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 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 *)
 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