1/*
2** Garbage collector.
3** Copyright (C) 2005-2014 Mike Pall. See Copyright Notice in luajit.h
4**
5** Major portions taken verbatim or adapted from the Lua interpreter.
6** Copyright (C) 1994-2008 Lua.org, PUC-Rio. See Copyright Notice in lua.h
7*/
8
9#define lj_gc_c
10#define LUA_CORE
11
12#include "lj_obj.h"
13#include "lj_gc.h"
14#include "lj_err.h"
15#include "lj_str.h"
16#include "lj_tab.h"
17#include "lj_func.h"
18#include "lj_udata.h"
19#include "lj_meta.h"
20#include "lj_state.h"
21#include "lj_frame.h"
22#if LJ_HASFFI
23#include "lj_ctype.h"
24#include "lj_cdata.h"
25#endif
26#include "lj_trace.h"
27#include "lj_vm.h"
28
29#define GCSTEPSIZE 1024u
30#define GCSWEEPMAX 40
31#define GCSWEEPCOST 10
32#define GCFINALIZECOST 100
33
34/* Macros to set GCobj colors and flags. */
35#define white2gray(x) ((x)->gch.marked &= (uint8_t)~LJ_GC_WHITES)
36#define gray2black(x) ((x)->gch.marked |= LJ_GC_BLACK)
37#define isfinalized(u) ((u)->marked & LJ_GC_FINALIZED)
38
39/* -- Mark phase ---------------------------------------------------------- */
40
41/* Mark a TValue (if needed). */
42#define gc_marktv(g, tv) \
43 { lua_assert(!tvisgcv(tv) || (~itype(tv) == gcval(tv)->gch.gct)); \
44 if (tviswhite(tv)) gc_mark(g, gcV(tv)); }
45
46/* Mark a GCobj (if needed). */
47#define gc_markobj(g, o) \
48 { if (iswhite(obj2gco(o))) gc_mark(g, obj2gco(o)); }
49
50/* Mark a string object. */
51#define gc_mark_str(s) ((s)->marked &= (uint8_t)~LJ_GC_WHITES)
52
53/* Mark a white GCobj. */
54static void gc_mark(global_State *g, GCobj *o)
55{
56 int gct = o->gch.gct;
57 lua_assert(iswhite(o) && !isdead(g, o));
58 white2gray(o);
59 if (LJ_UNLIKELY(gct == ~LJ_TUDATA)) {
60 GCtab *mt = tabref(gco2ud(o)->metatable);
61 gray2black(o); /* Userdata are never gray. */
62 if (mt) gc_markobj(g, mt);
63 gc_markobj(g, tabref(gco2ud(o)->env));
64 } else if (LJ_UNLIKELY(gct == ~LJ_TUPVAL)) {
65 GCupval *uv = gco2uv(o);
66 gc_marktv(g, uvval(uv));
67 if (uv->closed)
68 gray2black(o); /* Closed upvalues are never gray. */
69 } else if (gct != ~LJ_TSTR && gct != ~LJ_TCDATA) {
70 lua_assert(gct == ~LJ_TFUNC || gct == ~LJ_TTAB ||
71 gct == ~LJ_TTHREAD || gct == ~LJ_TPROTO);
72 setgcrefr(o->gch.gclist, g->gc.gray);
73 setgcref(g->gc.gray, o);
74 }
75}
76
77/* Mark GC roots. */
78static void gc_mark_gcroot(global_State *g)
79{
80 ptrdiff_t i;
81 for (i = 0; i < GCROOT_MAX; i++)
82 if (gcref(g->gcroot[i]) != NULL)
83 gc_markobj(g, gcref(g->gcroot[i]));
84}
85
86/* Start a GC cycle and mark the root set. */
87static void gc_mark_start(global_State *g)
88{
89 setgcrefnull(g->gc.gray);
90 setgcrefnull(g->gc.grayagain);
91 setgcrefnull(g->gc.weak);
92 gc_markobj(g, mainthread(g));
93 gc_markobj(g, tabref(mainthread(g)->env));
94 gc_marktv(g, &g->registrytv);
95 gc_mark_gcroot(g);
96 g->gc.state = GCSpropagate;
97}
98
99/* Mark open upvalues. */
100static void gc_mark_uv(global_State *g)
101{
102 GCupval *uv;
103 for (uv = uvnext(&g->uvhead); uv != &g->uvhead; uv = uvnext(uv)) {
104 lua_assert(uvprev(uvnext(uv)) == uv && uvnext(uvprev(uv)) == uv);
105 if (isgray(obj2gco(uv)))
106 gc_marktv(g, uvval(uv));
107 }
108}
109
110/* Mark userdata in mmudata list. */
111static void gc_mark_mmudata(global_State *g)
112{
113 GCobj *root = gcref(g->gc.mmudata);
114 GCobj *u = root;
115 if (u) {
116 do {
117 u = gcnext(u);
118 makewhite(g, u); /* Could be from previous GC. */
119 gc_mark(g, u);
120 } while (u != root);
121 }
122}
