GCC Code Coverage Report

Directory: ./
File: firmware/ext/lua/lgc.c
Date: 2025-10-24 14:26:41
Warnings: 3 unchecked decisions!
Coverage Exec Excl Total
Lines: 55.7% 433 0 778
Functions: 68.5% 50 0 73
Branches: 34.5% 162 0 470
Decisions: 36.9% 108 - 293
Line Branch Decision Exec Source
1 /*
2 ** $Id: lgc.c $
3 ** Garbage Collector
4 ** See Copyright Notice in lua.h
5 */
6
7 #define lgc_c
8 #define LUA_CORE
9
10 #include "lprefix.h"
11
12 #include <stdio.h>
13 #include <string.h>
14
15
16 #include "lua.h"
17
18 #include "ldebug.h"
19 #include "ldo.h"
20 #include "lfunc.h"
21 #include "lgc.h"
22 #include "lmem.h"
23 #include "lobject.h"
24 #include "lstate.h"
25 #include "lstring.h"
26 #include "ltable.h"
27 #include "ltm.h"
28
29
30 /*
31 ** Maximum number of elements to sweep in each single step.
32 ** (Large enough to dissipate fixed overheads but small enough
33 ** to allow small steps for the collector.)
34 */
35 #define GCSWEEPMAX 100
36
37 /*
38 ** Maximum number of finalizers to call in each single step.
39 */
40 #define GCFINMAX 10
41
42
43 /*
44 ** Cost of calling one finalizer.
45 */
46 #define GCFINALIZECOST 50
47
48
49 /*
50 ** The equivalent, in bytes, of one unit of "work" (visiting a slot,
51 ** sweeping an object, etc.)
52 */
53 #define WORK2MEM sizeof(TValue)
54
55
56 /*
57 ** macro to adjust 'pause': 'pause' is actually used like
58 ** 'pause / PAUSEADJ' (value chosen by tests)
59 */
60 #define PAUSEADJ 100
61
62
63 /* mask with all color bits */
64 #define maskcolors (bitmask(BLACKBIT) | WHITEBITS)
65
66 /* mask with all GC bits */
67 #define maskgcbits (maskcolors | AGEBITS)
68
69
70 /* macro to erase all color bits then set only the current white bit */
71 #define makewhite(g,x) \
72 (x->marked = cast_byte((x->marked & ~maskcolors) | luaC_white(g)))
73
74 /* make an object gray (neither white nor black) */
75 #define set2gray(x) resetbits(x->marked, maskcolors)
76
77
78 /* make an object black (coming from any color) */
79 #define set2black(x) \
80 (x->marked = cast_byte((x->marked & ~WHITEBITS) | bitmask(BLACKBIT)))
81
82
83 #define valiswhite(x) (iscollectable(x) && iswhite(gcvalue(x)))
84
85 #define keyiswhite(n) (keyiscollectable(n) && iswhite(gckey(n)))
86
87
88 /*
89 ** Protected access to objects in values
90 */
91 #define gcvalueN(o) (iscollectable(o) ? gcvalue(o) : NULL)
92
93
94 #define markvalue(g,o) { checkliveness(g->mainthread,o); \
95 if (valiswhite(o)) reallymarkobject(g,gcvalue(o)); }
96
97 #define markkey(g, n) { if keyiswhite(n) reallymarkobject(g,gckey(n)); }
98
99 #define markobject(g,t) { if (iswhite(t)) reallymarkobject(g, obj2gco(t)); }
100
101 /*
102 ** mark an object that can be NULL (either because it is really optional,
103 ** or it was stripped as debug info, or inside an uncompleted structure)
104 */
105 #define markobjectN(g,t) { if (t) markobject(g,t); }
106
107 static void reallymarkobject (global_State *g, GCObject *o);
108 static lu_mem atomic (lua_State *L);
109 static void entersweep (lua_State *L);
110
111
112 /*
113 ** {======================================================
114 ** Generic functions
115 ** =======================================================
116 */
117
118
119 /*
120 ** one after last element in a hash array
121 */
122 #define gnodelast(h) gnode(h, cast_sizet(sizenode(h)))
123
124
125 61479 static GCObject **getgclist (GCObject *o) {
126
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 61479 switch (o->tt) {
127
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 22572 case LUA_VTABLE: return &gco2t(o)->gclist;
128 ✗ case LUA_VLCL: return &gco2lcl(o)->gclist;
129
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 16632 case LUA_VCCL: return &gco2ccl(o)->gclist;
130
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 2673 case LUA_VTHREAD: return &gco2th(o)->gclist;
131 ✗ case LUA_VPROTO: return &gco2p(o)->gclist;
132
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 19602 case LUA_VUSERDATA: {
133 19602 Udata *u = gco2u(o);
134 lua_assert(u->nuvalue > 0);
135 19602 return &u->gclist;
136 }
137 ✗ default: lua_assert(0); return 0;
138 }
139 }
140
141
142 /*
143 ** Link a collectable object 'o' with a known type into the list 'p'.
