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Allow stack limit to be set at any time
jonroach 9 Jan 2026 13:56
1 contributor
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1#include "coroutine.h"
2#include <assert.h>
3#include <setjmp.h>
4#include <stdbool.h>
5#include <stddef.h>
6#include <stdio.h>
7#include "cor_platform.h"
8
9// see CPython again, this time from ctypes.h
10#if (defined (__SVR4) && defined (__sun)) || defined(COROUTINE_HAVE_ALLOCA_H)
11# include <alloca.h>
12#elif defined(MS_WIN32)
13# include <malloc.h>
14#endif
15
16/* If the system does not define alloca(), we have to hope for a compiler builtin. */
17#ifndef alloca
18# if defined __GNUC__ || (__clang_major__ >= 4)
19# define alloca __builtin_alloca
20# else
21# error "Could not define alloca() on your platform."
22# endif
23#endif
24
25static void Coroutine_RunNext(void);
26static void _Coroutine_Continue(Coroutine *cor, void *value, bool early);
27static unsigned char *StackTopNow(void);
28
29///////////////////////////////////////////////////////////////////////////////
30// 2-way linked lists...
31//
32// Brought inline here to avoid namespace polution
33///////////////////////////////////////////////////////////////////////////////
34
35typedef struct List_Link List_Link;
36struct List_Link {
37 List_Link *next;
38 List_Link *prev;
39};
40
41typedef struct List_Head List_Head;
42struct List_Head {
43 union {
44 struct {
45 List_Link link;
46 List_Link *filler;
47 } fwd;
48 struct {
49 List_Link *filler;
50 List_Link link;
51 } back;
52 };
53};
54
55
56static inline bool List_IsEmpty(
57 const List_Head *list
58){
59 return list->fwd.link.next == &list->back.link;
60}
61
62
63static inline List_Link *List_GetHead(
64 const List_Head *list
65){
66 return List_IsEmpty(list) ? NULL : list->fwd.link.next;
67}
68
69
70static inline List_Link *List_Begin(
71 const List_Head *list
72){
73 return list->fwd.link.next;
74}
75
76
77static inline bool Link_NextIsLink(
78 const List_Link *link
79){
80 return link->next != NULL;
81}
82
83
84static inline List_Link *Link_Next(
85 List_Link *link
86){
87 return link->next;
88}
89
90
91static inline bool Link_PrevIsLink(
92 const List_Link *link
93){
94 return link->prev != NULL;
95}
96
97
98static inline List_Link *Link_Prev(
99 List_Link *link
100){
101 return link->prev;
102}
103
104static inline List_Link *List_GetTail(
105 const List_Head *list
106){
107 return List_IsEmpty(list) ? NULL : list->back.link.prev;
108}
109
110
111#define OFFSETOF(Container, Field) ((char *)&((Container *)4)->Field - (char *)(Container *)4)
112#define List_Link_Container(Container, Link, link) ((Container *)((char *)(link) - OFFSETOF(Container, Link)))
113
114
115static inline void List_Init(
116 List_Head *list
117){
118 list->fwd.link.next = &list->back.link;
119 list->fwd.link.prev = NULL;
120 list->back.link.prev = &list->fwd.link;
121}
122
123
124static inline void Link_AddAfter(
125 List_Link *link,
126 List_Link *after
127){
128 link->next = after->next;
129 link->prev = after;
130 after->next->prev = link;
131 after->next = link;
132}
133
134
135static inline void List_AddHead(
136 List_Head *list,
137 List_Link *link
138){
139 Link_AddAfter(link, &list->fwd.link);
140}
141
142
143static inline void Link_AddBefore(
144 List_Link *link,
145 List_Link *before
146){
147 link->prev = before->prev;
148 link->next = before;
149 before->prev->next = link;
150 before->prev = link;
151}
152
153
154static inline void List_AddTail(
155 List_Head *list,
156 List_Link *link
157){
158 Link_AddBefore(link, &list->back.link);
159}
160
161
162static inline void Link_Remove(
163 List_Link *link
164){
165 link->prev->next = link->next;
166 link->next->prev = link->prev;
167}
168
169///////////////////////////////////////////////////////////////////////////////
170// ...2-way linked lists
171///////////////////////////////////////////////////////////////////////////////
172
173typedef struct Coroutines Coroutines;
174
175enum {
176 Coroutines_Starting,
177 Coroutines_Started,