123
124/* Separate userdata objects to be finalized to mmudata list. */
125size_t lj_gc_separateudata(global_State *g, int all)
126{
127 size_t m = 0;
128 GCRef *p = &mainthread(g)->nextgc;
129 GCobj *o;
130 while ((o = gcref(*p)) != NULL) {
131 if (!(iswhite(o) || all) || isfinalized(gco2ud(o))) {
132 p = &o->gch.nextgc; /* Nothing to do. */
133 } else if (!lj_meta_fastg(g, tabref(gco2ud(o)->metatable), MM_gc)) {
134 markfinalized(o); /* Done, as there's no __gc metamethod. */
135 p = &o->gch.nextgc;
136 } else { /* Otherwise move userdata to be finalized to mmudata list. */
137 m += sizeudata(gco2ud(o));
138 markfinalized(o);
139 *p = o->gch.nextgc;
140 if (gcref(g->gc.mmudata)) { /* Link to end of mmudata list. */
141 GCobj *root = gcref(g->gc.mmudata);
142 setgcrefr(o->gch.nextgc, root->gch.nextgc);
143 setgcref(root->gch.nextgc, o);
144 setgcref(g->gc.mmudata, o);
145 } else { /* Create circular list. */
146 setgcref(o->gch.nextgc, o);
147 setgcref(g->gc.mmudata, o);
148 }
149 }
150 }
151 return m;
152}
153
154/* -- Propagation phase --------------------------------------------------- */
155
156/* Traverse a table. */
157static int gc_traverse_tab(global_State *g, GCtab *t)
158{
159 int weak = 0;
160 cTValue *mode;
161 GCtab *mt = tabref(t->metatable);
162 if (mt)
163 gc_markobj(g, mt);
164 mode = lj_meta_fastg(g, mt, MM_mode);
165 if (mode && tvisstr(mode)) { /* Valid __mode field? */
166 const char *modestr = strVdata(mode);
167 int c;
168 while ((c = *modestr++)) {
169 if (c == 'k') weak |= LJ_GC_WEAKKEY;
170 else if (c == 'v') weak |= LJ_GC_WEAKVAL;
171 else if (c == 'K') weak = (int)(~0u & ~LJ_GC_WEAKVAL);
172 }
173 if (weak > 0) { /* Weak tables are cleared in the atomic phase. */
174 t->marked = (uint8_t)((t->marked & ~LJ_GC_WEAK) | weak);
175 setgcrefr(t->gclist, g->gc.weak);
176 setgcref(g->gc.weak, obj2gco(t));
177 }
178 }
179 if (weak == LJ_GC_WEAK) /* Nothing to mark if both keys/values are weak. */
180 return 1;
181 if (!(weak & LJ_GC_WEAKVAL)) { /* Mark array part. */
182 MSize i, asize = t->asize;
183 for (i = 0; i < asize; i++)
184 gc_marktv(g, arrayslot(t, i));
185 }
186 if (t->hmask > 0) { /* Mark hash part. */
187 Node *node = noderef(t->node);
188 MSize i, hmask = t->hmask;
189 for (i = 0; i <= hmask; i++) {
190 Node *n = &node[i];
191 if (!tvisnil(&n->val)) { /* Mark non-empty slot. */
192 lua_assert(!tvisnil(&n->key));
193 if (!(weak & LJ_GC_WEAKKEY)) gc_marktv(g, &n->key);
194 if (!(weak & LJ_GC_WEAKVAL)) gc_marktv(g, &n->val);
195 }
196 }
197 }
198 return weak;
199}
200
201/* Traverse a function. */
202static void gc_traverse_func(global_State *g, GCfunc *fn)
203{
204 gc_markobj(g, tabref(fn->c.env));
205 if (isluafunc(fn)) {
206 uint32_t i;
207 lua_assert(fn->l.nupvalues <= funcproto(fn)->sizeuv);
208 gc_markobj(g, funcproto(fn));
209 for (i = 0; i < fn->l.nupvalues; i++) /* Mark Lua function upvalues. */
210 gc_markobj(g, &gcref(fn->l.uvptr[i])->uv);
211 } else {
212 uint32_t i;
213 for (i = 0; i < fn->c.nupvalues; i++) /* Mark C function upvalues. */
214 gc_marktv(g, &fn->c.upvalue[i]);
215 }
216}
217
218#if LJ_HASJIT
219/* Mark a trace. */
220static void gc_marktrace(global_State *g, TraceNo traceno)
221{
222 GCobj *o = obj2gco(traceref(G2J(g), traceno));
223 lua_assert(traceno != G2J(g)->cur.traceno);
224 if (iswhite(o)) {
225 white2gray(o);
226 setgcrefr(o->gch.gclist, g->gc.gray);
227 setgcref(g->gc.gray, o);
228 }
229}
230
