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locking.tla
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------------------------------ MODULE locking ------------------------------
EXTENDS Naturals, Sequences, TLC
\* Locks = [ Resource |-> Lock ]
\* Lock = [ Granted |-> RequestList, Pending |-> RequestList ]
\* RequestList = [ thread |-> ThreadNames, mode |-> mode ]
\* UnreplicatedOplog = << [ thread |-> ThreadName, op -> OperationName ], ... >>
\* This matrix answers the question, "Is a lock request with mode 'Requested Mode' compatible with
\* an existing lock held in mode 'Granted Mode'?"
\*
\* | Requested Mode | Granted Mode |
\* |----------------|:------------:|:-------:|:--------:|:------:|:--------:|
\* | | MODE_NONE | MODE_IS | MODE_IX | MODE_S | MODE_X |
\* | MODE_IS | + | + | + | + | |
\* | MODE_IX | + | + | + | | |
\* | MODE_S | + | + | | + | |
\* | MODE_X | + | | | | |
\* MODE_NONE is implied by an empty holder list.
CONSTANTS MODE_IS, MODE_IX, MODE_S, MODE_X
CompatibilityMatrix == {
\* IS
<<MODE_IS, MODE_IS>>,
<<MODE_IS, MODE_IX>>,
<<MODE_IS, MODE_S>> ,
\* IX
<<MODE_IX, MODE_IS>>,
<<MODE_IX, MODE_IX>>,
\* S
<<MODE_S, MODE_IS>>,
<<MODE_S, MODE_S>>
}
AllResources == { "DB1", "DB2", "GLOBAL" }
Range(T) == { T[x] : x \in DOMAIN T }
(* --algorithm locking
variables locks = [ r \in AllResources |-> [granted |-> {}, pending |-> {}]], unreplicated_oplog = <<>>;
macro append_to_oplog(op) begin
unreplicated_oplog := Append(unreplicated_oplog, [thread |-> self, op |-> op]);
end macro;
macro wait_for_write_concern(op) begin
await \A entry \in Range(unreplicated_oplog): entry /= [thread |-> self, op |-> op];
end macro;
macro unlock(resource) begin
assert \E request \in locks[resource].granted: request.thread = self;
locks[resource].granted := { r \in locks[resource].granted: r.thread /= self };
end macro;
procedure lock(resource, mode) begin
try_lock:
locks[resource].pending := locks[resource].pending \union {[thread |-> self, mode |-> mode]};
lock_granted:
await \/ locks[resource].granted = {}
\/ /\ \A request \in locks[resource].granted:
<<request.mode, mode>> \in CompatibilityMatrix
/\ \A request \in locks[resource].pending:
request.mode /= MODE_X;
\* self should have been defined in the scope.
locks[resource].pending := { r \in locks[resource].pending: r.thread /= self } ||
locks[resource].granted := locks[resource].granted \union {[thread |-> self, mode |-> mode]};
return;
end procedure;
process ThreadTxn \in {"ThreadTxn"}
begin
\* Start transaction.
TXN_LOCK1: call lock("GLOBAL", MODE_IX);
\* Prepare transaction.
TXN_WRITE: append_to_oplog("prepare-write");
TXN_WC: wait_for_write_concern("prepare-write");
\* Commit transaction.
TXN_UNLOCK1: unlock("GLOBAL");
end process
process ThreadDropDB \in {"ThreadDropDB"}
begin
DROP_DB_LOCK1: call lock("GLOBAL", MODE_X);
DROP_DB_UNLOCK1: unlock("GLOBAL");
end process
process DataReplication \in {"DataReplication"}
begin
DATA_REPL_START:
while TRUE do
if unreplicated_oplog /= <<>> then
REPL_LOCK: call lock("GLOBAL", MODE_IS);
\* Removing elements from the unreplicated_oplog means they have been replicated.