178 Coroutines_Active,
179 Coroutines_Stopping
180};
181
182enum {
183 Chunk_Initial,
184 Chunk_Create,
185 Chunk_Split,
186 Chunk_Enter
187};
188
189typedef enum Coroutine_State {
190 Coroutine_Free,
191 Coroutine_Idle,
192 Coroutine_Running,
193 Coroutine_Waiting,
194 Coroutine_Complete
195} Coroutine_State;
196
197enum {
198 Coroutines_Init,
199 Coroutines_AllocatedChunk,
200 Coroutines_CoroutineComplete,
201};
202
203struct Coroutine {
204 Coroutines *coroutines; // so can work with it off-thread
205 List_Link link; // for whichever list it's on
206 List_Link all_link; // list of all Coroutines
207 jmp_buf buf; // how to get back to it
208 unsigned char *prev_limit; // the previous Coroutine's stack limit
209 unsigned char *base; // where the base (high address) of this Coroutine's stack is
210 unsigned char *limit; // where the limit (low address) of this Coroutine's stack is
211 unsigned char *guard; // where the stack overrun guard is
212 size_t size;
213 Coroutine_Start start; // entry point
214 void *entry_param; // to pass to start
215 void *value; // yielded/returned
216 unsigned char *stack_top; // recorded at yield
217 Coroutine_State state;
218};
219
220struct Coroutines {
221 _Cor_Mutex mutex;
222 jmp_buf controller; // to return from Coroutine_Run
223 jmp_buf chunk_allocated;// for chunk allocation
224 size_t gap_before; // bytes between previous's stack_top and next's Coroutine
225 size_t gap_after; // bytes between Coroutine and stack_base
226
227 // singletons
228 Coroutine *tip; // top of stack chunk
229 Coroutine *active; // currently running coroutine
230 Coroutine *primary; // Coroutine_Run coroutine
231 unsigned char *stack_limit; // when not NULL, where the stack finishes
232
233 // lists
234 List_Head all; // all Coroutines (in address order)
235 List_Head free; // free Coroutines
236 List_Head inactive; // idle or complete
237 List_Head runable; // running or waiting to run
238 List_Head waiting; // yielded / waiting to run
239 _Cor_Mutex waiting_mutex;
240
241 // Summary of the system
242 Coroutine_Report report;
243
244 // state
245 char state;
246};
247
248_Cor_thread_local Coroutines *g_c;
249_Cor_thread_local unsigned char *g_stack_limit;
250
251static void ReserveStackSpace(Coroutines *cors, Coroutine *parent, size_t chunk_size, unsigned char *childs_limit);
252static void stack_chunk_base(Coroutines *cors, Coroutine *parent, unsigned char *prev_limit, unsigned char *limit);
253
254
255#define GUARD_PATTERN_SIZE (4)
256// Check whether the guard is intact
257static inline bool Check_Guard(
258 unsigned char *guard
259){
260 return !guard ||
261 (guard[0] == 0xde &&
262 guard[1] == 0xad &&
263 guard[2] == 0xbe &&
264 guard[3] == 0xef);
265}
266
267
268static inline void Apply_Guard(unsigned char *guard){
269 guard[0] = 0xde;
270 guard[1] = 0xad;
271 guard[2] = 0xbe;
272 guard[3] = 0xef;
273}
274
275
276static bool Coroutine_StackHasOverrun(void){
277 unsigned char *stack_top = StackTopNow();
278 unsigned char *stack_limit = g_c ? g_c->stack_limit : NULL;
279 if (stack_limit && stack_top < stack_limit){
280 // current stack top is beyond limit - we are overrunning NOW
281 return true;
282 }
283 Coroutine *me = g_c ? g_c->active : NULL;
284 if (!me){
285 return false;
286 }
287 if (me->guard){
288 return !Check_Guard(me->guard);
289 }
290 return stack_top < me->limit;
291}
292
293
294static void ReserveStackSpace(
295 Coroutines *cors,
296 Coroutine *parent,
297 size_t chunk_size,
298 unsigned char *childs_limit
299){
300 unsigned char *chunk_of_stack = alloca(chunk_size);
301#if COROUTINE_RECORD_LOWEST_HEADROOM
302 for (size_t i = 0; i <= chunk_size-GUARD_PATTERN_SIZE; i += GUARD_PATTERN_SIZE){
303 Apply_Guard(&chunk_of_stack[i]);
304 }
305#else
306 Apply_Guard(chunk_of_stack);
307#endif
308 if (parent){
309 parent->guard = chunk_of_stack;
310 parent->limit = chunk_of_stack;
311 parent->base = chunk_of_stack + chunk_size;
312 }
313 stack_chunk_base(cors, parent, chunk_of_stack, childs_limit);
314}
315
316
317static void stack_chunk_base(
