| // SPDX-License-Identifier: GPL-2.0+ |
| (* |
| * Copyright (C) 2015 Jade Alglave <j.alglave@ucl.ac.uk>, |
| * Copyright (C) 2016 Luc Maranget <luc.maranget@inria.fr> for Inria |
| * Copyright (C) 2017 Alan Stern <stern@rowland.harvard.edu>, |
| * Andrea Parri <parri.andrea@gmail.com> |
| * |
| * An earlier version of this file appeared in the companion webpage for |
| * "Frightening small children and disconcerting grown-ups: Concurrency |
| * in the Linux kernel" by Alglave, Maranget, McKenney, Parri, and Stern, |
| * which appeared in ASPLOS 2018. |
| *) |
| |
| "Linux-kernel memory consistency model" |
| |
| (* |
| * File "lock.cat" handles locks and is experimental. |
| * It can be replaced by include "cos.cat" for tests that do not use locks. |
| *) |
| |
| include "lock.cat" |
| |
| (*******************) |
| (* Basic relations *) |
| (*******************) |
| |
| (* Fences *) |
| let rmb = [R \ Noreturn] ; fencerel(Rmb) ; [R \ Noreturn] |
| let wmb = [W] ; fencerel(Wmb) ; [W] |
| let mb = ([M] ; fencerel(Mb) ; [M]) | |
| ([M] ; fencerel(Before-atomic) ; [RMW] ; po? ; [M]) | |
| ([M] ; po? ; [RMW] ; fencerel(After-atomic) ; [M]) | |
| ([M] ; po? ; [LKW] ; fencerel(After-spinlock) ; [M]) |
| let gp = po ; [Sync-rcu] ; po? |
| |
| let strong-fence = mb | gp |
| |
| (* Release Acquire *) |
| let acq-po = [Acquire] ; po ; [M] |
| let po-rel = [M] ; po ; [Release] |
| let rfi-rel-acq = [Release] ; rfi ; [Acquire] |
| |
| (**********************************) |
| (* Fundamental coherence ordering *) |
| (**********************************) |
| |
| (* Sequential Consistency Per Variable *) |
| let com = rf | co | fr |
| acyclic po-loc | com as coherence |
| |
| (* Atomic Read-Modify-Write *) |
| empty rmw & (fre ; coe) as atomic |
| |
| (**********************************) |
| (* Instruction execution ordering *) |
| (**********************************) |
| |
| (* Preserved Program Order *) |
| let dep = addr | data |
| let rwdep = (dep | ctrl) ; [W] |
| let overwrite = co | fr |
| let to-w = rwdep | (overwrite & int) |
| let to-r = addr | (dep ; rfi) | rfi-rel-acq |
| let fence = strong-fence | wmb | po-rel | rmb | acq-po |
| let ppo = to-r | to-w | fence |
| |
| (* Propagation: Ordering from release operations and strong fences. *) |
| let A-cumul(r) = rfe? ; r |
| let cumul-fence = A-cumul(strong-fence | po-rel) | wmb |
| let prop = (overwrite & ext)? ; cumul-fence* ; rfe? |
| |
| (* |
| * Happens Before: Ordering from the passage of time. |
| * No fences needed here for prop because relation confined to one process. |
| *) |
| let hb = ppo | rfe | ((prop \ id) & int) |
| acyclic hb as happens-before |
| |
| (****************************************) |
| (* Write and fence propagation ordering *) |
| (****************************************) |
| |
| (* Propagation: Each non-rf link needs a strong fence. *) |
| let pb = prop ; strong-fence ; hb* |
| acyclic pb as propagation |
| |
| (*******) |
| (* RCU *) |
| (*******) |
| |
| (* |
| * Effect of read-side critical section proceeds from the rcu_read_lock() |
| * onward on the one hand and from the rcu_read_unlock() backwards on the |
| * other hand. |
| *) |
| let rscs = po ; crit^-1 ; po? |
| |
| (* |
| * The synchronize_rcu() strong fence is special in that it can order not |
| * one but two non-rf relations, but only in conjunction with an RCU |
| * read-side critical section. |
| *) |
| let rcu-link = hb* ; pb* ; prop |
| |
| (* |
| * Any sequence containing at least as many grace periods as RCU read-side |
| * critical sections (joined by rcu-link) acts as a generalized strong fence. |
| *) |
| let rec rcu-fence = gp | |
| (gp ; rcu-link ; rscs) | |
| (rscs ; rcu-link ; gp) | |
| (gp ; rcu-link ; rcu-fence ; rcu-link ; rscs) | |
| (rscs ; rcu-link ; rcu-fence ; rcu-link ; gp) | |
| (rcu-fence ; rcu-link ; rcu-fence) |
| |
| (* rb orders instructions just as pb does *) |
| let rb = prop ; rcu-fence ; hb* ; pb* |
| |
| irreflexive rb as rcu |
| |
| (* |
| * The happens-before, propagation, and rcu constraints are all |
| * expressions of temporal ordering. They could be replaced by |
| * a single constraint on an "executes-before" relation, xb: |
| * |
| * let xb = hb | pb | rb |
| * acyclic xb as executes-before |
| *) |