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034fb712a6
Currently, herdtools version information appears no fewer than three times in the LKMM source, which is difficult to maintain. This commit therefore places the required version in one place, namely the tools/memory-model/README file. Signed-off-by: Andrea Parri <andrea.parri@amarulasolutions.com> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Acked-by: Alan Stern <stern@rowland.harvard.edu>
145 lines
4.8 KiB
Text
145 lines
4.8 KiB
Text
// 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 | Sync-srcu] ; 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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* 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) acts as a generalized 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-fence = 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-fence ; rcu-link ; rcu-rscsi) |
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((srcu-gp ; rcu-link ; rcu-fence ; rcu-link ; srcu-rscsi) & loc) |
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(rcu-rscsi ; rcu-link ; rcu-fence ; rcu-link ; rcu-gp) |
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((srcu-rscsi ; rcu-link ; rcu-fence ; rcu-link ; srcu-gp) & loc) |
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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 ; po ; rcu-fence ; po? ; 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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