231/* Traverse a trace. */
232static void gc_traverse_trace(global_State *g, GCtrace *T)
233{
234 IRRef ref;
235 if (T->traceno == 0) return;
236 for (ref = T->nk; ref < REF_TRUE; ref++) {
237 IRIns *ir = &T->ir[ref];
238 if (ir->o == IR_KGC)
239 gc_markobj(g, ir_kgc(ir));
240 }
241 if (T->link) gc_marktrace(g, T->link);
242 if (T->nextroot) gc_marktrace(g, T->nextroot);
243 if (T->nextside) gc_marktrace(g, T->nextside);
244 gc_markobj(g, gcref(T->startpt));
245}
246
247/* The current trace is a GC root while not anchored in the prototype (yet). */
248#define gc_traverse_curtrace(g) gc_traverse_trace(g, &G2J(g)->cur)
249#else
250#define gc_traverse_curtrace(g) UNUSED(g)
251#endif
252
253/* Traverse a prototype. */
254static void gc_traverse_proto(global_State *g, GCproto *pt)
255{
256 ptrdiff_t i;
257 gc_mark_str(proto_chunkname(pt));
258 for (i = -(ptrdiff_t)pt->sizekgc; i < 0; i++) /* Mark collectable consts. */
259 gc_markobj(g, proto_kgc(pt, i));
260#if LJ_HASJIT
261 if (pt->trace) gc_marktrace(g, pt->trace);
262#endif
263}
264
265/* Traverse the frame structure of a stack. */
266static MSize gc_traverse_frames(global_State *g, lua_State *th)
267{
268 TValue *frame, *top = th->top-1, *bot = tvref(th->stack);
269 /* Note: extra vararg frame not skipped, marks function twice (harmless). */
270 for (frame = th->base-1; frame > bot; frame = frame_prev(frame)) {
271 GCfunc *fn = frame_func(frame);
272 TValue *ftop = frame;
273 if (isluafunc(fn)) ftop += funcproto(fn)->framesize;
274 if (ftop > top) top = ftop;
275 gc_markobj(g, fn); /* Need to mark hidden function (or L). */
276 }
277 top++; /* Correct bias of -1 (frame == base-1). */
278 if (top > tvref(th->maxstack)) top = tvref(th->maxstack);
279 return (MSize)(top - bot); /* Return minimum needed stack size. */
280}
281
282/* Traverse a thread object. */
283static void gc_traverse_thread(global_State *g, lua_State *th)
284{
285 TValue *o, *top = th->top;
286 for (o = tvref(th->stack)+1; o < top; o++)
287 gc_marktv(g, o);
288 if (g->gc.state == GCSatomic) {
289 top = tvref(th->stack) + th->stacksize;
290 for (; o < top; o++) /* Clear unmarked slots. */
291 setnilV(o);
292 }
293 gc_markobj(g, tabref(th->env));
294 lj_state_shrinkstack(th, gc_traverse_frames(g, th));
295}
296
297/* Propagate one gray object. Traverse it and turn it black. */
298static size_t propagatemark(global_State *g)
299{
300 GCobj *o = gcref(g->gc.gray);
301 int gct = o->gch.gct;
302 lua_assert(isgray(o));
303 gray2black(o);
304 setgcrefr(g->gc.gray, o->gch.gclist); /* Remove from gray list. */
305 if (LJ_LIKELY(gct == ~LJ_TTAB)) {
306 GCtab *t = gco2tab(o);
307 if (gc_traverse_tab(g, t) > 0)
308 black2gray(o); /* Keep weak tables gray. */
309 return sizeof(GCtab) + sizeof(TValue) * t->asize +
310 sizeof(Node) * (t->hmask + 1);
311 } else if (LJ_LIKELY(gct == ~LJ_TFUNC)) {
312 GCfunc *fn = gco2func(o);
313 gc_traverse_func(g, fn);
314 return isluafunc(fn) ? sizeLfunc((MSize)fn->l.nupvalues) :
315 sizeCfunc((MSize)fn->c.nupvalues);
316 } else if (LJ_LIKELY(gct == ~LJ_TPROTO)) {
317 GCproto *pt = gco2pt(o);
318 gc_traverse_proto(g, pt);
319 return pt->sizept;
320 } else if (LJ_LIKELY(gct == ~LJ_TTHREAD)) {
321 lua_State *th = gco2th(o);
322 setgcrefr(th->gclist, g->gc.grayagain);
323 setgcref(g->gc.grayagain, o);
324 black2gray(o); /* Threads are never black. */
325 gc_traverse_thread(g, th);
326 return sizeof(lua_State) + sizeof(TValue) * th->stacksize;
327 } else {