144 ** (Must be a macro to access the 'gclist' field in different types.)
145 */
146 #define linkgclist(o,p) linkgclist_(obj2gco(o), &(o)->gclist, &(p))
147
148 31185 static void linkgclist_ (GCObject *o, GCObject **pnext, GCObject **list) {
149 lua_assert(!isgray(o)); /* cannot be in a gray list */
150 31185 *pnext = *list;
151 31185 *list = o;
152 31185 set2gray(o); /* now it is */
153 31185 }
154
155
156 /*
157 ** Link a generic collectable object 'o' into the list 'p'.
158 */
159 #define linkobjgclist(o,p) linkgclist_(obj2gco(o), getgclist(o), &(p))
160
161
162
163 /*
164 ** Clear keys for empty entries in tables. If entry is empty, mark its
165 ** entry as dead. This allows the collection of the key, but keeps its
166 ** entry in the table: its removal could break a chain and could break
167 ** a table traversal. Other places never manipulate dead keys, because
168 ** its associated empty value is enough to signal that the entry is
169 ** logically empty.
170 */
171 10989 static void clearkey (Node *n) {
172 lua_assert(isempty(gval(n)));
173
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 10989 if (keyiscollectable(n))
174 ✗ setdeadkey(n); /* unused key; remove it */
175 10989 }
176
177
178 /*
179 ** tells whether a key or value can be cleared from a weak
180 ** table. Non-collectable objects are never removed from weak
181 ** tables. Strings behave as 'values', so are never removed too. for
182 ** other objects: if really collected, cannot keep them; for objects
183 ** being finalized, keep them in keys, but not in values
184 */
185 ✗ static int iscleared (global_State *g, const GCObject *o) {
186 ✗ if (o == NULL) return 0; /* non-collectable value */
187 ✗ else if (novariant(o->tt) == LUA_TSTRING) {
188 ✗ markobject(g, o); /* strings are 'values', so are never weak */
189 ✗ return 0;
190 }
191 ✗ else return iswhite(o);
192 }
193
194
195 /*
196 ** Barrier that moves collector forward, that is, marks the white object
197 ** 'v' being pointed by the black object 'o'. In the generational
198 ** mode, 'v' must also become old, if 'o' is old; however, it cannot
199 ** be changed directly to OLD, because it may still point to non-old
200 ** objects. So, it is marked as OLD0. In the next cycle it will become
201 ** OLD1, and in the next it will finally become OLD (regular old). By
202 ** then, any object it points to will also be old. If called in the
203 ** incremental sweep phase, it clears the black object to white (sweep
204 ** it) to avoid other barrier calls for this same object. (That cannot
205 ** be done is generational mode, as its sweep does not distinguish
206 ** whites from deads.)
207 */
208 ✗ void luaC_barrier_ (lua_State *L, GCObject *o, GCObject *v) {
209 ✗ global_State *g = G(L);
210 lua_assert(isblack(o) && iswhite(v) && !isdead(g, v) && !isdead(g, o));
211 ✗ if (keepinvariant(g)) { /* must keep invariant? */
212 ✗ reallymarkobject(g, v); /* restore invariant */
213 ✗ if (isold(o)) {
214 lua_assert(!isold(v)); /* white object could not be old */
215 ✗ setage(v, G_OLD0); /* restore generational invariant */
216 }
217 }
218 else { /* sweep phase */
219 lua_assert(issweepphase(g));
220 ✗ if (g->gckind == KGC_INC) /* incremental mode? */
221 ✗ makewhite(g, o); /* mark 'o' as white to avoid other barriers */
222 }
223 ✗ }
224
225
226 /*
227 ** barrier that moves collector backward, that is, mark the black object
228 ** pointing to a white object as gray again.
