5d0989a860
Further clojure.core.cache fixes (198 -> 257 of its assertions): - delay: a throwing body re-ran on every force and never became realized?. Run it once like Clojure's Delay — cache the exception, mark realized, re-throw the same on each deref. Fixes value-fn memoization / cache-stampede protection. - deftype/defrecord: a method name appearing in two protocols with different arities (data.priority-map's seq is in IPersistentMap [this] AND Sorted [this asc]) registered per-protocol and shadowed; merge clauses by name across all protocols into one multi-arity fn. - empty?/peek/pop (IPersistentStack) dispatch through a deftype's methods; (= a- deftype other) uses its equiv method (so caches compare to their backing map); seq handles a host iterator (iterator-seq over .iterator). - pop of an empty PersistentQueue returns it, like the JVM (was an error). JVM-certified corpus rows. make test + shakesmoke green.
330 lines
16 KiB
Scheme
330 lines
16 KiB
Scheme
;; concurrency.ss — real OS-thread futures + promises for the Chez host.
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;;
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;; SHARED-HEAP semantics, like JVM Clojure: a future body runs on a native thread
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;; (fork-thread) over the SAME heap, so a captured atom is shared and the body's
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;; mutations are visible to the parent. deref blocks on a mutex+condition latch.
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;;
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;; future / future-call / future-cancel / future? / future-done? / future-cancelled?
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;; promise / deliver, and the deref extension for both, are bound here (some
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;; re-asserted in post-prelude.ss over the overlay's versions).
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;;
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;; pmap / pcalls / pvalues live in the clojure.core overlay (40-lazy) expressed
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;; over `future`, so they light up for free once future-call exists.
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;;
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;; Loaded near the end of rt.ss — after atoms.ss (jolt-deref, the atom lock) and
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;; dyn-binding.ss (the thread-local binding stack we convey into the worker).
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;; Requires a threaded Chez build (fork-thread / make-mutex / make-condition).
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;; --- time helpers -----------------------------------------------------------
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;; A relative duration / absolute deadline from a millisecond count (a jolt number).
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(define (ms->duration ms)
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(let* ((ms* (exact (floor ms)))
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(secs (quotient ms* 1000))
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(nanos (* (remainder ms* 1000) 1000000)))
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(make-time 'time-duration nanos secs)))
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(define (ms->deadline ms) (add-duration (current-time 'time-utc) (ms->duration ms)))
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;; --- futures ----------------------------------------------------------------
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;; A future is a mutable cell guarded by `mu`; workers/derefs coordinate on `cv`.
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;; done? — result (or cancellation) is final; derefs may proceed
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;; cancelled? — future-cancel won before the body finished
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;; ok? — payload is a value (else payload is a raised condition/value)
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;; payload — the result value, or the captured throw
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(define-record-type jolt-future
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(fields (mutable done?) (mutable cancelled?) (mutable ok?) (mutable payload) mu cv)
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(nongenerative jolt-future-v1))
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;; (future-call thunk): spawn a thread running (thunk). The dynamic bindings in
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;; effect now are conveyed into the worker (Chez inherits thread-parameters at
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;; fork; we also install an explicit snapshot for certainty). The result — value
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;; or thrown condition — is latched and broadcast; a cancel that already finalized
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;; the future makes the late result a no-op.
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(define (jolt-future-call thunk)
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(let ((f (make-jolt-future #f #f #f jolt-nil (make-mutex) (make-condition)))
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(snap (dyn-binding-stack)))
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(fork-thread
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(lambda ()
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(dyn-binding-stack snap)
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(let ((r (guard (e (#t (cons #f e))) (cons #t (jolt-invoke thunk)))))
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(with-mutex (jolt-future-mu f)
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(unless (jolt-future-done? f) ; not already cancelled
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(jolt-future-ok?-set! f (car r))
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(jolt-future-payload-set! f (cdr r))
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(jolt-future-done?-set! f #t))
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(condition-broadcast (jolt-future-cv f))))))
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f))
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;; Final value of a settled future (called OUTSIDE the lock): re-raise a captured
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;; throw, signal a cancellation, else the value.
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(define (jolt-future-finish f)
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(cond
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((jolt-future-cancelled? f)
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(jolt-throw (jolt-ex-info "Future cancelled" (jolt-hash-map))))
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((jolt-future-ok? f) (jolt-future-payload f))
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(else (raise (jolt-future-payload f)))))
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(define (jolt-future-deref f)
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(with-mutex (jolt-future-mu f)
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(let loop ()
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(unless (jolt-future-done? f)
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(condition-wait (jolt-future-cv f) (jolt-future-mu f))
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(loop))))
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(jolt-future-finish f))
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;; (deref f timeout-ms timeout-val): wait up to timeout-ms; return timeout-val if
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;; it has not settled by the absolute deadline.
