147 lines
4.7 KiB
Plaintext
147 lines
4.7 KiB
Plaintext
// SPDX-License-Identifier: GPL-2.0+
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(*
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* Copyright (C) 2016 Luc Maranget <luc.maranget@inria.fr> for Inria
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* Copyright (C) 2017 Alan Stern <stern@rowland.harvard.edu>
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*)
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(*
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* Generate coherence orders and handle lock operations
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*
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* Warning: spin_is_locked() crashes herd7 versions strictly before 7.48.
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* spin_is_locked() is functional from herd7 version 7.49.
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*)
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include "cross.cat"
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(*
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* The lock-related events generated by herd are as follows:
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*
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* LKR Lock-Read: the read part of a spin_lock() or successful
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* spin_trylock() read-modify-write event pair
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* LKW Lock-Write: the write part of a spin_lock() or successful
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* spin_trylock() RMW event pair
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* UL Unlock: a spin_unlock() event
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* LF Lock-Fail: a failed spin_trylock() event
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* RL Read-Locked: a spin_is_locked() event which returns True
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* RU Read-Unlocked: a spin_is_locked() event which returns False
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*
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* LKR and LKW events always come paired, like all RMW event sequences.
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*
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* LKR, LF, RL, and RU are read events; LKR has Acquire ordering.
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* LKW and UL are write events; UL has Release ordering.
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* LKW, LF, RL, and RU have no ordering properties.
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*)
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(* Backward compatibility *)
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let RL = try RL with emptyset
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let RU = try RU with emptyset
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(* Treat RL as a kind of LF: a read with no ordering properties *)
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let LF = LF | RL
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(* There should be no ordinary R or W accesses to spinlocks *)
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let ALL-LOCKS = LKR | LKW | UL | LF | RU
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flag ~empty [M \ IW] ; loc ; [ALL-LOCKS] as mixed-lock-accesses
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(* Link Lock-Reads to their RMW-partner Lock-Writes *)
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let lk-rmw = ([LKR] ; po-loc ; [LKW]) \ (po ; po)
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let rmw = rmw | lk-rmw
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(* The litmus test is invalid if an LKR/LKW event is not part of an RMW pair *)
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flag ~empty LKW \ range(lk-rmw) as unpaired-LKW
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flag ~empty LKR \ domain(lk-rmw) as unpaired-LKR
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(*
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* An LKR must always see an unlocked value; spin_lock() calls nested
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* inside a critical section (for the same lock) always deadlock.
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*)
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empty ([LKW] ; po-loc ; [LKR]) \ (po-loc ; [UL] ; po-loc) as lock-nest
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(* The final value of a spinlock should not be tested *)
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flag ~empty [FW] ; loc ; [ALL-LOCKS] as lock-final
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(*
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* Put lock operations in their appropriate classes, but leave UL out of W
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* until after the co relation has been generated.
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*)
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let R = R | LKR | LF | RU
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let W = W | LKW
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let Release = Release | UL
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let Acquire = Acquire | LKR
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(* Match LKW events to their corresponding UL events *)
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let critical = ([LKW] ; po-loc ; [UL]) \ (po-loc ; [LKW | UL] ; po-loc)
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flag ~empty UL \ range(critical) as unmatched-unlock
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(* Allow up to one unmatched LKW per location; more must deadlock *)
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let UNMATCHED-LKW = LKW \ domain(critical)
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empty ([UNMATCHED-LKW] ; loc ; [UNMATCHED-LKW]) \ id as unmatched-locks
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(* rfi for LF events: link each LKW to the LF events in its critical section *)
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let rfi-lf = ([LKW] ; po-loc ; [LF]) \ ([LKW] ; po-loc ; [UL] ; po-loc)
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(* rfe for LF events *)
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let all-possible-rfe-lf =
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(*
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* Given an LF event r, compute the possible rfe edges for that event
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* (all those starting from LKW events in other threads),
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* and then convert that relation to a set of single-edge relations.
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*)
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let possible-rfe-lf r =
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let pair-to-relation p = p ++ 0
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in map pair-to-relation ((LKW * {r}) & loc & ext)
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(* Do this for each LF event r that isn't in rfi-lf *)
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in map possible-rfe-lf (LF \ range(rfi-lf))
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(* Generate all rf relations for LF events *)
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with rfe-lf from cross(all-possible-rfe-lf)
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let rf-lf = rfe-lf | rfi-lf
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(*
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* RU, i.e., spin_is_locked() returning False, is slightly different.
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* We rely on the memory model to rule out cases where spin_is_locked()
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* within one of the lock's critical sections returns False.
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*)
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(* rfi for RU events: an RU may read from the last po-previous UL *)
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let rfi-ru = ([UL] ; po-loc ; [RU]) \ ([UL] ; po-loc ; [LKW] ; po-loc)
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(* rfe for RU events: an RU may read from an external UL or the initial write *)
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let all-possible-rfe-ru =
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let possible-rfe-ru r =
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let pair-to-relation p = p ++ 0
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in map pair-to-relation (((UL | IW) * {r}) & loc & ext)
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in map possible-rfe-ru RU
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(* Generate all rf relations for RU events *)
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with rfe-ru from cross(all-possible-rfe-ru)
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let rf-ru = rfe-ru | rfi-ru
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(* Final rf relation *)
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let rf = rf | rf-lf | rf-ru
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(* Generate all co relations, including LKW events but not UL *)
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let co0 = co0 | ([IW] ; loc ; [LKW]) |
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(([LKW] ; loc ; [UNMATCHED-LKW]) \ [UNMATCHED-LKW])
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include "cos-opt.cat"
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let W = W | UL
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let M = R | W
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(* Merge UL events into co *)
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let co = (co | critical | (critical^-1 ; co))+
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let coe = co & ext
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let coi = co & int
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(* Merge LKR events into rf *)
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let rf = rf | ([IW | UL] ; singlestep(co) ; lk-rmw^-1)
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let rfe = rf & ext
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let rfi = rf & int
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let fr = rf^-1 ; co
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let fre = fr & ext
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let fri = fr & int
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show co,rf,fr
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