318 Coroutines *cors,
319 Coroutine *parent,
320 unsigned char *prev_limit,
321 unsigned char *limit
322){
323 Coroutine here;
324 here.coroutines = cors;
325 here.state = Coroutine_Free;
326 here.prev_limit = prev_limit;
327 here.size = 0;
328 here.base = NULL;
329 here.guard = limit;
330 here.limit = limit;
331 if (limit){
332 here.base = (unsigned char *)&here - cors->gap_after;
333 here.size = here.base - here.limit;
334 Apply_Guard(limit);
335 }
336
337 // insert into all list
338 if (parent){
339 Link_AddAfter(&here.all_link, &parent->all_link);
340 } else {
341 List_AddHead(&cors->all, &here.all_link);
342 }
343 // add to free list
344 List_AddTail(&cors->free, &here.link);
345
346 cors->report.coroutines_pool_size += 1;
347
348 if (!cors->tip || &here < cors->tip){
349 cors->tip = &here;
350 }
351
352 for(;;){
353 switch (setjmp(here.buf)) {
354 case Chunk_Initial:
355 if (here.state == Coroutine_Free){
356 // return to the coroutine allocator
357 longjmp(cors->chunk_allocated, 1);
358 } else {
359 assert(here.state == Coroutine_Complete);
360 // we finish here to ensure the setjmp is redone
361 if (cors->primary == &here) {
362 // if primary coroutine - return to Coroutine_Run
363 longjmp(cors->controller, Coroutines_CoroutineComplete);
364 }
365 _Cor_Mutex_Unlock(&cors->mutex);
366 Coroutine_RunNext();
367 assert(false);
368 }
369 case Chunk_Create:
370 // Request to create a new chunk on the stack
371 // We're here if the coroutine is:
372 // Allocated, but not 'run' (Coroutine_Idle)
373 // Run, but not not entered yet (Coroutine_Running)
374 // Completed (Coroutine_Complete)
375 // Free, and the coroutines system is starting - we're characterising the system
376 assert(here.state == Coroutine_Idle ||
377 here.state == Coroutine_Running ||
378 here.state == Coroutine_Complete ||
379 (here.state == Coroutine_Free && cors->state == Coroutines_Starting));
380 ReserveStackSpace(here.coroutines, &here, here.size, NULL);
381 assert(false);
382 case Chunk_Split:
383 // Request to split this free block into two
384 // here.size will be set to our shorter size
385 ReserveStackSpace(here.coroutines, &here, here.size, here.limit);
386 assert(false);
387 case Chunk_Enter:
388 // request to start a coroutine (ie use the chunk for a coroutine)
389 // arrive here with mutex locked
390 assert(here.state == Coroutine_Running);
391 here.coroutines->active = &here;
392 _Cor_Mutex_Unlock(&cors->mutex);
393 here.value = here.start(here.entry_param);
394
395 // check the guard
396 assert(Check_Guard(here.guard));
397
398 _Cor_Mutex_Lock(&here.coroutines->mutex);
399 here.coroutines->active = NULL;
400 assert(here.state == Coroutine_Running);
401 Link_Remove(&here.link);
402 here.state = Coroutine_Complete;
403 List_AddTail(&here.coroutines->inactive, &here.link);
404 // Coroutine has completed
405 // Loop round to redo the setjmp() - if this coroutine yielded, then the setjmp will
406 // need reseting
407 }
408 }
409}
410
411
412static void Coroutine_RunNext(void)
413{
414 // arrive here with mutex unlocked
415 _Cor_Mutex_Lock(&g_c->waiting_mutex);
416 _Cor_Mutex_Lock(&g_c->mutex);
417 Coroutine *next = List_Link_Container(Coroutine, link, List_GetHead(&g_c->runable));
418 assert(next->state == Coroutine_Running);
419 longjmp(next->buf, Chunk_Enter);
420 assert(false);
421}
422
423
424void Coroutine_StartSystem(void)
425{
426 assert(!g_c);
427
428 Coroutines *cors = _Cor_Malloc(sizeof(*g_c));
429 assert(cors);
430
431 cors->state = Coroutines_Starting;
432 _Cor_Mutex_ctor(&cors->mutex);
433
434 cors->tip = NULL;
435 cors->active = NULL;
436 cors->primary = NULL;
437 cors->stack_limit = g_stack_limit;
438
439 List_Init(&cors->all);
440 List_Init(&cors->free);
441 List_Init(&cors->inactive);
442 List_Init(&cors->runable);
443 List_Init(&cors->waiting);
444 _Cor_Mutex_ctor(&cors->waiting_mutex);
445 _Cor_Mutex_Lock(&cors->waiting_mutex);
446
447 cors->report.coroutines_created = 0;
448 cors->report.coroutines_pool_size = 0;
449 cors->report.largest_stack = 0;
450
451 // Charactersize the system...