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(define (jolt-future-deref-timed f ms timeout-val)
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(let* ((deadline (ms->deadline ms))
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(settled (with-mutex (jolt-future-mu f)
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(let loop ()
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(cond ((jolt-future-done? f) #t)
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((condition-wait (jolt-future-cv f) (jolt-future-mu f) deadline)
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(loop)) ; woken — recheck
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(else (jolt-future-done? f))))))) ; timed out: final check
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(if settled (jolt-future-finish f) timeout-val)))
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;; future-cancel: the running thread can't be interrupted, but the future object
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;; reflects the cancellation — if not already settled, mark it cancelled+done so
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;; derefs raise and the predicates flip. Returns true iff this call cancelled it.
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(define (jolt-future-cancel f)
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(let ((cancelled (with-mutex (jolt-future-mu f)
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(if (jolt-future-done? f)
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#f
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(begin (jolt-future-cancelled?-set! f #t)
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(jolt-future-done?-set! f #t)
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(condition-broadcast (jolt-future-cv f))
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#t)))))
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cancelled))
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(define (jolt-native-future-done? x)
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(if (jolt-future? x) (jolt-future-done? x)
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(jolt-throw (jolt-ex-info "future-done? requires a future" (jolt-hash-map)))))
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(define (jolt-native-future-cancelled? x)
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(and (jolt-future? x) (jolt-future-cancelled? x)))
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;; --- promises ---------------------------------------------------------------
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;; A blocking promise (like the JVM): deref parks until deliver, then caches the
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;; value. deliver wins once; later delivers return nil.
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(define-record-type jolt-promise
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(fields (mutable delivered?) (mutable value) mu cv)
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(nongenerative jolt-promise-v1))
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(define (jolt-promise-new) (make-jolt-promise #f jolt-nil (make-mutex) (make-condition)))
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(define (jolt-deliver p v)
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(if (jolt-promise? p)
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(let ((won (with-mutex (jolt-promise-mu p)
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(if (jolt-promise-delivered? p)
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#f
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(begin (jolt-promise-value-set! p v)
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(jolt-promise-delivered?-set! p #t)
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(condition-broadcast (jolt-promise-cv p))
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#t)))))
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(if won p jolt-nil))
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(jolt-throw (jolt-ex-info "deliver requires a promise" (jolt-hash-map)))))
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(define (jolt-promise-deref p)
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(with-mutex (jolt-promise-mu p)
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(let loop ()
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(unless (jolt-promise-delivered? p)
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(condition-wait (jolt-promise-cv p) (jolt-promise-mu p))
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(loop))))
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(jolt-promise-value p))
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(define (jolt-promise-deref-timed p ms timeout-val)
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(let* ((deadline (ms->deadline ms))
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(got (with-mutex (jolt-promise-mu p)
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(let loop ()
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(cond ((jolt-promise-delivered? p) #t)
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((condition-wait (jolt-promise-cv p) (jolt-promise-mu p) deadline)
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(loop))
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(else (jolt-promise-delivered? p)))))))
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(if got (jolt-promise-value p) timeout-val)))
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;; --- agents (async, per-agent serialized dispatch) --------------------------
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;; JVM semantics: send/send-off enqueue an action and a single worker thread
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;; applies them to the state IN ORDER; deref reads the
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;; (possibly not-yet-updated) state without blocking; await blocks until the queue
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;; drains. An action error is captured (agent-error) and stops the queue.
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(define-record-type jolt-agent
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(fields (mutable state) (mutable err) (mutable validator)
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(mutable queue) (mutable running?) mu cv)
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(nongenerative jolt-agent-v1))
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;; (agent state) / (agent state :validator f :error-mode m :meta x): only :validator
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;; has runtime behaviour here; other opts are accepted/ignored.
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(define (jolt-agent-new state . opts)
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(let loop ((o opts) (validator jolt-nil))
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(cond
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((or (null? o) (null? (cdr o)))
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(make-jolt-agent state jolt-nil validator (vector '() '()) #f (make-mutex) (make-condition)))
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((and (keyword-t? (car o)) (string=? (keyword-t-name (car o)) "validator"))
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(loop (cddr o) (cadr o)))
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(else (loop (cddr o) validator)))))
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;; The action queue is an amortized-O(1) FIFO held as a mutable #(out in): `out` is
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;; the front, `in` holds sends reversed onto it (an append-to-a-list send was O(n)).
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;; All three helpers run under the agent mutex.