229 */
230 ✗ void luaC_barrierback_ (lua_State *L, GCObject *o) {
231 ✗ global_State *g = G(L);
232 lua_assert(isblack(o) && !isdead(g, o));
233 lua_assert((g->gckind == KGC_GEN) == (isold(o) && getage(o) != G_TOUCHED1));
234 ✗ if (getage(o) == G_TOUCHED2) /* already in gray list? */
235 ✗ set2gray(o); /* make it gray to become touched1 */
236 else /* link it in 'grayagain' and paint it gray */
237 ✗ linkobjgclist(o, g->grayagain);
238 ✗ if (isold(o)) /* generational mode? */
239 ✗ setage(o, G_TOUCHED1); /* touched in current cycle */
240 ✗ }
241
242
243 14553 void luaC_fix (lua_State *L, GCObject *o) {
244 14553 global_State *g = G(L);
245 lua_assert(g->allgc == o); /* object must be 1st in 'allgc' list! */
246 14553 set2gray(o); /* they will be gray forever */
247 14553 setage(o, G_OLD); /* and old forever */
248 14553 g->allgc = o->next; /* remove object from 'allgc' list */
249 14553 o->next = g->fixedgc; /* link it to 'fixedgc' list */
250 14553 g->fixedgc = o;
251 14553 }
252
253
254 /*
255 ** create a new collectable object (with given type, size, and offset)
256 ** and link it to 'allgc' list.
257 */
258 70922 GCObject *luaC_newobjdt (lua_State *L, int tt, size_t sz, size_t offset) {
259 70922 global_State *g = G(L);
260 70922 char *p = cast_charp(luaM_newobject(L, novariant(tt), sz));
261 70922 GCObject *o = cast(GCObject *, p + offset);
262 70922 o->marked = luaC_white(g);
263 70922 o->tt = tt;
264 70922 o->next = g->allgc;
265 70922 g->allgc = o;
266 70922 return o;
267 }
268
269
270 70922 GCObject *luaC_newobj (lua_State *L, int tt, size_t sz) {
271 70922 return luaC_newobjdt(L, tt, sz, 0);
272 }
273
274 /* }====================================================== */
275
276
277
278 /*
279 ** {======================================================
280 ** Mark functions
281 ** =======================================================
282 */
283
284
285 /*
286 ** Mark an object. Userdata with no user values, strings, and closed
287 ** upvalues are visited and turned black here. Open upvalues are
288 ** already indirectly linked through their respective threads in the
289 ** 'twups' list, so they don't go to the gray list; nevertheless, they
290 ** are kept gray to avoid barriers, as their values will be revisited
291 ** by the thread or by 'remarkupvals'. Other objects are added to the
292 ** gray list to be visited (and turned black) later. Both userdata and
293 ** upvalues can call this function recursively, but this recursion goes
294 ** for at most two levels: An upvalue cannot refer to another upvalue
295 ** (only closures can), and a userdata's metatable must be a table.
296 */
297 77517 static void reallymarkobject (global_State *g, GCObject *o) {
298
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 77517 switch (o->tt) {
299
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 46629 case LUA_VSHRSTR:
300 case LUA_VLNGSTR: {
301
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 46629 set2black(o); /* nothing to visit */
302 46629 break;
303 }
304 ✗ case LUA_VUPVAL: {
305 ✗ UpVal *uv = gco2upv(o);
306 ✗ if (upisopen(uv))
307 ✗ set2gray(uv); /* open upvalues are kept gray */
308 else
309 ✗ set2black(uv); /* closed upvalues are visited here */
310 ✗ markvalue(g, uv->v.p); /* mark its content */
311 ✗ break;
312 }
313
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 10395 case LUA_VUSERDATA: {
314 10395 Udata *u = gco2u(o);
315
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 10395 if (u->nuvalue == 0) { /* no user values? */
316
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 594 markobjectN(g, u->metatable); /* mark its metatable */
317 594 set2black(u); /* nothing else to mark */
318 594 break;
319 }
320 /* else... */
321 } /* FALLTHROUGH */
322 case LUA_VLCL: case LUA_VCCL: case LUA_VTABLE:
323 case LUA_VTHREAD: case LUA_VPROTO: {
324
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 30294 linkobjgclist(o, g->gray); /* to be visited later */
325 30294 break;
326 }
327 ✗ default: lua_assert(0); break;
328 }
329 77517 }
330
331
332 /*
333 ** mark metamethods for basic types
334 */
335 1782 static void markmt (global_State *g) {
336 int i;
337
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 17820 for (i=0; i < LUA_NUMTAGS; i++)
338
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 16038 markobjectN(g, g->mt[i]);
339 1782 }
340
341
342 /*
343 ** mark all objects in list of being-finalized
344 */
345 1782 static lu_mem markbeingfnz (global_State *g) {
346 GCObject *o;
347 1782 lu_mem count = 0;
348
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 1782 for (o = g->tobefnz; o != NULL; o = o->next) {
349 ✗ count++;
350 ✗ markobject(g, o);
351 }
352 1782 return count;
353 }
354
355
356 /*
357 ** For each non-marked thread, simulates a barrier between each open
358 ** upvalue and its value. (If the thread is collected, the value will be
359 ** assigned to the upvalue, but then it can be too late for the barrier
360 ** to act. The "barrier" does not need to check colors: A non-marked
361 ** thread must be young; upvalues cannot be older than their threads; so
362 ** any visited upvalue must be young too.) Also removes the thread from
363 ** the list, as it was already visited. Removes also threads with no
364 ** upvalues, as they have nothing to be checked. (If the thread gets an
365 ** upvalue later, it will be linked in the list again.)