452 if (!setjmp(cors->chunk_allocated)){
453 ReserveStackSpace(cors, NULL, COROUTINE_STARTUP_STACK_SIZE, NULL);
454 }
455 Coroutine *cor = List_Link_Container(Coroutine, link, List_GetHead(&cors->free));
456 cor->size = COROUTINE_STARTUP_STACK_SIZE;
457 if (!setjmp(cors->chunk_allocated)){
458 longjmp(cor->buf, Chunk_Create);
459 }
460 cors->gap_before = cor->prev_limit - (unsigned char *)cor;
461 cors->gap_after = (unsigned char *)cor - cor->base;
462 // ...charactersize the system
463
464 // discard what we've just created
465 List_Init(&cors->all);
466 List_Init(&cors->free);
467 cors->tip = NULL;
468
469 cors->state = Coroutines_Started;
470
471 g_c = cors;
472}
473
474
475void Coroutine_SetStackLimit(void *limit){
476 assert(!limit || !g_c || !(g_c->state == Coroutines_Started || g_c->state == Coroutines_Active) || (unsigned char *)limit < (unsigned char *)g_c->tip || !g_c->tip);
477 g_stack_limit = limit;
478 if (g_c){
479 g_c->stack_limit = limit;
480 }
481}
482
483
484Coroutine_Report Coroutine_StopSystem(void)
485{
486 assert(g_c);
487 assert(g_c->state == Coroutines_Started);
488 _Cor_Mutex_Lock(&g_c->mutex);
489 g_c->state = Coroutines_Stopping;
490
491 uintptr_t stackminheadroom;
492#if COROUTINE_RECORD_LOWEST_HEADROOM
493 stackminheadroom = g_c->report.largest_stack;
494 for (List_Link *link = g_c->free.fwd.link.next; Link_NextIsLink(link); link = Link_Next(link)){
495 Coroutine *cor = List_Link_Container(Coroutine, link, link);
496 if (cor->guard){
497 for (uintptr_t i = 4; i < cor->size-3; i += 4){
498 if (!Check_Guard(&cor->guard[i])){
499 stackminheadroom = i < stackminheadroom ? i : stackminheadroom;
500 break;
501 }
502 }
503 }
504 }
505#else
506 stackminheadroom = 0;
507#endif
508 g_c->report.lowest_headroom = stackminheadroom;
509
510 assert(List_IsEmpty(&g_c->inactive));
511 _Cor_Mutex_Unlock(&g_c->waiting_mutex);
512 _Cor_Mutex_dtor(&g_c->waiting_mutex);
513
514 assert(g_c->state == Coroutines_Stopping);
515 _Cor_Mutex_Unlock(&g_c->mutex);
516 _Cor_Mutex_dtor(&g_c->mutex);
517
518 Coroutine_Report ret = g_c->report;
519
520 _Cor_Free(g_c);
521 g_c = NULL;
522
523 return ret;
524}
525
526
527void Coroutine_Run_Coroutine(
528 Coroutine *cor,
529 void *value
530){
531 Coroutines *cors = cor->coroutines;
532
533 // Can't Coroutine_Run_Coroutine() off-thread
534 assert(g_c == cors);
535
536 _Cor_Mutex_Lock(&cors->mutex);
537 assert(cors->state == Coroutines_Started);
538 cors->state = Coroutines_Active;
539 cors->primary = cor;
540
541 _Coroutine_Continue(cor, value, true);
542
543 if (!setjmp(cors->controller)){
544 _Cor_Mutex_Unlock(&cors->mutex);
545
546 // start the first coroutine
547 Coroutine_RunNext();
548 }
549 // arrive here with mutex locked
550 assert(List_IsEmpty(&cors->runable));
551 assert(List_IsEmpty(&cors->waiting));
552 assert(cors->state == Coroutines_Active);
553 cors->state = Coroutines_Started;
554 _Cor_Mutex_Unlock(&cors->mutex);
555}
556
557
558bool Coroutine_Run(
559 size_t stack,
560 Coroutine_Start start,
561 void *value,
562 void **result
563){
564 if (g_c && g_c->active){
565 void *res = start(value);
566 if (result){
567 *result = res;
568 }
569 // no failures, so...
