diff options
Diffstat (limited to 'tools/memory-model/lock.cat')
| -rw-r--r-- | tools/memory-model/lock.cat | 107 |
1 files changed, 77 insertions, 30 deletions
diff --git a/tools/memory-model/lock.cat b/tools/memory-model/lock.cat index ba4a4ec6d313..305ded17e741 100644 --- a/tools/memory-model/lock.cat +++ b/tools/memory-model/lock.cat @@ -4,46 +4,72 @@ * Copyright (C) 2017 Alan Stern <stern@rowland.harvard.edu> *) -(* Generate coherence orders and handle lock operations *) +(* + * Generate coherence orders and handle lock operations + * + * Warning: spin_is_locked() crashes herd7 versions strictly before 7.48. + * spin_is_locked() is functional from herd7 version 7.49. + *) include "cross.cat" -(* From lock reads to their partner lock writes *) -let lk-rmw = ([LKR] ; po-loc ; [LKW]) \ (po ; po) -let rmw = rmw | lk-rmw - (* - * A paired LKR must always see an unlocked value; spin_lock() calls nested - * inside a critical section (for the same lock) always deadlock. + * The lock-related events generated by herd are as follows: + * + * LKR Lock-Read: the read part of a spin_lock() or successful + * spin_trylock() read-modify-write event pair + * LKW Lock-Write: the write part of a spin_lock() or successful + * spin_trylock() RMW event pair + * UL Unlock: a spin_unlock() event + * LF Lock-Fail: a failed spin_trylock() event + * RL Read-Locked: a spin_is_locked() event which returns True + * RU Read-Unlocked: a spin_is_locked() event which returns False + * + * LKR and LKW events always come paired, like all RMW event sequences. + * + * LKR, LF, RL, and RU are read events; LKR has Acquire ordering. + * LKW and UL are write events; UL has Release ordering. + * LKW, LF, RL, and RU have no ordering properties. *) -empty ([LKW] ; po-loc ; [domain(lk-rmw)]) \ (po-loc ; [UL] ; po-loc) - as lock-nest -(* The litmus test is invalid if an LKW event is not part of an RMW pair *) -flag ~empty LKW \ range(lk-rmw) as unpaired-LKW +(* Backward compatibility *) +let RL = try RL with emptyset +let RU = try RU with emptyset -(* This will be allowed if we implement spin_is_locked() *) -flag ~empty LKR \ domain(lk-rmw) as unpaired-LKR +(* Treat RL as a kind of LF: a read with no ordering properties *) +let LF = LF | RL -(* There should be no R or W accesses to spinlocks *) -let ALL-LOCKS = LKR | LKW | UL | LF +(* There should be no ordinary R or W accesses to spinlocks *) +let ALL-LOCKS = LKR | LKW | UL | LF | RU flag ~empty [M \ IW] ; loc ; [ALL-LOCKS] as mixed-lock-accesses +(* Link Lock-Reads to their RMW-partner Lock-Writes *) +let lk-rmw = ([LKR] ; po-loc ; [LKW]) \ (po ; po) +let rmw = rmw | lk-rmw + +(* The litmus test is invalid if an LKR/LKW event is not part of an RMW pair *) +flag ~empty LKW \ range(lk-rmw) as unpaired-LKW +flag ~empty LKR \ domain(lk-rmw) as unpaired-LKR + +(* + * An LKR must always see an unlocked value; spin_lock() calls nested + * inside a critical section (for the same lock) always deadlock. + *) +empty ([LKW] ; po-loc ; [LKR]) \ (po-loc ; [UL] ; po-loc) as lock-nest + (* The final value of a spinlock should not be tested *) flag ~empty [FW] ; loc ; [ALL-LOCKS] as lock-final - (* * Put lock operations in their appropriate classes, but leave UL out of W * until after the co relation has been generated. *) -let R = R | LKR | LF +let R = R | LKR | LF | RU let W = W | LKW let Release = Release | UL let Acquire = Acquire | LKR - (* Match LKW events to their corresponding UL events *) let critical = ([LKW] ; po-loc ; [UL]) \ (po-loc ; [LKW | UL] ; po-loc) @@ -53,27 +79,48 @@ flag ~empty UL \ range(critical) as unmatched-unlock let UNMATCHED-LKW = LKW \ domain(critical) empty ([UNMATCHED-LKW] ; loc ; [UNMATCHED-LKW]) \ id as unmatched-locks - (* rfi for LF events: link each LKW to the LF events in its critical section *) let rfi-lf = ([LKW] ; po-loc ; [LF]) \ ([LKW] ; po-loc ; [UL] ; po-loc) (* rfe for LF events *) let all-possible-rfe-lf = - (* - * Given an LF event r, compute the possible rfe edges for that event - * (all those starting from LKW events in other threads), - * and then convert that relation to a set of single-edge relations. - *) - let possible-rfe-lf r = - let pair-to-relation p = p ++ 0 - in map pair-to-relation ((LKW * {r}) & loc & ext) - (* Do this for each LF event r that isn't in rfi-lf *) - in map possible-rfe-lf (LF \ range(rfi-lf)) + (* + * Given an LF event r, compute the possible rfe edges for that event + * (all those starting from LKW events in other threads), + * and then convert that relation to a set of single-edge relations. + *) + let possible-rfe-lf r = + let pair-to-relation p = p ++ 0 + in map pair-to-relation ((LKW * {r}) & loc & ext) + (* Do this for each LF event r that isn't in rfi-lf *) + in map possible-rfe-lf (LF \ range(rfi-lf)) (* Generate all rf relations for LF events *) with rfe-lf from cross(all-possible-rfe-lf) -let rf = rf | rfi-lf | rfe-lf +let rf-lf = rfe-lf | rfi-lf + +(* + * RU, i.e., spin_is_locked() returning False, is slightly different. + * We rely on the memory model to rule out cases where spin_is_locked() + * within one of the lock's critical sections returns False. + *) + +(* rfi for RU events: an RU may read from the last po-previous UL *) +let rfi-ru = ([UL] ; po-loc ; [RU]) \ ([UL] ; po-loc ; [LKW] ; po-loc) + +(* rfe for RU events: an RU may read from an external UL or the initial write *) +let all-possible-rfe-ru = + let possible-rfe-ru r = + let pair-to-relation p = p ++ 0 + in map pair-to-relation (((UL | IW) * {r}) & loc & ext) + in map possible-rfe-ru RU + +(* Generate all rf relations for RU events *) +with rfe-ru from cross(all-possible-rfe-ru) +let rf-ru = rfe-ru | rfi-ru +(* Final rf relation *) +let rf = rf | rf-lf | rf-ru (* Generate all co relations, including LKW events but not UL *) let co0 = co0 | ([IW] ; loc ; [LKW]) | |