366 */
367 891 static int remarkupvals (global_State *g) {
368 lua_State *thread;
369 891 lua_State **p = &g->twups;
370 891 int work = 0; /* estimate of how much work was done here */
371
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 891 while ((thread = *p) != NULL) {
372 ✗ work++;
373 ✗ if (!iswhite(thread) && thread->openupval != NULL)
374 ✗ p = &thread->twups; /* keep marked thread with upvalues in the list */
375 else { /* thread is not marked or without upvalues */
376 UpVal *uv;
377 lua_assert(!isold(thread) || thread->openupval == NULL);
378 ✗ *p = thread->twups; /* remove thread from the list */
379 ✗ thread->twups = thread; /* mark that it is out of list */
380 ✗ for (uv = thread->openupval; uv != NULL; uv = uv->u.open.next) {
381 lua_assert(getage(uv) <= getage(thread));
382 ✗ work++;
383 ✗ if (!iswhite(uv)) { /* upvalue already visited? */
384 lua_assert(upisopen(uv) && isgray(uv));
385 ✗ markvalue(g, uv->v.p); /* mark its value */
386 }
387 }
388 }
389 }
390 891 return work;
391 }
392
393
394 891 static void cleargraylists (global_State *g) {
395 891 g->gray = g->grayagain = NULL;
396 891 g->weak = g->allweak = g->ephemeron = NULL;
397 891 }
398
399
400 /*
401 ** mark root set and reset all gray lists, to start a new collection
402 */
403 891 static void restartcollection (global_State *g) {
404 891 cleargraylists(g);
405
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 891 markobject(g, g->mainthread);
406
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 891 markvalue(g, &g->l_registry);
407 891 markmt(g);
408 891 markbeingfnz(g); /* mark any finalizing object left from previous cycle */
409 891 }
410
411 /* }====================================================== */
412
413
414 /*
415 ** {======================================================
416 ** Traverse functions
417 ** =======================================================
418 */
419
420
421 /*
422 ** Check whether object 'o' should be kept in the 'grayagain' list for
423 ** post-processing by 'correctgraylist'. (It could put all old objects
424 ** in the list and leave all the work to 'correctgraylist', but it is
425 ** more efficient to avoid adding elements that will be removed.) Only
426 ** TOUCHED1 objects need to be in the list. TOUCHED2 doesn't need to go
427 ** back to a gray list, but then it must become OLD. (That is what
428 ** 'correctgraylist' does when it finds a TOUCHED2 object.)
429 */
430 21087 static void genlink (global_State *g, GCObject *o) {
431 lua_assert(isblack(o));
432
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 21087 if (getage(o) == G_TOUCHED1) { /* touched in this cycle? */
433 ✗ linkobjgclist(o, g->grayagain); /* link it back in 'grayagain' */
434 } /* everything else do not need to be linked back */
435
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 21087 else if (getage(o) == G_TOUCHED2)
436 ✗ changeage(o, G_TOUCHED2, G_OLD); /* advance age */
437 21087 }
438
439
440 /*
441 ** Traverse a table with weak values and link it to proper list. During
442 ** propagate phase, keep it in 'grayagain' list, to be revisited in the
443 ** atomic phase. In the atomic phase, if table has any white value,
444 ** put it in 'weak' list, to be cleared.
