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fix problem with continuations

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The problem was a misplaced allocation that could cause a GC
when the thread is in an unstable state in the process of
applying a continuation.
This commit is contained in:
Matthew Flatt 2012-02-28 11:18:13 -07:00
parent 249c1cc666
commit 70ab6d482a
2 changed files with 19 additions and 4 deletions
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11
collects/tests/racket/prompt-tests.rktl
View File

@ -1993,6 +1993,17 @@
(sync (thread (lambda () (k 6))))
(void)))
(test (void)
'capture-in-transferred-thread/values
(let ([k (call-with-continuation-prompt
(lambda ()
(let/ec esc
(define-values (a b) (call/cc esc))
(+ a b)
(call/cc values))))])
(sync (thread (lambda () (k 6 7))))
(void)))
(let ()
(define sema (make-semaphore 1))
(define l null)

12
src/racket/src/eval.c
View File

@ -1520,8 +1520,9 @@ Scheme_Object *scheme_jump_to_continuation(Scheme_Object *obj, int num_rands, Sc
MZ_RUNSTACK = old_runstack;
return scheme_compose_continuation(c, num_rands, value);
} else {
/* Aborting (Racket-style) continuation. */
/* Aborting (Scheme-style) continuation. */
int orig_cac = scheme_continuation_application_count;
Scheme_Overflow *thread_end_oflow;
scheme_about_to_move_C_stack();
@ -1550,6 +1551,9 @@ Scheme_Object *scheme_jump_to_continuation(Scheme_Object *obj, int num_rands, Sc
c->common_dw_depth = common_depth;
/* in case we need it (since no allocation allowed later): */
thread_end_oflow = scheme_get_thread_end_overflow();
if (num_rands == 1)
c->value = value;
else {
@ -1558,6 +1562,8 @@ Scheme_Object *scheme_jump_to_continuation(Scheme_Object *obj, int num_rands, Sc
c->value = vals;
}
/* !! No allocation or GCs allowed from here to the longjmp() !! */
c->common_dw = common;
c->common_next_meta = p->next_meta;
@ -1578,9 +1584,7 @@ Scheme_Object *scheme_jump_to_continuation(Scheme_Object *obj, int num_rands, Sc
/* Prompt is pseudo-prompt at thread beginning.
We're effectively composing the continuation,
so use its prompt stack start. */
Scheme_Overflow *oflow;
oflow = scheme_get_thread_end_overflow();
c->resume_to = oflow;
c->resume_to = thread_end_oflow;
p->stack_start = c->prompt_stack_start;
}
scheme_longjmpup(&c->buf);