570 return false;
571 }
572 assert(!g_c || g_c->state == Coroutines_Started);
573 bool need_start = !g_c;
574 if (need_start){
575 Coroutine_StartSystem();
576 }
577 Coroutine *cor = Coroutine_New(stack, start);
578 if (!cor){
579 // that didn't work
580 return true;
581 }
582 Coroutine_Run_Coroutine(cor, value);
583 if (result){
584 *result = Coroutine_GetValue(cor);
585 }
586 Coroutine_Delete(cor);
587 if (need_start){
588 Coroutine_StopSystem();
589 }
590 // no failures, so...
591 return false;
592}
593
594
595static void Coroutine_FreeToIdle(
596 Coroutine *cor,
597 Coroutine_Start start
598){
599 assert(cor->state == Coroutine_Free);
600 cor->state = Coroutine_Idle;
601 cor->start = start;
602 cor->value = NULL;
603 Link_Remove(&cor->link);
604 List_AddHead(&g_c->inactive, &cor->link);
605
606 g_c->report.coroutines_created += 1;
607}
608
609
610static void Coroutine_FreeToIdleSize(
611 Coroutine *cor,
612 Coroutine_Start start,
613 size_t size
614){
615 assert(!cor->guard);
616 cor->size = size;
617 cor->base = (unsigned char *)cor - g_c->gap_after;
618 cor->limit = cor->base - cor->size;
619 Coroutine_FreeToIdle(cor, start);
620}
621
622
623static Coroutine *Coroutine_New_Lock_Assumed(
624 size_t size,
625 Coroutine_Start start
626){
627 List_Link *link;
628
629 if (!g_c->tip){
630 // no tip - time to create one
631
632 // we're the non-Coroutine which starts the Coroutine system.
633 // Add a single free block
634 if (!setjmp(g_c->chunk_allocated)){
635 ReserveStackSpace(g_c, NULL, COROUTINE_STARTUP_STACK_SIZE, NULL);
636 }
637 }
638
639 Coroutine *cor = NULL;
640 for (link = List_Begin(&g_c->free); Link_NextIsLink(link); link = Link_Next(link)){
641 Coroutine *candidate = List_Link_Container(Coroutine, link, link);
642 if (!candidate->guard) {
643 // this must be the tip
644 assert(candidate == g_c->tip);
645
646 // If this is the only Coroutine in the system, go ahead and use it regardless of size.
647 // Note: there can only be one free block if there's no other sort of blocks as we merge on free
648 if (List_IsEmpty(&g_c->inactive) &&
649 List_IsEmpty(&g_c->runable) &&
650 List_IsEmpty(&g_c->waiting) ){
651 if (g_c->stack_limit){
652 size_t available = (unsigned char *)candidate - g_c->stack_limit - g_c->gap_after;
653 size = available < size ? available : size;
654 }
655 Coroutine_FreeToIdleSize(candidate, start, size);
656 return candidate;
657 }
658
659 // Not the only coroutine in the system - check size
660 if (g_c->stack_limit){
661 // there's a limit - see what that space allows....