445 */
446 ✗ static void traverseweakvalue (global_State *g, Table *h) {
447 ✗ Node *n, *limit = gnodelast(h);
448 /* if there is array part, assume it may have white values (it is not
449 worth traversing it now just to check) */
450 ✗ int hasclears = (h->alimit > 0);
451 ✗ for (n = gnode(h, 0); n < limit; n++) { /* traverse hash part */
452 ✗ if (isempty(gval(n))) /* entry is empty? */
453 ✗ clearkey(n); /* clear its key */
454 else {
455 lua_assert(!keyisnil(n));
456 ✗ markkey(g, n);
457 ✗ if (!hasclears && iscleared(g, gcvalueN(gval(n)))) /* a white value? */
458 ✗ hasclears = 1; /* table will have to be cleared */
459 }
460 }
461 ✗ if (g->gcstate == GCSatomic && hasclears)
462 ✗ linkgclist(h, g->weak); /* has to be cleared later */
463 else
464 ✗ linkgclist(h, g->grayagain); /* must retraverse it in atomic phase */
465 ✗ }
466
467
468 /*
469 ** Traverse an ephemeron table and link it to proper list. Returns true
470 ** iff any object was marked during this traversal (which implies that
471 ** convergence has to continue). During propagation phase, keep table
472 ** in 'grayagain' list, to be visited again in the atomic phase. In
473 ** the atomic phase, if table has any white->white entry, it has to
474 ** be revisited during ephemeron convergence (as that key may turn
475 ** black). Otherwise, if it has any white key, table has to be cleared
476 ** (in the atomic phase). In generational mode, some tables
477 ** must be kept in some gray list for post-processing; this is done
478 ** by 'genlink'.
479 */
480 ✗ static int traverseephemeron (global_State *g, Table *h, int inv) {
481 ✗ int marked = 0; /* true if an object is marked in this traversal */
482 ✗ int hasclears = 0; /* true if table has white keys */
483 ✗ int hasww = 0; /* true if table has entry "white-key -> white-value" */
484 unsigned int i;
485 ✗ unsigned int asize = luaH_realasize(h);
486 ✗ unsigned int nsize = sizenode(h);
487 /* traverse array part */
488 ✗ for (i = 0; i < asize; i++) {
489 ✗ if (valiswhite(&h->array[i])) {
490 ✗ marked = 1;
491 ✗ reallymarkobject(g, gcvalue(&h->array[i]));
492 }
493 }
494 /* traverse hash part; if 'inv', traverse descending
495 (see 'convergeephemerons') */
496 ✗ for (i = 0; i < nsize; i++) {
497 ✗ Node *n = inv ? gnode(h, nsize - 1 - i) : gnode(h, i);
498 ✗ if (isempty(gval(n))) /* entry is empty? */
499 ✗ clearkey(n); /* clear its key */
500 ✗ else if (iscleared(g, gckeyN(n))) { /* key is not marked (yet)? */
501 ✗ hasclears = 1; /* table must be cleared */
502 ✗ if (valiswhite(gval(n))) /* value not marked yet? */
503 ✗ hasww = 1; /* white-white entry */
504 }
505 ✗ else if (valiswhite(gval(n))) { /* value not marked yet? */
506 ✗ marked = 1;
507 ✗ reallymarkobject(g, gcvalue(gval(n))); /* mark it now */
508 }
509 }
510 /* link table into proper list */
511 ✗ if (g->gcstate == GCSpropagate)
512 ✗ linkgclist(h, g->grayagain); /* must retraverse it in atomic phase */
513 ✗ else if (hasww) /* table has white->white entries? */
514 ✗ linkgclist(h, g->ephemeron); /* have to propagate again */
515 ✗ else if (hasclears) /* table has white keys? */
516 ✗ linkgclist(h, g->allweak); /* may have to clean white keys */
517 else
518 ✗ genlink(g, obj2gco(h)); /* check whether collector still needs to see it */
519 ✗ return marked;
520 }
521
522
523 11286 static void traversestrongtable (global_State *g, Table *h) {
524 11286 Node *n, *limit = gnodelast(h);
525 unsigned int i;
526 11286 unsigned int asize = luaH_realasize(h);
527
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 13068 for (i = 0; i < asize; i++) /* traverse array part */
528
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 1782 markvalue(g, &h->array[i]);
529
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 88506 for (n = gnode(h, 0); n < limit; n++) { /* traverse hash part */
530