REPL: unreplicated_oplog := Tail(unreplicated_oplog);
REPL_UNLOCK: unlock("GLOBAL");
end if
end while
end process
end algorithm *)
\* BEGIN TRANSLATION
CONSTANT defaultInitValue
VARIABLES locks, unreplicated_oplog, pc, stack, resource, mode
vars == << locks, unreplicated_oplog, pc, stack, resource, mode >>
ProcSet == ({"ThreadTxn"}) \cup ({"ThreadDropDB"}) \cup ({"DataReplication"})
Init == (* Global variables *)
/\ locks = [ r \in AllResources |-> [granted |-> {}, pending |-> {}]]
/\ unreplicated_oplog = <<>>
(* Procedure lock *)
/\ resource = [ self \in ProcSet |-> defaultInitValue]
/\ mode = [ self \in ProcSet |-> defaultInitValue]
/\ stack = [self \in ProcSet |-> << >>]
/\ pc = [self \in ProcSet |-> CASE self \in {"ThreadTxn"} -> "TXN_LOCK1"
[] self \in {"ThreadDropDB"} -> "DROP_DB_LOCK1"
[] self \in {"DataReplication"} -> "DATA_REPL_START"]
try_lock(self) == /\ pc[self] = "try_lock"
/\ locks' = [locks EXCEPT ![resource[self]].pending = locks[resource[self]].pending \union {[thread |-> self, mode |-> mode[self]]}]
/\ pc' = [pc EXCEPT ![self] = "lock_granted"]
/\ UNCHANGED << unreplicated_oplog, stack, resource, mode >>
lock_granted(self) == /\ pc[self] = "lock_granted"
/\ \/ locks[resource[self]].granted = {}
\/ /\ \A request \in locks[resource[self]].granted:
<<request.mode, mode[self]>> \in CompatibilityMatrix
/\ \A request \in locks[resource[self]].pending:
request.mode /= MODE_X
/\ locks' = [locks EXCEPT ![resource[self]].pending = { r \in locks[resource[self]].pending: r.thread /= self },
![resource[self]].granted = locks[resource[self]].granted \union {[thread |-> self, mode |-> mode[self]]}]
/\ pc' = [pc EXCEPT ![self] = Head(stack[self]).pc]
/\ resource' = [resource EXCEPT ![self] = Head(stack[self]).resource]
/\ mode' = [mode EXCEPT ![self] = Head(stack[self]).mode]
/\ stack' = [stack EXCEPT ![self] = Tail(stack[self])]
/\ UNCHANGED unreplicated_oplog
lock(self) == try_lock(self) \/ lock_granted(self)
TXN_LOCK1(self) == /\ pc[self] = "TXN_LOCK1"
/\ /\ mode' = [mode EXCEPT ![self] = MODE_IX]
/\ resource' = [resource EXCEPT ![self] = "GLOBAL"]
/\ stack' = [stack EXCEPT ![self] = << [ procedure |-> "lock",
pc |-> "TXN_WRITE",
resource |-> resource[self],
mode |-> mode[self] ] >>
\o stack[self]]
/\ pc' = [pc EXCEPT ![self] = "try_lock"]
/\ UNCHANGED << locks, unreplicated_oplog >>
TXN_WRITE(self) == /\ pc[self] = "TXN_WRITE"
/\ unreplicated_oplog' = Append(unreplicated_oplog, [thread |-> self, op |-> "prepare-write"])
/\ pc' = [pc EXCEPT ![self] = "TXN_WC"]
/\ UNCHANGED << locks, stack, resource, mode >>
TXN_WC(self) == /\ pc[self] = "TXN_WC"
/\ \A entry \in Range(unreplicated_oplog): entry /= [thread |-> self, op |-> "prepare-write"]
/\ pc' = [pc EXCEPT ![self] = "TXN_UNLOCK1"]
/\ UNCHANGED << locks, unreplicated_oplog, stack, resource,
mode >>
TXN_UNLOCK1(self) == /\ pc[self] = "TXN_UNLOCK1"
/\ Assert(\E request \in locks["GLOBAL"].granted: request.thread = self,
"Failure of assertion at line 50, column 5 of macro called at line 81, column 14.")