662 size_t available = (unsigned char *)candidate - g_c->stack_limit - g_c->gap_after;
663
664 if (available < size){
665 // not enough space for this coroutine
666 return NULL;
667 }
668
669 if (available < size + g_c->gap_before + g_c->gap_after + COROUTINE_MINIMUM_STACK_SIZE) {
670 // not enough space for another coroutine - use all the space for this one
671 size = available;
672 }
673 }
674 Coroutine_FreeToIdleSize(candidate, start, size);
675 return candidate;
676 }
677 if (candidate->size >= size && candidate > cor){
678 // chunk big enough, and a better choice than cor
679 cor = candidate;
680 }
681 }
682
683 if (cor){
684 // - work out whether we're splitting or using the whole chunk
685 if (cor->size >= size + g_c->gap_before + g_c->gap_after + COROUTINE_MINIMUM_STACK_SIZE){
686 // enough space for a second coroutine so split this free block
687 cor->size = size;
688 if (!setjmp(g_c->chunk_allocated)){
689 longjmp(cor->buf, Chunk_Split);
690 }
691 }
692 // cor now ready to use
693 Coroutine_FreeToIdle(cor, start);
694 return cor;
695 }
696
697 // No big-enough free blocks - check if there's space beyond the tip block
698
699 if (g_c->stack_limit) {
700 ptrdiff_t available = (unsigned char *)g_c->tip->limit - g_c->gap_before - g_c->gap_after - g_c->stack_limit;
701 if (available < (ptrdiff_t)size){
702 // no space for a new stack block
703 return NULL;
704 }
705 }
706 Coroutine *tip = g_c->tip;
707 Coroutine *me = g_c->active;
708 if (tip == me) {
709 if (!setjmp(g_c->chunk_allocated)){
710 ReserveStackSpace(g_c, me, StackTopNow() - me->limit, NULL);
711 }
712 } else {
713 if (!setjmp(g_c->chunk_allocated)){
714 longjmp(tip->buf, Chunk_Create);
715 }
716 }
717
718 cor = List_Link_Container(Coroutine, link, List_GetTail(&g_c->free));
719 assert(cor->state == Coroutine_Free);
720 cor->size = size;
721 cor->limit = (unsigned char *)cor - g_c->gap_after - size;
722 cor->state = Coroutine_Idle;
723 cor->start = start;
724 cor->value = NULL;
725 Link_Remove(&cor->link);
726 List_AddHead(&g_c->inactive, &cor->link);
727
728 g_c->report.coroutines_created += 1;
729 return cor;
730}
731
732
733Coroutine *Coroutine_New(
734 size_t stack,
735 Coroutine_Start start
736){
737 assert(g_c);
738 assert((g_c->state == Coroutines_Started && List_IsEmpty(&g_c->inactive)) || g_c->state == Coroutines_Active);
739 assert(!Coroutine_StackHasOverrun());
740
741 _Cor_Mutex_Lock(&g_c->mutex);
742
743 Coroutine *cor = Coroutine_New_Lock_Assumed(stack, start);
744
745 if (cor && cor->size > g_c->report.largest_stack){
746 g_c->report.largest_stack = cor->size;
747 }
748
749 _Cor_Mutex_Unlock(&g_c->mutex);
750
751 return cor;
752}
753
754
755void Coroutine_Delete(
756 Coroutine *cor
757){
758 assert(!Coroutine_StackHasOverrun());
759 if (cor){
760 Coroutines *cors = cor->coroutines;
761 _Cor_Mutex_Lock(&cors->mutex);
762 assert(cor->state == Coroutine_Idle || cor->state == Coroutine_Complete);
763 cor->state = Coroutine_Free;
764 Link_Remove(&cor->link);
765
766 // insert into free list
767 List_AddHead(&cors->free, &cor->link);
768
769 // Check for merge with following Coroutine
770 List_Link *link = Link_Next(&cor->all_link);
771 if (Link_NextIsLink(link)){
772 Coroutine *listcor = List_Link_Container(Coroutine, all_link, link);
773 if (listcor->state == Coroutine_Free){
774 // merge
775 cor->size += cor->limit - listcor->limit;
776 cor->limit = listcor->limit;
777 cor->guard = listcor->guard;
778 Link_Remove(&listcor->all_link);
779 Link_Remove(&listcor->link);
780 if (g_c->tip == listcor){
781 g_c->tip = cor;
782 }
783 }
784 }
785
786 // check for merge with prev coroutine
787 link = Link_Prev(&cor->all_link);
788 if (Link_PrevIsLink(link)){
789 Coroutine *listcor = List_Link_Container(Coroutine, all_link, link);
790 if (listcor->state == Coroutine_Free){
791 // merge
792 listcor->size += listcor->limit - cor->limit;
793 listcor->limit = cor->limit;