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(define (jagent-q-empty? a)
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(let ((q (jolt-agent-queue a))) (and (null? (vector-ref q 0)) (null? (vector-ref q 1)))))
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(define (jagent-q-push! a entry)
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(let ((q (jolt-agent-queue a))) (vector-set! q 1 (cons entry (vector-ref q 1)))))
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(define (jagent-q-pop! a)
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(let ((q (jolt-agent-queue a)))
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(when (null? (vector-ref q 0))
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(vector-set! q 0 (reverse (vector-ref q 1))) (vector-set! q 1 '()))
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(let ((out (vector-ref q 0))) (vector-set! q 0 (cdr out)) (car out))))
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;; Drain the queue, applying each action (f state arg*) outside the lock (an action
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;; may send/deref the same agent). A validator rejection or a thrown action puts the
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;; agent in an error state and halts the queue (JVM :fail mode).
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(define (jolt-agent-worker a)
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(let loop ()
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(let ((act (with-mutex (jolt-agent-mu a)
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(if (or (not (jolt-nil? (jolt-agent-err a))) (jagent-q-empty? a))
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(begin (jolt-agent-running?-set! a #f)
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(condition-broadcast (jolt-agent-cv a)) #f)
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(jagent-q-pop! a)))))
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(when act
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(guard (e (#t (with-mutex (jolt-agent-mu a)
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(jolt-agent-err-set! a e)
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(condition-broadcast (jolt-agent-cv a)))))
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(let ((nv (apply jolt-invoke (car act) (jolt-agent-state a) (cdr act))))
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(let ((vf (jolt-agent-validator a)))
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(when (and (not (jolt-nil? vf)) (jolt-not (jolt-invoke vf nv)))
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(error #f "Invalid reference state")))
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(jolt-agent-state-set! a nv)))
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(loop)))))
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;; send / send-off: enqueue the action, start the worker if idle. (jolt treats them
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;; identically — one serialized worker per agent — which is observably a superset of
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;; the JVM's fixed/cached pool split.)
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(define (jolt-agent-send a f . args)
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(with-mutex (jolt-agent-mu a)
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(jagent-q-push! a (cons f args))
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(unless (jolt-agent-running? a)
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(jolt-agent-running?-set! a #t)
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(fork-thread (lambda () (jolt-agent-worker a)))))
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a)
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;; (await & agents): block until each agent's queue has drained.
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(define (jolt-agent-await . agents)
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(for-each
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(lambda (a)
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(with-mutex (jolt-agent-mu a)
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(let loop ()
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(when (or (jolt-agent-running? a) (not (jagent-q-empty? a)))
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(condition-wait (jolt-agent-cv a) (jolt-agent-mu a)) (loop)))))
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agents)
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jolt-nil)
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(define (jolt-agent-error a) (jolt-agent-err a))
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(define (jolt-agent-restart a new-state . _opts)
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(jolt-agent-err-set! a jolt-nil)
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(jolt-agent-state-set! a new-state)
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a)
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;; --- delay (lazy once-forced computation) -----------------------------------
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;; (delay body) -> (make-delay (fn [] body)) (overlay macro); force/deref run the
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;; thunk once under a lock and cache the value (JVM delays are thread-safe). force
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;; (overlay) is (if (delay? x) (deref x) x), so it works once delay?/deref do.
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(define-record-type jolt-delay (fields thunk (mutable realized?) (mutable value) (mutable exn) mu)
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(nongenerative jolt-delay-v1))
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(define (jolt-make-delay thunk) (make-jolt-delay thunk #f jolt-nil #f (make-mutex)))
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;; run the thunk once, like Clojure's Delay: if it throws, cache the exception
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;; (the delay IS realized) and re-throw it on every deref — do NOT re-run the
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;; body (so value-fns memoize and there is no cache-stampede / retried side
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;; effect). Store the exception inside the lock, re-raise outside it so the mutex
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;; is always released.
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(define (jolt-delay-force d)
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(with-mutex (jolt-delay-mu d)
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(unless (jolt-delay-realized? d)
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(guard (e (#t (jolt-delay-exn-set! d e) (jolt-delay-realized?-set! d #t)))
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(jolt-delay-value-set! d (jolt-invoke (jolt-delay-thunk d)))
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(jolt-delay-realized?-set! d #t))))
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(if (jolt-delay-exn d) (raise (jolt-delay-exn d)) (jolt-delay-value d)))
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;; --- deref extension --------------------------------------------------------
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;; Chain the fully-built jolt-deref (atoms/vars/volatiles/reduced) with futures,
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;; promises, agents, and delays; accept the timed (deref ref ms val) arity for the
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;; blocking ref types.
