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jolt.ffi: a :blocking option for collect-safe foreign calls

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A library binding a blocking native call (accept/recv/connect/...) needs it
emitted __collect_safe so the thread deactivates for the call and doesn't pin
the stop-the-world collector. foreign-fn / defcfn take an optional trailing
:blocking; the backend emits (foreign-procedure __collect_safe ...). Needed for
the ring-janet-adapter socket-server port. ffi-binding-test asserts a thread
parked in a :blocking call doesn't block (collect).
This commit is contained in:
Yogthos 2026-06-22 12:00:14 -04:00
parent db9bed226f
commit 2a64e65a1c
5 changed files with 93 additions and 74 deletions
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9
test/chez/ffi-binding-test.ss
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@ -39,5 +39,14 @@
(let [v (jolt.ffi/read p :int)] (jolt.ffi/free p) v))"))))
(ok "sizeof :pointer is a word" (let ((n (jnum->exact (ev "(jolt.ffi/sizeof :pointer)")))) (or (= n 8) (= n 4))))
;; a :blocking foreign call is collect-safe: a thread parked in it must not pin
;; the stop-the-world collector. (collect) here would throw "cannot collect when
;; multiple threads are active" if usleep weren't emitted __collect_safe.
(ev "(def c-usleep (jolt.ffi/__cfn \"usleep\" [:uint] :int :blocking))")
(let ((usleep (var-deref "user" "c-usleep")))
(fork-thread (lambda () (usleep 2000000))) ; ~2s in a blocking call
(let loop ((i 0)) (when (fx<? i 30000000) (loop (fx+ i 1)))) ; spin so the thread enters usleep
(ok "blocking ffi call is collect-safe" (guard (e (#t #f)) (collect) #t)))
(printf "~a/~a passed~n" (- total fails) total)
(exit (if (zero? fails) 0 1))