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 77220 if (isempty(gval(n))) /* entry is empty? */
531 10989 clearkey(n); /* clear its key */
532 else {
533 lua_assert(!keyisnil(n));
534
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 66231 markkey(g, n);
535
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 66231 markvalue(g, gval(n));
536 }
537 }
538 11286 genlink(g, obj2gco(h));
539 11286 }
540
541
542 11286 static lu_mem traversetable (global_State *g, Table *h) {
543 const char *weakkey, *weakvalue;
544
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 11286 const TValue *mode = gfasttm(g, h->metatable, TM_MODE);
545
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 11286 markobjectN(g, h->metatable);
546
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 11286 if (mode && ttisstring(mode) && /* is there a weak mode? */
547 ✗ (cast_void(weakkey = strchr(svalue(mode), 'k')),
548 ✗ cast_void(weakvalue = strchr(svalue(mode), 'v')),
549 ✗ (weakkey || weakvalue))) { /* is really weak? */
550 ✗ if (!weakkey) /* strong keys? */
551 ✗ traverseweakvalue(g, h);
552 ✗ else if (!weakvalue) /* strong values? */
553 ✗ traverseephemeron(g, h, 0);
554 else /* all weak */
555 ✗ linkgclist(h, g->allweak); /* nothing to traverse now */
556 }
557 else /* not weak */
558 11286 traversestrongtable(g, h);
559
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 11286 return 1 + h->alimit + 2 * allocsizenode(h);
560 }
561
562
563 9801 static int traverseudata (global_State *g, Udata *u) {
564 int i;
565
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 9801 markobjectN(g, u->metatable); /* mark its metatable */
566
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 19602 for (i = 0; i < u->nuvalue; i++)
567
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 9801 markvalue(g, &u->uv[i].uv);
568 9801 genlink(g, obj2gco(u));
569 9801 return 1 + u->nuvalue;
570 }
571
572
573 /*
574 ** Traverse a prototype. (While a prototype is being build, its
575 ** arrays can be larger than needed; the extra slots are filled with
576 ** NULL, so the use of 'markobjectN')
577 */
578 ✗ static int traverseproto (global_State *g, Proto *f) {
579 int i;
580 ✗ markobjectN(g, f->source);
581 ✗ for (i = 0; i < f->sizek; i++) /* mark literals */
582 ✗ markvalue(g, &f->k[i]);
583 ✗ for (i = 0; i < f->sizeupvalues; i++) /* mark upvalue names */
584 ✗ markobjectN(g, f->upvalues[i].name);
585 ✗ for (i = 0; i < f->sizep; i++) /* mark nested protos */
586 ✗ markobjectN(g, f->p[i]);
587 ✗ for (i = 0; i < f->sizelocvars; i++) /* mark local-variable names */
588 ✗ markobjectN(g, f->locvars[i].varname);
589 ✗ return 1 + f->sizek + f->sizeupvalues + f->sizep + f->sizelocvars;
590 }
591
592
593 8316 static int traverseCclosure (global_State *g, CClosure *cl) {
594 int i;
595
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 16632 for (i = 0; i < cl->nupvalues; i++) /* mark its upvalues */
596
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 8316 markvalue(g, &cl->upvalue[i]);
597 8316 return 1 + cl->nupvalues;
598 }
599
600 /*
601 ** Traverse a Lua closure, marking its prototype and its upvalues.
602 ** (Both can be NULL while closure is being created.)
603 */
604 ✗ static int traverseLclosure (global_State *g, LClosure *cl) {
605 int i;
606 ✗ markobjectN(g, cl->p); /* mark its prototype */
607 ✗ for (i = 0; i < cl->nupvalues; i++) { /* visit its upvalues */
608 ✗ UpVal *uv = cl->upvals[i];
609 ✗ markobjectN(g, uv); /* mark upvalue */
610 }
611 ✗ return 1 + cl->nupvalues;
612 }
613
614
615 /*
616 ** Traverse a thread, marking the elements in the stack up to its top
617 ** and cleaning the rest of the stack in the final traversal. That
618 ** ensures that the entire stack have valid (non-dead) objects.
619 ** Threads have no barriers. In gen. mode, old threads must be visited
620 ** at every cycle, because they might point to young objects. In inc.
