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