/\ locks' = [locks EXCEPT !["GLOBAL"].granted = { r \in locks["GLOBAL"].granted: r.thread /= self }]
/\ pc' = [pc EXCEPT ![self] = "Done"]
/\ UNCHANGED << unreplicated_oplog, stack, resource, mode >>
ThreadTxn(self) == TXN_LOCK1(self) \/ TXN_WRITE(self) \/ TXN_WC(self)
\/ TXN_UNLOCK1(self)
DROP_DB_LOCK1(self) == /\ pc[self] = "DROP_DB_LOCK1"
/\ /\ mode' = [mode EXCEPT ![self] = MODE_X]
/\ resource' = [resource EXCEPT ![self] = "GLOBAL"]
/\ stack' = [stack EXCEPT ![self] = << [ procedure |-> "lock",
pc |-> "DROP_DB_UNLOCK1",
resource |-> resource[self],
mode |-> mode[self] ] >>
\o stack[self]]
/\ pc' = [pc EXCEPT ![self] = "try_lock"]
/\ UNCHANGED << locks, unreplicated_oplog >>
DROP_DB_UNLOCK1(self) == /\ pc[self] = "DROP_DB_UNLOCK1"
/\ Assert(\E request \in locks["GLOBAL"].granted: request.thread = self,
"Failure of assertion at line 50, column 5 of macro called at line 87, column 18.")
/\ locks' = [locks EXCEPT !["GLOBAL"].granted = { r \in locks["GLOBAL"].granted: r.thread /= self }]
/\ pc' = [pc EXCEPT ![self] = "Done"]
/\ UNCHANGED << unreplicated_oplog, stack, resource,
mode >>
ThreadDropDB(self) == DROP_DB_LOCK1(self) \/ DROP_DB_UNLOCK1(self)
DATA_REPL_START(self) == /\ pc[self] = "DATA_REPL_START"
/\ IF unreplicated_oplog /= <<>>
THEN /\ pc' = [pc EXCEPT ![self] = "REPL_LOCK"]
ELSE /\ pc' = [pc EXCEPT ![self] = "DATA_REPL_START"]
/\ UNCHANGED << locks, unreplicated_oplog, stack,
resource, mode >>
REPL_LOCK(self) == /\ pc[self] = "REPL_LOCK"
/\ /\ mode' = [mode EXCEPT ![self] = MODE_IS]
/\ resource' = [resource EXCEPT ![self] = "GLOBAL"]
/\ stack' = [stack EXCEPT ![self] = << [ procedure |-> "lock",
pc |-> "REPL",
resource |-> resource[self],
mode |-> mode[self] ] >>
\o stack[self]]
/\ pc' = [pc EXCEPT ![self] = "try_lock"]
/\ UNCHANGED << locks, unreplicated_oplog >>
REPL(self) == /\ pc[self] = "REPL"
/\ unreplicated_oplog' = Tail(unreplicated_oplog)
/\ pc' = [pc EXCEPT ![self] = "REPL_UNLOCK"]
/\ UNCHANGED << locks, stack, resource, mode >>
REPL_UNLOCK(self) == /\ pc[self] = "REPL_UNLOCK"
/\ Assert(\E request \in locks["GLOBAL"].granted: request.thread = self,
"Failure of assertion at line 50, column 5 of macro called at line 98, column 15.")
/\ locks' = [locks EXCEPT !["GLOBAL"].granted = { r \in locks["GLOBAL"].granted: r.thread /= self }]
/\ pc' = [pc EXCEPT ![self] = "DATA_REPL_START"]
/\ UNCHANGED << unreplicated_oplog, stack, resource, mode >>
DataReplication(self) == DATA_REPL_START(self) \/ REPL_LOCK(self)
\/ REPL(self) \/ REPL_UNLOCK(self)
Next == (\E self \in ProcSet: lock(self))
\/ (\E self \in {"ThreadTxn"}: ThreadTxn(self))
\/ (\E self \in {"ThreadDropDB"}: ThreadDropDB(self))
\/ (\E self \in {"DataReplication"}: DataReplication(self))
Spec == Init /\ [][Next]_vars
\* END TRANSLATION
=============================================================================
\* Modification History
\* Last modified Sat Sep 28 09:51:08 EDT 2019 by emptysquare
\* Last modified Wed Sep 18 23:41:52 EDT 2019 by syzhou
\* Created Tue Sep 17 18:48:11 EDT 2019 by syzhou