xref: /linux-6.15/tools/memory-model/linux-kernel.bell (revision dcc51978)

// SPDX-License-Identifier: GPL-2.0+
(*
 * Copyright (C) 2015 Jade Alglave <[email protected]>,
 * Copyright (C) 2016 Luc Maranget <[email protected]> for Inria
 * Copyright (C) 2017 Alan Stern <[email protected]>,
 *                    Andrea Parri <[email protected]>
 *
 * 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"

enum Accesses = 'ONCE (*READ_ONCE,WRITE_ONCE*) ||
		'RELEASE (*smp_store_release*) ||
		'ACQUIRE (*smp_load_acquire*) ||
		'NORETURN (* R of non-return RMW *) ||
		'MB (*xchg(),cmpxchg(),...*)
instructions R[Accesses]
instructions W[Accesses]
instructions RMW[Accesses]

enum Barriers = 'wmb (*smp_wmb*) ||
		'rmb (*smp_rmb*) ||
		'MB (*smp_mb*) ||
		'barrier (*barrier*) ||
		'rcu-lock (*rcu_read_lock*)  ||
		'rcu-unlock (*rcu_read_unlock*) ||
		'sync-rcu (*synchronize_rcu*) ||
		'before-atomic (*smp_mb__before_atomic*) ||
		'after-atomic (*smp_mb__after_atomic*) ||
		'after-spinlock (*smp_mb__after_spinlock*) ||
		'after-unlock-lock (*smp_mb__after_unlock_lock*) ||
		'after-srcu-read-unlock (*smp_mb__after_srcu_read_unlock*)
instructions F[Barriers]


(*
 * Filter out syntactic annotations that do not provide the corresponding
 * semantic ordering, such as Acquire on a store or Mb on a failed RMW.
 *)
let FailedRMW = RMW \ (domain(rmw) | range(rmw))
let Acquire = ACQUIRE \ W \ FailedRMW
let Release = RELEASE \ R \ FailedRMW
let Mb = MB \ FailedRMW
let Noreturn = NORETURN \ W

(* SRCU *)
enum SRCU = 'srcu-lock || 'srcu-unlock || 'sync-srcu
instructions SRCU[SRCU]
(* All srcu events *)
let Srcu = Srcu-lock | Srcu-unlock | Sync-srcu

(* Compute matching pairs of nested Rcu-lock and Rcu-unlock *)
let rcu-rscs = let rec
	    unmatched-locks = Rcu-lock \ domain(matched)
	and unmatched-unlocks = Rcu-unlock \ range(matched)
	and unmatched = unmatched-locks | unmatched-unlocks
	and unmatched-po = [unmatched] ; po ; [unmatched]
	and unmatched-locks-to-unlocks =
		[unmatched-locks] ; po ; [unmatched-unlocks]
	and matched = matched | (unmatched-locks-to-unlocks \
		(unmatched-po ; unmatched-po))
	in matched

(* Validate nesting *)
flag ~empty Rcu-lock \ domain(rcu-rscs) as unmatched-rcu-lock
flag ~empty Rcu-unlock \ range(rcu-rscs) as unmatched-rcu-unlock

(* Compute matching pairs of nested Srcu-lock and Srcu-unlock *)
let carry-srcu-data = (data ; [~ Srcu-unlock] ; rf)*
let srcu-rscs = ([Srcu-lock] ; carry-srcu-data ; data ; [Srcu-unlock]) & loc

(* Validate nesting *)
flag ~empty Srcu-lock \ domain(srcu-rscs) as unmatched-srcu-lock
flag ~empty Srcu-unlock \ range(srcu-rscs) as unmatched-srcu-unlock
flag ~empty (srcu-rscs^-1 ; srcu-rscs) \ id as multiple-srcu-matches

(* Check for use of synchronize_srcu() inside an RCU critical section *)
flag ~empty rcu-rscs & (po ; [Sync-srcu] ; po) as invalid-sleep

(* Validate SRCU dynamic match *)
flag ~empty different-values(srcu-rscs) as srcu-bad-value-match

(* Compute marked and plain memory accesses *)
let Marked = (~M) | IW | ONCE | RELEASE | ACQUIRE | MB | RMW |
		LKR | LKW | UL | LF | RL | RU | Srcu-lock | Srcu-unlock
let Plain = M \ Marked

(* Redefine dependencies to include those carried through plain accesses *)
let carry-dep = (data ; [~ Srcu-unlock] ; rfi)*
let addr = carry-dep ; addr
let ctrl = carry-dep ; ctrl
let data = carry-dep ; data

flag ~empty (if "lkmmv2" then 0 else _)
  as this-model-requires-variant-higher-than-lkmmv1