794 listcor->guard = cor->guard;
795 Link_Remove(&cor->all_link);
796 Link_Remove(&cor->link);
797 if (g_c->tip == cor){
798 g_c->tip = listcor;
799 }
800 }
801 }
802
803 _Cor_Mutex_Unlock(&cors->mutex);
804 }
805}
806
807
808// Coroutine_Continue, assuming the mutex is claimed
809static void _Coroutine_Continue(
810 Coroutine *cor,
811 void *value,
812 bool early
813){
814 Coroutines *cors = cor->coroutines;
815 assert(cor->state == Coroutine_Idle || cor->state == Coroutine_Waiting);
816 cor->entry_param = value;
817 cor->state = Coroutine_Running;
818 Link_Remove(&cor->link);
819 if ( early ) {
820 List_AddHead(&cors->runable, &cor->link);
821 } else {
822 List_AddTail(&cors->runable, &cor->link);
823 }
824 _Cor_Mutex_Unlock(&cors->waiting_mutex);
825}
826
827
828void Coroutine_Continue(
829 Coroutine *cor,
830 void *value,
831 bool early
832){
833 assert(!Coroutine_StackHasOverrun());
834 Coroutines *cors = cor->coroutines;
835 _Cor_Mutex_Lock(&cors->mutex);
836 _Coroutine_Continue(cor, value, early);
837 _Cor_Mutex_Unlock(&cors->mutex);
838}
839
840
841void *Coroutine_Yield(
842 void *value,
843 Coroutine_YieldCallback on_yield,
844 void *yield_me
845){
846 assert(g_c);
847 Coroutine *me = g_c->active;
848 assert(me);
849 assert(!Coroutine_StackHasOverrun());
850
851 _Cor_Mutex_Lock(&g_c->mutex);
852 Coroutines *cors = me->coroutines;
853 assert(me && me->state == Coroutine_Running && cors == g_c);
854 me->stack_top = StackTopNow();
855 me->value = value;
856 me->state = Coroutine_Waiting;
857
858 Link_Remove(&me->link);
859 if (!List_IsEmpty(&cors->runable)){
860 _Cor_Mutex_Unlock(&cors->waiting_mutex);
861 }
862 List_AddTail(&cors->waiting, &me->link);
863
864 switch (setjmp(me->buf)){
865 case Chunk_Initial:
866 _Cor_Mutex_Unlock(&cors->mutex);
867 on_yield(yield_me);
868 Coroutine_RunNext();
869 assert(false);
870 case Chunk_Create:
871 assert(me == g_c->tip);
872 ReserveStackSpace(me->coroutines, me, me->stack_top - me->limit, NULL);
873 assert(false);
874 case Chunk_Enter:
875 // arrive here with mutex locked
876 cors->active = me;
877 assert(!Coroutine_StackHasOverrun());
878 // when we return here - we are running again
879 assert(me->state == Coroutine_Running);
880 void *res = me->entry_param;
881 _Cor_Mutex_Unlock(&cors->mutex);
882 return res;
883 }
884 return NULL;
885}
886
887
888void *Coroutine_GetValue(
889 Coroutine *cor
890){
891 return cor->value;
892}
893
894
895Coroutine *Coroutine_GetActive(void)
896{
897 return g_c ? g_c->active : NULL;
898}
899
900
901intptr_t Coroutine_GetStackHeadroom(void){
902 assert(g_c);
903 assert(!Coroutine_StackHasOverrun());
904 Coroutine *me = g_c->active;
905 if (!me){
906 // no active coroutine
907 unsigned char *stack_limit = g_c->stack_limit;
908 if (stack_limit){
909 // no stack limit - assume we'll use COROUTINE_STACK_SIZE
910 return StackTopNow() - stack_limit;
911 } else {
912 // no information where the stack ends - return something
913 return COROUTINE_MINIMUM_STACK_SIZE;
914 }
915 }
916 return StackTopNow() - me->limit;
917}
918
919
920// This is used to avoid compiler warnings about returning the address of a local
921static inline void *StopAddressWarnings(void *p)
922{
923 return p;
924}
925
926
927void *Coroutine_GetStackHWM(void){
928 assert(g_c);
929 assert(g_c->state == Coroutines_Active);
930 assert(!Coroutine_StackHasOverrun());
931 // Find where the guards end
932 unsigned char *guard;
933 for (guard = g_c->active->guard; Check_Guard(guard); guard += 4){
934 // do nothing
935 }
936 return guard;
937}
938
939
940void Coroutine_ClearStackForHWM(void){
941 assert(g_c);
942 assert(g_c->state == Coroutines_Active);
943 assert(!Coroutine_StackHasOverrun());
944 unsigned char *end = StackTopNow() - GUARD_PATTERN_SIZE;
945 for (unsigned char *guard = g_c->active->guard+GUARD_PATTERN_SIZE; guard <= end; guard += GUARD_PATTERN_SIZE){