328#if LJ_HASJIT
329 GCtrace *T = gco2trace(o);
330 gc_traverse_trace(g, T);
331 return ((sizeof(GCtrace)+7)&~7) + (T->nins-T->nk)*sizeof(IRIns) +
332 T->nsnap*sizeof(SnapShot) + T->nsnapmap*sizeof(SnapEntry);
333#else
334 lua_assert(0);
335 return 0;
336#endif
337 }
338}
339
340/* Propagate all gray objects. */
341static size_t gc_propagate_gray(global_State *g)
342{
343 size_t m = 0;
344 while (gcref(g->gc.gray) != NULL)
345 m += propagatemark(g);
346 return m;
347}
348
349/* -- Sweep phase --------------------------------------------------------- */
350
351/* Try to shrink some common data structures. */
352static void gc_shrink(global_State *g, lua_State *L)
353{
354 if (g->strnum <= (g->strmask >> 2) && g->strmask > LJ_MIN_STRTAB*2-1)
355 lj_str_resize(L, g->strmask >> 1); /* Shrink string table. */
356 if (g->tmpbuf.sz > LJ_MIN_SBUF*2)
357 lj_str_resizebuf(L, &g->tmpbuf, g->tmpbuf.sz >> 1); /* Shrink temp buf. */
358}
359
360/* Type of GC free functions. */
361typedef void (LJ_FASTCALL *GCFreeFunc)(global_State *g, GCobj *o);
362
363/* GC free functions for LJ_TSTR .. LJ_TUDATA. ORDER LJ_T */
364static const GCFreeFunc gc_freefunc[] = {
365 (GCFreeFunc)lj_str_free,
366 (GCFreeFunc)lj_func_freeuv,
367 (GCFreeFunc)lj_state_free,
368 (GCFreeFunc)lj_func_freeproto,
369 (GCFreeFunc)lj_func_free,
370#if LJ_HASJIT
371 (GCFreeFunc)lj_trace_free,
372#else
373 (GCFreeFunc)0,
374#endif
375#if LJ_HASFFI
376 (GCFreeFunc)lj_cdata_free,
377#else
378 (GCFreeFunc)0,
379#endif
380 (GCFreeFunc)lj_tab_free,
381 (GCFreeFunc)lj_udata_free
382};
383
384/* Full sweep of a GC list. */
385#define gc_fullsweep(g, p) gc_sweep(g, (p), LJ_MAX_MEM)
386
387/* Partial sweep of a GC list. */
388static GCRef *gc_sweep(global_State *g, GCRef *p, uint32_t lim)
389{
390 /* Mask with other white and LJ_GC_FIXED. Or LJ_GC_SFIXED on shutdown. */
391 int ow = otherwhite(g);
392 GCobj *o;
393 while ((o = gcref(*p)) != NULL && lim-- > 0) {
394 if (o->gch.gct == ~LJ_TTHREAD) /* Need to sweep open upvalues, too. */
395 gc_fullsweep(g, &gco2th(o)->openupval);
396 if (((o->gch.marked ^ LJ_GC_WHITES) & ow)) { /* Black or current white? */
397 lua_assert(!isdead(g, o) || (o->gch.marked & LJ_GC_FIXED));
398 makewhite(g, o); /* Value is alive, change to the current white. */
399 p = &o->gch.nextgc;
400 } else { /* Otherwise value is dead, free it. */
401 lua_assert(isdead(g, o) || ow == LJ_GC_SFIXED);
402 setgcrefr(*p, o->gch.nextgc);
403 if (o == gcref(g->gc.root))
404 setgcrefr(g->gc.root, o->gch.nextgc); /* Adjust list anchor. */
405 gc_freefunc[o->gch.gct - ~LJ_TSTR](g, o);
406 }
407 }
408 return p;
409}
410
411/* Check whether we can clear a key or a value slot from a table. */
412static int gc_mayclear(cTValue *o, int val)
413{
414 if (tvisgcv(o)) { /* Only collectable objects can be weak references. */
415 if (tvisstr(o)) { /* But strings cannot be used as weak references. */
416 gc_mark_str(strV(o)); /* And need to be marked. */
417 return 0;
418 }
419 if (iswhite(gcV(o)))
420 return 1; /* Object is about to be collected. */
421 if (tvisudata(o) && val && isfinalized(udataV(o)))
422 return 1; /* Finalized userdata is dropped only from values. */
423 }
424 return 0; /* Cannot clear. */
425}
426
427/* Clear collected entries from weak tables. */
428static void gc_clearweak(GCobj *o)
429{
430 while (o) {
431 GCtab *t = gco2tab(o);
432 lua_assert((t->marked & LJ_GC_WEAK));
433 if ((t->marked & LJ_GC_WEAKVAL)) {
