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203 lines
7.1 KiB
203 lines
7.1 KiB
// SPDX-License-Identifier: GPL-2.0+ |
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(* |
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* Copyright (C) 2015 Jade Alglave <[email protected]>, |
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* Copyright (C) 2016 Luc Maranget <[email protected]> for Inria |
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* Copyright (C) 2017 Alan Stern <[email protected]>, |
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* Andrea Parri <[email protected]> |
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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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(* 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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(* Fences *) |
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let R4rmb = R \ Noreturn (* Reads for which rmb works *) |
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let rmb = [R4rmb] ; fencerel(Rmb) ; [R4rmb] |
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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 | Sync-srcu] ; po? |
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let strong-fence = mb | gp |
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let nonrw-fence = strong-fence | po-rel | acq-po |
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let fence = nonrw-fence | wmb | rmb |
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let barrier = fencerel(Barrier | Rmb | Wmb | Mb | Sync-rcu | Sync-srcu | |
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Before-atomic | After-atomic | Acquire | Release | |
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Rcu-lock | Rcu-unlock | Srcu-lock | Srcu-unlock) | |
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(po ; [Release]) | ([Acquire] ; 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) | (addr ; [Plain] ; wmb) |
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let to-r = addr | (dep ; [Marked] ; rfi) |
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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 ; [Marked])? ; r |
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let cumul-fence = [Marked] ; (A-cumul(strong-fence | po-rel) | wmb | |
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po-unlock-rf-lock-po) ; [Marked] |
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let prop = [Marked] ; (overwrite & ext)? ; cumul-fence* ; |
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[Marked] ; rfe? ; [Marked] |
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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 = [Marked] ; (ppo | rfe | ((prop \ id) & int)) ; [Marked] |
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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* ; [Marked] |
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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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* Effects of read-side critical sections proceed from the rcu_read_unlock() |
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* or srcu_read_unlock() backwards on the one hand, and from the |
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* rcu_read_lock() or srcu_read_lock() forwards on the other hand. |
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* |
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* In the definition of rcu-fence below, the po term at the left-hand side |
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* of each disjunct and the po? term at the right-hand end have been factored |
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* out. They have been moved into the definitions of rcu-link and rb. |
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* This was necessary in order to apply the "& loc" tests correctly. |
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*) |
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let rcu-gp = [Sync-rcu] (* Compare with gp *) |
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let srcu-gp = [Sync-srcu] |
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let rcu-rscsi = rcu-rscs^-1 |
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let srcu-rscsi = srcu-rscs^-1 |
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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 = po? ; hb* ; pb* ; prop ; po |
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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) induces order like a generalized |
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* inter-CPU strong fence. |
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* Likewise for SRCU grace periods and read-side critical sections, provided |
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* the synchronize_srcu() and srcu_read_[un]lock() calls refer to the same |
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* struct srcu_struct location. |
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*) |
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let rec rcu-order = rcu-gp | srcu-gp | |
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(rcu-gp ; rcu-link ; rcu-rscsi) | |
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((srcu-gp ; rcu-link ; srcu-rscsi) & loc) | |
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(rcu-rscsi ; rcu-link ; rcu-gp) | |
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((srcu-rscsi ; rcu-link ; srcu-gp) & loc) | |
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(rcu-gp ; rcu-link ; rcu-order ; rcu-link ; rcu-rscsi) | |
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((srcu-gp ; rcu-link ; rcu-order ; rcu-link ; srcu-rscsi) & loc) | |
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(rcu-rscsi ; rcu-link ; rcu-order ; rcu-link ; rcu-gp) | |
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((srcu-rscsi ; rcu-link ; rcu-order ; rcu-link ; srcu-gp) & loc) | |
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(rcu-order ; rcu-link ; rcu-order) |
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let rcu-fence = po ; rcu-order ; po? |
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let fence = fence | rcu-fence |
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let strong-fence = strong-fence | rcu-fence |
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(* rb orders instructions just as pb does *) |
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let rb = prop ; rcu-fence ; hb* ; pb* ; [Marked] |
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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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(*********************************) |
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(* Plain accesses and data races *) |
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(*********************************) |
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(* Warn about plain writes and marked accesses in the same region *) |
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let mixed-accesses = ([Plain & W] ; (po-loc \ barrier) ; [Marked]) | |
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([Marked] ; (po-loc \ barrier) ; [Plain & W]) |
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flag ~empty mixed-accesses as mixed-accesses |
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(* Executes-before and visibility *) |
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let xbstar = (hb | pb | rb)* |
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let vis = cumul-fence* ; rfe? ; [Marked] ; |
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((strong-fence ; [Marked] ; xbstar) | (xbstar & int)) |
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(* Boundaries for lifetimes of plain accesses *) |
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let w-pre-bounded = [Marked] ; (addr | fence)? |
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let r-pre-bounded = [Marked] ; (addr | nonrw-fence | |
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([R4rmb] ; fencerel(Rmb) ; [~Noreturn]))? |
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let w-post-bounded = fence? ; [Marked] |
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let r-post-bounded = (nonrw-fence | ([~Noreturn] ; fencerel(Rmb) ; [R4rmb]))? ; |
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[Marked] |
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(* Visibility and executes-before for plain accesses *) |
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let ww-vis = fence | (strong-fence ; xbstar ; w-pre-bounded) | |
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(w-post-bounded ; vis ; w-pre-bounded) |
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let wr-vis = fence | (strong-fence ; xbstar ; r-pre-bounded) | |
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(w-post-bounded ; vis ; r-pre-bounded) |
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let rw-xbstar = fence | (r-post-bounded ; xbstar ; w-pre-bounded) |
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(* Potential races *) |
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let pre-race = ext & ((Plain * M) | ((M \ IW) * Plain)) |
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(* Coherence requirements for plain accesses *) |
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let wr-incoh = pre-race & rf & rw-xbstar^-1 |
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let rw-incoh = pre-race & fr & wr-vis^-1 |
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let ww-incoh = pre-race & co & ww-vis^-1 |
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empty (wr-incoh | rw-incoh | ww-incoh) as plain-coherence |
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(* Actual races *) |
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let ww-nonrace = ww-vis & ((Marked * W) | rw-xbstar) & ((W * Marked) | wr-vis) |
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let ww-race = (pre-race & co) \ ww-nonrace |
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let wr-race = (pre-race & (co? ; rf)) \ wr-vis \ rw-xbstar^-1 |
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let rw-race = (pre-race & fr) \ rw-xbstar |
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flag ~empty (ww-race | wr-race | rw-race) as data-race
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