946 Apply_Guard(guard);
947 }
948}
949
950
951static bool Coroutine_CanStartCoroutine_Lock_Assumed(
952 size_t size
953){
954 assert(g_c);
955 assert(g_c->state == Coroutines_Started || g_c->state == Coroutines_Active);
956 assert(!Coroutine_StackHasOverrun());
957
958 if (!g_c->stack_limit){
959 return true;
960 }
961
962 if (!g_c->tip){
963 return true;
964 }
965
966 if (g_c->tip->state == Coroutine_Free){
967 // last block is free
968 if ((unsigned char *)g_c->tip - g_c->stack_limit >= (ptrdiff_t)(g_c->gap_after + size)){
969 // enough room in free block, which is the last block
970 return true;
971 }
972 } else {
973 // last block is allocated
974 if (g_c->tip->limit - g_c->stack_limit >= (ptrdiff_t)(g_c->gap_before + g_c->gap_after + size)){
975 // enough room after the last block, which is allocated
976 return true;
977 }
978 }
979
980 // not enough room between allocated blocks and stack limit, so check free list
981 List_Link *link;
982 for (link = List_Begin(&g_c->free); Link_NextIsLink(link); link = Link_Next(link)){
983 Coroutine *cor = List_Link_Container(Coroutine, link, link);
984 if (cor->size >= size){
985 return true;
986 }
987 }
988
989 return false;
990}
991
992
993bool Coroutine_CanStartCoroutine(
994 size_t size
995){
996 _Cor_Mutex_Lock(&g_c->mutex);
997
998 bool result = Coroutine_CanStartCoroutine_Lock_Assumed(size);
999
1000 _Cor_Mutex_Unlock(&g_c->mutex);
1001
1002 return result;
1003}
1004
1005void *Coroutine_GetCStackTop(void){
1006 assert(!Coroutine_StackHasOverrun());
1007 if ((g_c->state == Coroutines_Started || g_c->state == Coroutines_Active) && g_c->tip != g_c->active) {
1008 return g_c->tip->stack_top;
1009 } else {
1010 return StackTopNow();
1011 }
1012}
1013
1014
1015static unsigned char *StackTopNow(void){
1016 unsigned char here[4];
1017 return StopAddressWarnings(here);
1018}
1019
1020
1021struct Coroutine_ChainParam {
1022 Coroutine_Start start;
1023 void *value;
1024 Coroutine *ret;
1025};
1026
1027
1028static void *Coroutine_ChainFn(
1029 void *param
1030){
1031 struct Coroutine_ChainParam *params = (struct Coroutine_ChainParam *)param;
1032 Coroutine_Continue(params->ret, params->start(params->value), true);
1033 return NULL;
1034}
1035
1036
1037static void Coroutine_ChainYield(
1038 void *unused
1039){
1040 (void)unused;
1041}
1042
1043
1044bool Coroutine_Chain(
1045 size_t size,
1046 Coroutine_Start start,
1047 void *value,
1048 void **result
1049){
1050 assert(Check_Guard(Coroutine_GetActive()->guard));
1051 Coroutine *cor = Coroutine_New(size, Coroutine_ChainFn);
1052 if (!cor){
1053 // failed
1054 return true;
1055 }
1056 struct Coroutine_ChainParam params = {
1057 start,
1058 value,
1059 Coroutine_GetActive()
1060 };
1061 Coroutine_Continue(cor, &params, true);
1062 void *res = Coroutine_Yield(NULL, Coroutine_ChainYield, NULL);
1063 Coroutine_Delete(cor);
1064 if (result){
1065 *result = res;
1066 }
1067 // success!
1068 return false;
1069}
1070
1071
1072bool Coroutine_IsRunning(
1073 Coroutine *cor
1074)
1075{
1076 int state = cor->state;
1077 return state == Coroutine_Running || state == Coroutine_Waiting;
1078}
1079
1080
1081bool Coroutine_IsComplete(
1082 Coroutine *cor
1083)
1084{
1085 int state = cor->state;
1086 return state == Coroutine_Complete;
1087}
1088
1089
1090bool Coroutine_IsStarted(void){
1091 return g_c && (g_c->state == Coroutines_Active || g_c->state == Coroutines_Started);
1092}
1093
1094void _Coroutine_Dump(void){
1095 char *state_to_text[] = {
1096 "Free",
1097 "Idle",
1098 "Running",
1099 "Waiting",
1100 "Complete"
1101 };
1102 unsigned idx = 0;
1103 List_Link *link;
1104 for (link = List_Begin(&g_c->all); Link_NextIsLink(link); link = Link_Next(link)){
1105 Coroutine *cor = List_Link_Container(Coroutine, all_link, link);
1106 printf("%d) %p (%s) %ld%s\n", idx++, cor, state_to_text[cor->state], cor->size, cor == g_c->tip ? " (TIP)" : "");
1107 }
1108}
1109