34 35(* Backward compatibility *) 36let RL = try RL with emptyset 37let RU = try RU with emptyset 38 39(* Treat RL as a kind of LF: a read with no ordering properties *) 40let LF = LF | RL 41 42(* There should be no ordinary R or W accesses to spinlocks *) 43let ALL-LOCKS = LKR | LKW | UL | LF | RU 44flag ~empty [M \ IW] ; loc ; [ALL-LOCKS] as mixed-lock-accesses 45 46(* Link Lock-Reads to their RMW-partner Lock-Writes *) 47let lk-rmw = ([LKR] ; po-loc ; [LKW]) \ (po ; po) 48let rmw = rmw | lk-rmw 49 50(* The litmus test is invalid if an LKR/LKW event is not part of an RMW pair *) 51flag ~empty LKW \ range(lk-rmw) as unpaired-LKW 52flag ~empty LKR \ domain(lk-rmw) as unpaired-LKR 53 54(* 55 * An LKR must always see an unlocked value; spin_lock() calls nested 56 * inside a critical section (for the same lock) always deadlock. 57 *) 58empty ([LKW] ; po-loc ; [LKR]) \ (po-loc ; [UL] ; po-loc) as lock-nest 59 60(* The final value of a spinlock should not be tested *) 61flag ~empty [FW] ; loc ; [ALL-LOCKS] as lock-final 62 63(* 64 * Put lock operations in their appropriate classes, but leave UL out of W 65 * until after the co relation has been generated. 66 *) 67let R = R | LKR | LF | RU 68let W = W | LKW 69 70let Release = Release | UL 71let Acquire = Acquire | LKR 72 73(* Match LKW events to their corresponding UL events *) 74let critical = ([LKW] ; po-loc ; [UL]) \ (po-loc ; [LKW | UL] ; po-loc) 75 76flag ~empty UL \ range(critical) as unmatched-unlock 77 78(* Allow up to one unmatched LKW per location; more must deadlock *) 79let UNMATCHED-LKW = LKW \ domain(critical) 80empty ([UNMATCHED-LKW] ; loc ; [UNMATCHED-LKW]) \ id as unmatched-locks 81 82(* rfi for LF events: link each LKW to the LF events in its critical section *) 83let rfi-lf = ([LKW] ; po-loc ; [LF]) \ ([LKW] ; po-loc ; [UL] ; po-loc) 84 85(* rfe for LF events *) 86let all-possible-rfe-lf = 87 (* 88 * Given an LF event r, compute the possible rfe edges for that event 89 * (all those starting from LKW events in other threads), 90 * and then convert that relation to a set of single-edge relations. 91 *) 92 let possible-rfe-lf r = 93 let pair-to-relation p = p ++ 0 94 in map pair-to-relation ((LKW * {r}) & loc & ext) 95 (* Do this for each LF event r that isn't in rfi-lf *) 96 in map possible-rfe-lf (LF \ range(rfi-lf)) 97 98(* Generate all rf relations for LF events *) 99with rfe-lf from cross(all-possible-rfe-lf) 100let rf-lf = rfe-lf | rfi-lf 101 102(* 103 * RU, i.e., spin_is_locked() returning False, is slightly different. 104 * We rely on the memory model to rule out cases where spin_is_locked() 105 * within one of the lock's critical sections returns False. 106 *) 107 108(* rfi for RU events: an RU may read from the last po-previous UL *) 109let rfi-ru = ([UL] ; po-loc ; [RU]) \ ([UL] ; po-loc ; [LKW] ; po-loc) 110 111(* rfe for RU events: an RU may read from an external UL or the initial write *) 112let all-possible-rfe-ru = 113 let possible-rfe-ru r = 114 let pair-to-relation p = p ++ 0 115 in map pair-to-relation (((UL | IW) * {r}) & loc & ext) 116 in map possible-rfe-ru RU 117 118(* Generate all rf relations for RU events *) 119with rfe-ru from cross(all-possible-rfe-ru) 120let rf-ru = rfe-ru | rfi-ru 121 122(* Final rf relation *) 123let rf = rf | rf-lf | rf-ru 124 125(* Generate all co relations, including LKW events but not UL *) 126let co0 = co0 | ([IW] ; loc ; [LKW]) | 127 (([LKW] ; loc ; [UNMATCHED-LKW]) \ [UNMATCHED-LKW]) 128include "cos-opt.cat" 129let W = W | UL 130let M = R | W 131 132(* Merge UL events into co *) 133let co = (co | critical | (critical^-1 ; co))+ 134let coe = co & ext 135let coi = co & int 136 137(* Merge LKR events into rf *) 138let rf = rf | ([IW | UL] ; singlestep(co) ; lk-rmw^-1) 139let rfe = rf & ext 140let rfi = rf & int 141 142let fr = rf^-1 ; co 143let fre = fr & ext 144let fri = fr & int 145 146show co,rf,fr 147