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(define %pre-conc-deref jolt-deref)
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(set! jolt-deref
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(lambda (x . opts)
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(cond
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((jolt-future? x)
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(if (null? opts) (jolt-future-deref x)
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(jolt-future-deref-timed x (car opts) (cadr opts))))
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((jolt-promise? x)
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(if (null? opts) (jolt-promise-deref x)
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(jolt-promise-deref-timed x (car opts) (cadr opts))))
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((jolt-agent? x) (jolt-agent-state x))
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((jolt-delay? x) (jolt-delay-force x))
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(else (apply %pre-conc-deref x opts)))))
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;; realized? for a future/promise/delay. Wrapped over the overlay version in
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;; post-prelude.ss.
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(define (jolt-conc-realized? x)
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(cond ((jolt-future? x) (jolt-future-done? x))
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((jolt-promise? x) (jolt-promise-delivered? x))
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((jolt-delay? x) (jolt-delay-realized? x))
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(else #f)))
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;; --- bind into clojure.core -------------------------------------------------
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(def-var! "clojure.core" "future-call" jolt-future-call)
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(def-var! "clojure.core" "future-cancel" jolt-future-cancel)
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(def-var! "clojure.core" "future?" jolt-future?)
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(def-var! "clojure.core" "future-done?" jolt-native-future-done?)
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(def-var! "clojure.core" "future-cancelled?" jolt-native-future-cancelled?)
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(def-var! "clojure.core" "promise" jolt-promise-new)
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(def-var! "clojure.core" "deliver" jolt-deliver)
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(def-var! "clojure.core" "agent" jolt-agent-new)
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(def-var! "clojure.core" "agent?" jolt-agent?)
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(def-var! "clojure.core" "send" jolt-agent-send)
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(def-var! "clojure.core" "send-off" jolt-agent-send)
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(def-var! "clojure.core" "await" jolt-agent-await)
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(def-var! "clojure.core" "agent-error" jolt-agent-error)
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(def-var! "clojure.core" "restart-agent" jolt-agent-restart)
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(def-var! "clojure.core" "make-delay" jolt-make-delay)
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(def-var! "clojure.core" "delay?" jolt-delay?)
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(def-var! "clojure.core" "deref" jolt-deref)
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;; --- cooperative thread interrupt -------------------------------------------
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;; Chez has no force-kill, but its engine timer (set-timer + timer-interrupt-
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;; handler, thread-local) is polled at procedure-call / loop back-edges — so a
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;; running computation, even a tight Scheme loop, can be aborted from another
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;; thread. An interrupt TOKEN is a shared box; run-interruptible arms a periodic
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;; timer in the eval thread whose handler escapes (via call/cc) when the token is
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;; set; interrupt! sets the token from any thread. The aborted eval throws a jolt
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;; ex-info {:jolt/interrupted true}, so the thread is REUSED, not abandoned.
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;;
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;; Caveat: a thread blocked in a __collect_safe foreign call (socket recv/accept,
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;; sleep) only sees the interrupt when it returns to Scheme — like the JVM not
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;; killing native code.
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(define interrupt-check-ticks 100000) ; ~poll interval; responsive + low overhead
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(define interrupt-sentinel (cons 'jolt 'interrupted))
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(define jolt-kw-interrupted (keyword "jolt" "interrupted"))
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(define (jolt-make-interrupt) (box #f))
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(define (jolt-interrupt! token) (when (box? token) (set-box! token #t)) jolt-nil)
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(define (jolt-interrupted? token) (and (box? token) (unbox token) #t))
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(define (jolt-run-interruptible token thunk)
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(let ((prev-handler (timer-interrupt-handler)))
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(let ((r (call/cc
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(lambda (k)
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(timer-interrupt-handler
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(lambda ()
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(if (and (box? token) (unbox token))
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(k interrupt-sentinel)
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(begin (set-timer interrupt-check-ticks) (void)))))
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(set-timer interrupt-check-ticks)
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(let ((v (thunk))) (set-timer 0) v)))))
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;; restore the prior timer state regardless of outcome.
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(set-timer 0)
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(timer-interrupt-handler prev-handler)
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(if (eq? r interrupt-sentinel)
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(jolt-throw (jolt-ex-info "Evaluation interrupted" (jolt-hash-map jolt-kw-interrupted #t)))
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r))))
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(def-var! "jolt.host" "make-interrupt" jolt-make-interrupt)
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(def-var! "jolt.host" "interrupt!" jolt-interrupt!)
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(def-var! "jolt.host" "interrupted?" jolt-interrupted?)
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(def-var! "jolt.host" "run-interruptible" jolt-run-interruptible)
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