| // 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 *) |
| (*******************) |
| |
| (* Release Acquire *) |
| let acq-po = [Acquire] ; po ; [M] |
| let po-rel = [M] ; po ; [Release] |
| let po-unlock-rf-lock-po = po ; [UL] ; rf ; [LKR] ; po |
| |
| (* Fences *) |
| let R4rmb = R \ Noreturn (* Reads for which rmb works *) |
| let rmb = [R4rmb] ; fencerel(Rmb) ; [R4rmb] |
| 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]) | |
| ([M] ; po ; [UL] ; (co | po) ; [LKW] ; |
| fencerel(After-unlock-lock) ; [M]) |
| let gp = po ; [Sync-rcu | Sync-srcu] ; po? |
| let strong-fence = mb | gp |
| |
| let nonrw-fence = strong-fence | po-rel | acq-po |
| let fence = nonrw-fence | wmb | rmb |
| let barrier = fencerel(Barrier | Rmb | Wmb | Mb | Sync-rcu | Sync-srcu | |
| Before-atomic | After-atomic | Acquire | Release | |
| Rcu-lock | Rcu-unlock | Srcu-lock | Srcu-unlock) | |
| (po ; [Release]) | ([Acquire] ; po) |
| |
| (**********************************) |
| (* 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) | (addr ; [Plain] ; wmb) |
| let to-r = addr | (dep ; [Marked] ; rfi) |
| let ppo = to-r | to-w | fence | (po-unlock-rf-lock-po & int) |
| |
| (* Propagation: Ordering from release operations and strong fences. *) |
| let A-cumul(r) = (rfe ; [Marked])? ; r |
| let cumul-fence = [Marked] ; (A-cumul(strong-fence | po-rel) | wmb | |
| po-unlock-rf-lock-po) ; [Marked] |
| let prop = [Marked] ; (overwrite & ext)? ; cumul-fence* ; |
| [Marked] ; rfe? ; [Marked] |
| |
| (* |
| * Happens Before: Ordering from the passage of time. |
| * No fences needed here for prop because relation confined to one process. |
| *) |
| let hb = [Marked] ; (ppo | rfe | ((prop \ id) & int)) ; [Marked] |
| 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* ; [Marked] |
| acyclic pb as propagation |
| |
| (*******) |
| (* RCU *) |
| (*******) |
| |
| (* |
| * Effects of read-side critical sections proceed from the rcu_read_unlock() |
| * or srcu_read_unlock() backwards on the one hand, and from the |
| * rcu_read_lock() or srcu_read_lock() forwards on the other hand. |
| * |
| * In the definition of rcu-fence below, the po term at the left-hand side |
| * of each disjunct and the po? term at the right-hand end have been factored |
| * out. They have been moved into the definitions of rcu-link and rb. |
| * This was necessary in order to apply the "& loc" tests correctly. |
| *) |
| let rcu-gp = [Sync-rcu] (* Compare with gp *) |
| let srcu-gp = [Sync-srcu] |
| let rcu-rscsi = rcu-rscs^-1 |
| let srcu-rscsi = srcu-rscs^-1 |
| |
| (* |
| * 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 = po? ; hb* ; pb* ; prop ; po |
| |
| (* |
| * Any sequence containing at least as many grace periods as RCU read-side |
| * critical sections (joined by rcu-link) induces order like a generalized |
| * inter-CPU strong fence. |
| * Likewise for SRCU grace periods and read-side critical sections, provided |
| * the synchronize_srcu() and srcu_read_[un]lock() calls refer to the same |
| * struct srcu_struct location. |
| *) |
| let rec rcu-order = rcu-gp | srcu-gp | |
| (rcu-gp ; rcu-link ; rcu-rscsi) | |
| ((srcu-gp ; rcu-link ; srcu-rscsi) & loc) | |
| (rcu-rscsi ; rcu-link ; rcu-gp) | |
| ((srcu-rscsi ; rcu-link ; srcu-gp) & loc) | |
| (rcu-gp ; rcu-link ; rcu-order ; rcu-link ; rcu-rscsi) | |
| ((srcu-gp ; rcu-link ; rcu-order ; rcu-link ; srcu-rscsi) & loc) | |
| (rcu-rscsi ; rcu-link ; rcu-order ; rcu-link ; rcu-gp) | |
| ((srcu-rscsi ; rcu-link ; rcu-order ; rcu-link ; srcu-gp) & loc) | |
| (rcu-order ; rcu-link ; rcu-order) |
| let rcu-fence = po ; rcu-order ; po? |
| let fence = fence | rcu-fence |
| let strong-fence = strong-fence | rcu-fence |
| |
| (* rb orders instructions just as pb does *) |
| let rb = prop ; rcu-fence ; hb* ; pb* ; [Marked] |
| |
| 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 |
| *) |
| |
| (*********************************) |
| (* Plain accesses and data races *) |
| (*********************************) |
| |
| (* Warn about plain writes and marked accesses in the same region *) |
| let mixed-accesses = ([Plain & W] ; (po-loc \ barrier) ; [Marked]) | |
| ([Marked] ; (po-loc \ barrier) ; [Plain & W]) |
| flag ~empty mixed-accesses as mixed-accesses |
| |
| (* Executes-before and visibility *) |
| let xbstar = (hb | pb | rb)* |
| let vis = cumul-fence* ; rfe? ; [Marked] ; |
| ((strong-fence ; [Marked] ; xbstar) | (xbstar & int)) |
| |
| (* Boundaries for lifetimes of plain accesses *) |
| let w-pre-bounded = [Marked] ; (addr | fence)? |
| let r-pre-bounded = [Marked] ; (addr | nonrw-fence | |
| ([R4rmb] ; fencerel(Rmb) ; [~Noreturn]))? |
| let w-post-bounded = fence? ; [Marked] |
| let r-post-bounded = (nonrw-fence | ([~Noreturn] ; fencerel(Rmb) ; [R4rmb]))? ; |
| [Marked] |
| |
| (* Visibility and executes-before for plain accesses *) |
| let ww-vis = fence | (strong-fence ; xbstar ; w-pre-bounded) | |
| (w-post-bounded ; vis ; w-pre-bounded) |
| let wr-vis = fence | (strong-fence ; xbstar ; r-pre-bounded) | |
| (w-post-bounded ; vis ; r-pre-bounded) |
| let rw-xbstar = fence | (r-post-bounded ; xbstar ; w-pre-bounded) |
| |
| (* Potential races *) |
| let pre-race = ext & ((Plain * M) | ((M \ IW) * Plain)) |
| |
| (* Coherence requirements for plain accesses *) |
| let wr-incoh = pre-race & rf & rw-xbstar^-1 |
| let rw-incoh = pre-race & fr & wr-vis^-1 |
| let ww-incoh = pre-race & co & ww-vis^-1 |
| empty (wr-incoh | rw-incoh | ww-incoh) as plain-coherence |
| |
| (* Actual races *) |
| let ww-nonrace = ww-vis & ((Marked * W) | rw-xbstar) & ((W * Marked) | wr-vis) |
| let ww-race = (pre-race & co) \ ww-nonrace |
| let wr-race = (pre-race & (co? ; rf)) \ wr-vis \ rw-xbstar^-1 |
| let rw-race = (pre-race & fr) \ rw-xbstar |
| |
| flag ~empty (ww-race | wr-race | rw-race) as data-race |