434 MSize i, asize = t->asize;
435 for (i = 0; i < asize; i++) {
436 /* Clear array slot when value is about to be collected. */
437 TValue *tv = arrayslot(t, i);
438 if (gc_mayclear(tv, 1))
439 setnilV(tv);
440 }
441 }
442 if (t->hmask > 0) {
443 Node *node = noderef(t->node);
444 MSize i, hmask = t->hmask;
445 for (i = 0; i <= hmask; i++) {
446 Node *n = &node[i];
447 /* Clear hash slot when key or value is about to be collected. */
448 if (!tvisnil(&n->val) && (gc_mayclear(&n->key, 0) ||
449 gc_mayclear(&n->val, 1)))
450 setnilV(&n->val);
451 }
452 }
453 o = gcref(t->gclist);
454 }
455}
456
457/* Call a userdata or cdata finalizer. */
458static void gc_call_finalizer(global_State *g, lua_State *L,
459 cTValue *mo, GCobj *o)
460{
461 /* Save and restore lots of state around the __gc callback. */
462 uint8_t oldh = hook_save(g);
463 MSize oldt = g->gc.threshold;
464 int errcode;
465 TValue *top;
466 lj_trace_abort(g);
467 top = L->top;
468 L->top = top+2;
469 hook_entergc(g); /* Disable hooks and new traces during __gc. */
470 g->gc.threshold = LJ_MAX_MEM; /* Prevent GC steps. */
471 copyTV(L, top, mo);
472 setgcV(L, top+1, o, ~o->gch.gct);
473 errcode = lj_vm_pcall(L, top+1, 1+0, -1); /* Stack: |mo|o| -> | */
474 hook_restore(g, oldh);
475 g->gc.threshold = oldt; /* Restore GC threshold. */
476 if (errcode)
477 lj_err_throw(L, errcode); /* Propagate errors. */
478}
479
480/* Finalize one userdata or cdata object from the mmudata list. */
481static void gc_finalize(lua_State *L)
482{
483 global_State *g = G(L);
484 GCobj *o = gcnext(gcref(g->gc.mmudata));
485 cTValue *mo;
486 lua_assert(gcref(g->jit_L) == NULL); /* Must not be called on trace. */
487 /* Unchain from list of userdata to be finalized. */
488 if (o == gcref(g->gc.mmudata))
489 setgcrefnull(g->gc.mmudata);
490 else
491 setgcrefr(gcref(g->gc.mmudata)->gch.nextgc, o->gch.nextgc);
492#if LJ_HASFFI
493 if (o->gch.gct == ~LJ_TCDATA) {
494 TValue tmp, *tv;
495 /* Add cdata back to the GC list and make it white. */
496 setgcrefr(o->gch.nextgc, g->gc.root);
497 setgcref(g->gc.root, o);
498 makewhite(g, o);
499 o->gch.marked &= (uint8_t)~LJ_GC_CDATA_FIN;
500 /* Resolve finalizer. */
501 setcdataV(L, &tmp, gco2cd(o));
502 tv = lj_tab_set(L, ctype_ctsG(g)->finalizer, &tmp);
503 if (!tvisnil(tv)) {
504 g->gc.nocdatafin = 0;
505 copyTV(L, &tmp, tv);
506 setnilV(tv); /* Clear entry in finalizer table. */
507 gc_call_finalizer(g, L, &tmp, o);
508 }
509 return;
510 }
511#endif
512 /* Add userdata back to the main userdata list and make it white. */
513 setgcrefr(o->gch.nextgc, mainthread(g)->nextgc);
514 setgcref(mainthread(g)->nextgc, o);
515 makewhite(g, o);
516 /* Resolve the __gc metamethod. */
517 mo = lj_meta_fastg(g, tabref(gco2ud(o)->metatable), MM_gc);
518 if (mo)
519 gc_call_finalizer(g, L, mo, o);
520}
521
522/* Finalize all userdata objects from mmudata list. */
523void lj_gc_finalize_udata(lua_State *L)
524{
525 while (gcref(G(L)->gc.mmudata) != NULL)
526 gc_finalize(L);
527}
528
529#if LJ_HASFFI
530/* Finalize all cdata objects from finalizer table. */
531void lj_gc_finalize_cdata(lua_State *L)
532{
533 global_State *g = G(L);
534 CTState *cts = ctype_ctsG(g);
535 if (cts) {
536 GCtab *t = cts->finalizer;
537 Node *node = noderef(t->node);
538 ptrdiff_t i;
539 setgcrefnull(t->metatable); /* Mark finalizer table as disabled. */
540 for (i = (ptrdiff_t)t->hmask; i >= 0; i--)
541 if (!tvisnil(&node[i].val) && tviscdata(&node[i].key)) {
