diff options
| -rw-r--r-- | tools/memory-model/lock.cat | 51 |
1 files changed, 36 insertions, 15 deletions
diff --git a/tools/memory-model/lock.cat b/tools/memory-model/lock.cat index 1f6d67e79065..df74de2148f6 100644 --- a/tools/memory-model/lock.cat +++ b/tools/memory-model/lock.cat @@ -4,15 +4,35 @@ * Copyright (C) 2017 Alan Stern <stern@rowland.harvard.edu> *) -(* Generate coherence orders and handle lock operations *) (* - * Warning, crashes with herd7 versions strictly before 7.48. - * spin_islocked is functional from version 7.49. + * 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 *) +(* + * 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. + *) + +(* Link Lock-Reads to their RMW-partner Lock-Writes *) let lk-rmw = ([LKR] ; po-loc ; [LKW]) \ (po ; po) let rmw = rmw | lk-rmw @@ -29,18 +49,16 @@ flag ~empty LKW \ range(lk-rmw) as unpaired-LKW (* This will be allowed if we implement spin_is_locked() *) flag ~empty LKR \ domain(lk-rmw) as unpaired-LKR -(* There should be no R or W accesses to spinlocks *) +(* There should be no ordinary R or W accesses to spinlocks *) let ALL-LOCKS = LKR | LKW | UL | LF flag ~empty [M \ IW] ; loc ; [ALL-LOCKS] as mixed-lock-accesses (* The final value of a spinlock should not be tested *) flag ~empty [FW] ; loc ; [ALL-LOCKS] as lock-final -(* - * Backward compatibility - *) -let RL = try RL with emptyset (* defined herd7 >= 7.49 *) -let RU = try RU with emptyset (* defined herd7 >= 7.49 *) +(* Backward compatibility *) +let RL = try RL with emptyset +let RU = try RU with emptyset (* Treat RL as a kind of LF: a read with no ordering properties *) let LF = LF | RL @@ -55,7 +73,6 @@ 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) @@ -65,7 +82,6 @@ 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) @@ -86,18 +102,23 @@ let all-possible-rfe-lf = with rfe-lf from cross(all-possible-rfe-lf) let rf-lf = rfe-lf | rfi-lf -(* Read from unlock, ie islocked returning false, slightly different *) +(* + * 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. + *) -(* islocked returning false can read from the last po-previous unlock *) +(* 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) -(* any islocked returning false can read from any external unlock *) +(* 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 |