131 lines
3.9 KiB
Plaintext
131 lines
3.9 KiB
Plaintext
// SPDX-License-Identifier: GPL-2.0+
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(*
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* Copyright (C) 2015 Jade Alglave <j.alglave@ucl.ac.uk>,
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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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* Andrea Parri <parri.andrea@gmail.com>
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*
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* An earlier version of this file appeared in the companion webpage for
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* "Frightening small children and disconcerting grown-ups: Concurrency
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* in the Linux kernel" by Alglave, Maranget, McKenney, Parri, and Stern,
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* which appeared in ASPLOS 2018.
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*)
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"Linux-kernel memory consistency model"
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(*
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* File "lock.cat" handles locks and is experimental.
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* It can be replaced by include "cos.cat" for tests that do not use locks.
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*)
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include "lock.cat"
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(*******************)
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(* Basic relations *)
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(*******************)
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(* Fences *)
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let rmb = [R \ Noreturn] ; fencerel(Rmb) ; [R \ Noreturn]
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let wmb = [W] ; fencerel(Wmb) ; [W]
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let mb = ([M] ; fencerel(Mb) ; [M]) |
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([M] ; fencerel(Before-atomic) ; [RMW] ; po? ; [M]) |
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([M] ; po? ; [RMW] ; fencerel(After-atomic) ; [M]) |
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([M] ; po? ; [LKW] ; fencerel(After-spinlock) ; [M]) |
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([M] ; po ; [UL] ; (co | po) ; [LKW] ;
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fencerel(After-unlock-lock) ; [M])
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let gp = po ; [Sync-rcu] ; po?
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let strong-fence = mb | gp
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(* Release Acquire *)
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let acq-po = [Acquire] ; po ; [M]
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let po-rel = [M] ; po ; [Release]
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let po-unlock-rf-lock-po = po ; [UL] ; rf ; [LKR] ; po
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(**********************************)
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(* Fundamental coherence ordering *)
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(**********************************)
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(* Sequential Consistency Per Variable *)
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let com = rf | co | fr
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acyclic po-loc | com as coherence
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(* Atomic Read-Modify-Write *)
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empty rmw & (fre ; coe) as atomic
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(**********************************)
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(* Instruction execution ordering *)
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(**********************************)
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(* Preserved Program Order *)
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let dep = addr | data
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let rwdep = (dep | ctrl) ; [W]
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let overwrite = co | fr
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let to-w = rwdep | (overwrite & int)
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let to-r = addr | (dep ; rfi)
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let fence = strong-fence | wmb | po-rel | rmb | acq-po
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let ppo = to-r | to-w | fence | (po-unlock-rf-lock-po & int)
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(* Propagation: Ordering from release operations and strong fences. *)
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let A-cumul(r) = rfe? ; r
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let cumul-fence = A-cumul(strong-fence | po-rel) | wmb | po-unlock-rf-lock-po
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let prop = (overwrite & ext)? ; cumul-fence* ; rfe?
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(*
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* Happens Before: Ordering from the passage of time.
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* No fences needed here for prop because relation confined to one process.
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*)
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let hb = ppo | rfe | ((prop \ id) & int)
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acyclic hb as happens-before
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(****************************************)
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(* Write and fence propagation ordering *)
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(****************************************)
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(* Propagation: Each non-rf link needs a strong fence. *)
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let pb = prop ; strong-fence ; hb*
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acyclic pb as propagation
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(*******)
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(* RCU *)
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(*******)
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(*
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* Effect of read-side critical section proceeds from the rcu_read_lock()
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* onward on the one hand and from the rcu_read_unlock() backwards on the
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* other hand.
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*)
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let rscs = po ; crit^-1 ; po?
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(*
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* The synchronize_rcu() strong fence is special in that it can order not
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* one but two non-rf relations, but only in conjunction with an RCU
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* read-side critical section.
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*)
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let rcu-link = hb* ; pb* ; prop
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(*
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* Any sequence containing at least as many grace periods as RCU read-side
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* critical sections (joined by rcu-link) acts as a generalized strong fence.
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*)
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let rec rcu-fence = gp |
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(gp ; rcu-link ; rscs) |
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(rscs ; rcu-link ; gp) |
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(gp ; rcu-link ; rcu-fence ; rcu-link ; rscs) |
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(rscs ; rcu-link ; rcu-fence ; rcu-link ; gp) |
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(rcu-fence ; rcu-link ; rcu-fence)
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(* rb orders instructions just as pb does *)
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let rb = prop ; rcu-fence ; hb* ; pb*
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irreflexive rb as rcu
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(*
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* The happens-before, propagation, and rcu constraints are all
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* expressions of temporal ordering. They could be replaced by
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* a single constraint on an "executes-before" relation, xb:
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*
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* let xb = hb | pb | rb
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* acyclic xb as executes-before
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*)
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