542 GCobj *o = gcV(&node[i].key);
543 TValue tmp;
544 makewhite(g, o);
545 o->gch.marked &= (uint8_t)~LJ_GC_CDATA_FIN;
546 copyTV(L, &tmp, &node[i].val);
547 setnilV(&node[i].val);
548 gc_call_finalizer(g, L, &tmp, o);
549 }
550 }
551}
552#endif
553
554/* Free all remaining GC objects. */
555void lj_gc_freeall(global_State *g)
556{
557 MSize i, strmask;
558 /* Free everything, except super-fixed objects (the main thread). */
559 g->gc.currentwhite = LJ_GC_WHITES | LJ_GC_SFIXED;
560 gc_fullsweep(g, &g->gc.root);
561 strmask = g->strmask;
562 for (i = 0; i <= strmask; i++) /* Free all string hash chains. */
563 gc_fullsweep(g, &g->strhash[i]);
564}
565
566/* -- Collector ----------------------------------------------------------- */
567
568/* Atomic part of the GC cycle, transitioning from mark to sweep phase. */
569static void atomic(global_State *g, lua_State *L)
570{
571 size_t udsize;
572
573 gc_mark_uv(g); /* Need to remark open upvalues (the thread may be dead). */
574 gc_propagate_gray(g); /* Propagate any left-overs. */
575
576 setgcrefr(g->gc.gray, g->gc.weak); /* Empty the list of weak tables. */
577 setgcrefnull(g->gc.weak);
578 lua_assert(!iswhite(obj2gco(mainthread(g))));
579 gc_markobj(g, L); /* Mark running thread. */
580 gc_traverse_curtrace(g); /* Traverse current trace. */
581 gc_mark_gcroot(g); /* Mark GC roots (again). */
582 gc_propagate_gray(g); /* Propagate all of the above. */
583
584 setgcrefr(g->gc.gray, g->gc.grayagain); /* Empty the 2nd chance list. */
585 setgcrefnull(g->gc.grayagain);
586 gc_propagate_gray(g); /* Propagate it. */
587
588 udsize = lj_gc_separateudata(g, 0); /* Separate userdata to be finalized. */
589 gc_mark_mmudata(g); /* Mark them. */
590 udsize += gc_propagate_gray(g); /* And propagate the marks. */
591
592 /* All marking done, clear weak tables. */
593 gc_clearweak(gcref(g->gc.weak));
594
595 /* Prepare for sweep phase. */
596 g->gc.currentwhite = (uint8_t)otherwhite(g); /* Flip current white. */
597 g->strempty.marked = g->gc.currentwhite;
598 setmref(g->gc.sweep, &g->gc.root);
599 g->gc.estimate = g->gc.total - (MSize)udsize; /* Initial estimate. */
600}
601
602/* GC state machine. Returns a cost estimate for each step performed. */
603static size_t gc_onestep(lua_State *L)
604{
605 global_State *g = G(L);
606 switch (g->gc.state) {
607 case GCSpause:
608 gc_mark_start(g); /* Start a new GC cycle by marking all GC roots. */
609 return 0;
610 case GCSpropagate:
611 if (gcref(g->gc.gray) != NULL)
612 return propagatemark(g); /* Propagate one gray object. */
613 g->gc.state = GCSatomic; /* End of mark phase. */
614 return 0;
615 case GCSatomic:
616 if (gcref(g->jit_L)) /* Don't run atomic phase on trace. */
617 return LJ_MAX_MEM;
618 atomic(g, L);
619 g->gc.state = GCSsweepstring; /* Start of sweep phase. */
620 g->gc.sweepstr = 0;
621 return 0;
622 case GCSsweepstring: {
623 MSize old = g->gc.total;
624 gc_fullsweep(g, &g->strhash[g->gc.sweepstr++]); /* Sweep one chain. */
625 if (g->gc.sweepstr > g->strmask)
626 g->gc.state = GCSsweep; /* All string hash chains sweeped. */
627 lua_assert(old >= g->gc.total);
628 g->gc.estimate -= old - g->gc.total;
629 return GCSWEEPCOST;
630 }
631 case GCSsweep: {
632 MSize old = g->gc.total;
633 setmref(g->gc.sweep, gc_sweep(g, mref(g->gc.sweep, GCRef), GCSWEEPMAX));
634 if (gcref(*mref(g->gc.sweep, GCRef)) == NULL) {
635 gc_shrink(g, L);
