// SPDX-License-Identifier: GPL-2.0+ (* * Copyright (C) 2015 Jade Alglave , * Copyright (C) 2016 Luc Maranget for Inria * Copyright (C) 2017 Alan Stern , * Andrea Parri * * 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) acts as a generalized 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-fence = 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-fence ; rcu-link ; rcu-rscsi) | ((srcu-gp ; rcu-link ; rcu-fence ; rcu-link ; srcu-rscsi) & loc) | (rcu-rscsi ; rcu-link ; rcu-fence ; rcu-link ; rcu-gp) | ((srcu-rscsi ; rcu-link ; rcu-fence ; rcu-link ; srcu-gp) & loc) | (rcu-fence ; rcu-link ; rcu-fence) (* rb orders instructions just as pb does *) let rb = prop ; po ; rcu-fence ; po? ; 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 full-fence = strong-fence | (po ; rcu-fence ; po?) let vis = cumul-fence* ; rfe? ; [Marked] ; ((full-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 = w-post-bounded ; vis ; w-pre-bounded let wr-vis = w-post-bounded ; vis ; r-pre-bounded let rw-xbstar = 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 let rw-race = (pre-race & fr) \ rw-xbstar flag ~empty (ww-race | wr-race | rw-race) as data-race