636 if (gcref(g->gc.mmudata)) { /* Need any finalizations? */
637 g->gc.state = GCSfinalize;
638#if LJ_HASFFI
639 g->gc.nocdatafin = 1;
640#endif
641 } else { /* Otherwise skip this phase to help the JIT. */
642 g->gc.state = GCSpause; /* End of GC cycle. */
643 g->gc.debt = 0;
644 }
645 }
646 lua_assert(old >= g->gc.total);
647 g->gc.estimate -= old - g->gc.total;
648 return GCSWEEPMAX*GCSWEEPCOST;
649 }
650 case GCSfinalize:
651 if (gcref(g->gc.mmudata) != NULL) {
652 if (gcref(g->jit_L)) /* Don't call finalizers on trace. */
653 return LJ_MAX_MEM;
654 gc_finalize(L); /* Finalize one userdata object. */
655 if (g->gc.estimate > GCFINALIZECOST)
656 g->gc.estimate -= GCFINALIZECOST;
657 return GCFINALIZECOST;
658 }
659#if LJ_HASFFI
660 if (!g->gc.nocdatafin) lj_tab_rehash(L, ctype_ctsG(g)->finalizer);
661#endif
662 g->gc.state = GCSpause; /* End of GC cycle. */
663 g->gc.debt = 0;
664 return 0;
665 default:
666 lua_assert(0);
667 return 0;
668 }
669}
670
671/* Perform a limited amount of incremental GC steps. */
672int LJ_FASTCALL lj_gc_step(lua_State *L)
673{
674 global_State *g = G(L);
675 MSize lim;
676 int32_t ostate = g->vmstate;
677 setvmstate(g, GC);
678 lim = (GCSTEPSIZE/100) * g->gc.stepmul;
679 if (lim == 0)
680 lim = LJ_MAX_MEM;
681 if (g->gc.total > g->gc.threshold)
682 g->gc.debt += g->gc.total - g->gc.threshold;
683 do {
684 lim -= (MSize)gc_onestep(L);
685 if (g->gc.state == GCSpause) {
686 g->gc.threshold = (g->gc.estimate/100) * g->gc.pause;
687 g->vmstate = ostate;
688 return 1; /* Finished a GC cycle. */
689 }
690 } while ((int32_t)lim > 0);
691 if (g->gc.debt < GCSTEPSIZE) {
692 g->gc.threshold = g->gc.total + GCSTEPSIZE;
693 g->vmstate = ostate;
694 return -1;
695 } else {
696 g->gc.debt -= GCSTEPSIZE;
697 g->gc.threshold = g->gc.total;
698 g->vmstate = ostate;
699 return 0;
700 }
701}
702
703/* Ditto, but fix the stack top first. */
704void LJ_FASTCALL lj_gc_step_fixtop(lua_State *L)
705{
706 if (curr_funcisL(L)) L->top = curr_topL(L);
707 lj_gc_step(L);
708}
709
710#if LJ_HASJIT
711/* Perform multiple GC steps. Called from JIT-compiled code. */
712int LJ_FASTCALL lj_gc_step_jit(global_State *g, MSize steps)
713{
714 lua_State *L = gco2th(gcref(g->jit_L));
715 L->base = mref(G(L)->jit_base, TValue);
716 L->top = curr_topL(L);
717 while (steps-- > 0 && lj_gc_step(L) == 0)
718 ;
719 /* Return 1 to force a trace exit. */
720 return (G(L)->gc.state == GCSatomic || G(L)->gc.state == GCSfinalize);
721}
722#endif
723
724/* Perform a full GC cycle. */
725void lj_gc_fullgc(lua_State *L)
726{
727 global_State *g = G(L);
728 int32_t ostate = g->vmstate;
729 setvmstate(g, GC);
730 if (g->gc.state <= GCSatomic) { /* Caught somewhere in the middle. */
731 setmref(g->gc.sweep, &g->gc.root); /* Sweep everything (preserving it). */
732 setgcrefnull(g->gc.gray); /* Reset lists from partial propagation. */
733 setgcrefnull(g->gc.grayagain);
734 setgcrefnull(g->gc.weak);
735 g->gc.state = GCSsweepstring; /* Fast forward to the sweep phase. */
736 g->gc.sweepstr = 0;
737 }
738 while (g->gc.state == GCSsweepstring || g->gc.state == GCSsweep)
739 gc_onestep(L); /* Finish sweep. */
740 lua_assert(g->gc.state == GCSfinalize || g->gc.state == GCSpause);
741 /* Now perform a full GC. */
742 g->gc.state = GCSpause;
743 do { gc_onestep(L); } while (g->gc.state != GCSpause);
744 g->gc.threshold = (g->gc.estimate/100) * g->gc.pause;
745 g->vmstate = ostate;
746}
747
748/* -- Write barriers ------------------------------------------------------ */
749
750/* Move the GC propagation frontier forward. */
751void lj_gc_barrierf(global_State *g, GCobj *o, GCobj *v)
752{
753 lua_assert(isblack(o) && iswhite(v) && !isdead(g, v) && !isdead(g, o));
754 lua_assert(g->gc.state != GCSfinalize && g->gc.state != GCSpause);
755 lua_assert(o->gch.gct != ~LJ_TTAB);
756 /* Preserve invariant during propagation. Otherwise it doesn't matter. */
757 if (g->gc.state == GCSpropagate || g->gc.state == GCSatomic)
758 gc_mark(g, v); /* Move frontier forward. */
759 else
760 makewhite(g, o); /* Make it white to avoid the following barrier. */
761}
762
763/* Specialized barrier for closed upvalue. Pass &uv->tv. */
764void LJ_FASTCALL lj_gc_barrieruv(global_State *g, TValue *tv)
765{
766#define TV2MARKED(x) \
767 (*((uint8_t *)(x) - offsetof(GCupval, tv) + offsetof(GCupval, marked)))
768 if (g->gc.state == GCSpropagate || g->gc.state == GCSatomic)
769 gc_mark(g, gcV(tv));
770 else
771 TV2MARKED(tv) = (TV2MARKED(tv) & (uint8_t)~LJ_GC_COLORS) | curwhite(g);
772#undef TV2MARKED
773}
774
775/* Close upvalue. Also needs a write barrier. */
776void lj_gc_closeuv(global_State *g, GCupval *uv)
777{
778 GCobj *o = obj2gco(uv);
779 /* Copy stack slot to upvalue itself and point to the copy. */
780 copyTV(mainthread(g), &uv->tv, uvval(uv));
781 setmref(uv->v, &uv->tv);
782 uv->closed = 1;
783 setgcrefr(o->gch.nextgc, g->gc.root);
784 setgcref(g->gc.root, o);
785 if (isgray(o)) { /* A closed upvalue is never gray, so fix this. */
786 if (g->gc.state == GCSpropagate || g->gc.state == GCSatomic) {
787 gray2black(o); /* Make it black and preserve invariant. */
788 if (tviswhite(&uv->tv))
789 lj_gc_barrierf(g, o, gcV(&uv->tv));
790 } else {
791 makewhite(g, o); /* Make it white, i.e. sweep the upvalue. */
792 lua_assert(g->gc.state != GCSfinalize && g->gc.state != GCSpause);
793 }
794 }
795}
796
797#if LJ_HASJIT
798/* Mark a trace if it's saved during the propagation phase. */
799void lj_gc_barriertrace(global_State *g, uint32_t traceno)
800{
801 if (g->gc.state == GCSpropagate || g->gc.state == GCSatomic)
802 gc_marktrace(g, traceno);
803}
804#endif
805
806/* -- Allocator ----------------------------------------------------------- */
807
808/* Call pluggable memory allocator to allocate or resize a fragment. */
809void *lj_mem_realloc(lua_State *L, void *p, MSize osz, MSize nsz)
810{
811 global_State *g = G(L);
812 lua_assert((osz == 0) == (p == NULL));
813 p = g->allocf(g->allocd, p, osz, nsz);
814 if (p == NULL && nsz > 0)
815 lj_err_mem(L);
816 lua_assert((nsz == 0) == (p == NULL));
817 lua_assert(checkptr32(p));
818 g->gc.total = (g->gc.total - osz) + nsz;
819 return p;
820}
821
822/* Allocate new GC object and link it to the root set. */
823void * LJ_FASTCALL lj_mem_newgco(lua_State *L, MSize size)
824{
825 global_State *g = G(L);
826 GCobj *o = (GCobj *)g->allocf(g->allocd, NULL, 0, size);
827 if (o == NULL)
828 lj_err_mem(L);
829 lua_assert(checkptr32(o));
830 g->gc.total += size;
831 setgcrefr(o->gch.nextgc, g->gc.root);
832 setgcref(g->gc.root, o);
833 newwhite(g, o);
834 return o;
835}
836
837/* Resize growable vector. */
838void *lj_mem_grow(lua_State *L, void *p, MSize *szp, MSize lim, MSize esz)
839{
840 MSize sz = (*szp) << 1;
841 if (sz < LJ_MIN_VECSZ)
842 sz = LJ_MIN_VECSZ;
843 if (sz > lim)
844 sz = lim;
845 p = lj_mem_realloc(L, p, (*szp)*esz, sz*esz);
846 *szp = sz;
847 return p;
848}
849
850