621 ** mode, the thread can still be modified before the end of the cycle,
622 ** and therefore it must be visited again in the atomic phase. To ensure
623 ** these visits, threads must return to a gray list if they are not new
624 ** (which can only happen in generational mode) or if the traverse is in
625 ** the propagate phase (which can only happen in incremental mode).
626 */
627 1782 static int traversethread (global_State *g, lua_State *th) {
628 UpVal *uv;
629 1782 StkId o = th->stack.p;
630
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 1782 if (isold(th) || g->gcstate == GCSpropagate)
631 891 linkgclist(th, g->grayagain); /* insert into 'grayagain' list */
632
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 1782 if (o == NULL)
633 ✗ return 1; /* stack not completely built yet */
634 lua_assert(g->gcstate == GCSatomic ||
635 th->openupval == NULL || isintwups(th));
636
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 5346 for (; o < th->top.p; o++) /* mark live elements in the stack */
637
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 3564 markvalue(g, s2v(o));
638
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 1782 for (uv = th->openupval; uv != NULL; uv = uv->u.open.next)
639 ✗ markobject(g, uv); /* open upvalues cannot be collected */
640
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 1782 if (g->gcstate == GCSatomic) { /* final traversal? */
641
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 39204 for (; o < th->stack_last.p + EXTRA_STACK; o++)
642 38313 setnilvalue(s2v(o)); /* clear dead stack slice */
643 /* 'remarkupvals' may have removed thread from 'twups' list */
644
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 891 if (!isintwups(th) && th->openupval != NULL) {
645 ✗ th->twups = g->twups; /* link it back to the list */
646 ✗ g->twups = th;
647 }
648 }
649
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 891 else if (!g->gcemergency)
650 891 luaD_shrinkstack(th); /* do not change stack in emergency cycle */
651 1782 return 1 + stacksize(th);
652 }
653
654
655 /*
656 ** traverse one gray object, turning it to black.
657 */
658 31185 static lu_mem propagatemark (global_State *g) {
659 31185 GCObject *o = g->gray;
660 31185 nw2black(o);
661 31185 g->gray = *getgclist(o); /* remove from 'gray' list */
662
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 31185 switch (o->tt) {
663
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 11286 case LUA_VTABLE: return traversetable(g, gco2t(o));
664
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 9801 case LUA_VUSERDATA: return traverseudata(g, gco2u(o));
665 ✗ case LUA_VLCL: return traverseLclosure(g, gco2lcl(o));
666
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 8316 case LUA_VCCL: return traverseCclosure(g, gco2ccl(o));
667 ✗ case LUA_VPROTO: return traverseproto(g, gco2p(o));
668
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 1782 case LUA_VTHREAD: return traversethread(g, gco2th(o));
669 ✗ default: lua_assert(0); return 0;
670 }
671 }
672
673
674 3564 static lu_mem propagateall (global_State *g) {
675 3564 lu_mem tot = 0;
676
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 4455 while (g->gray)
677 891 tot += propagatemark(g);
678 3564 return tot;
679 }
680
681
682 /*
683 ** Traverse all ephemeron tables propagating marks from keys to values.
684 ** Repeat until it converges, that is, nothing new is marked. 'dir'
685 ** inverts the direction of the traversals, trying to speed up
686 ** convergence on chains in the same table.
687 **
688 */
689 1782 static void convergeephemerons (global_State *g) {
690 int changed;
691 1782 int dir = 0;
692 do {
693 GCObject *w;
694 1782 GCObject *next = g->ephemeron; /* get ephemeron list */
695 1782 g->ephemeron = NULL; /* tables may return to this list when traversed */
696 1782 changed = 0;
697
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 1782 while ((w = next) != NULL) { /* for each ephemeron table */
698 ✗ Table *h = gco2t(w);
699 ✗ next = h->gclist; /* list is rebuilt during loop */
700 ✗ nw2black(h); /* out of the list (for now) */
701 ✗ if (traverseephemeron(g, h, dir)) { /* marked some value? */
702 ✗ propagateall(g); /* propagate changes */
703 ✗ changed = 1; /* will have to revisit all ephemeron tables */
704 }
705 }
706 1782 dir = !dir; /* invert direction next time */
707
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 1782 } while (changed); /* repeat until no more changes */
708 1782 }
709
710 /* }====================================================== */
711
712
713 /*
714 ** {======================================================
715 ** Sweep Functions
716 ** =======================================================
717 */
718
719
720 /*
721 ** clear entries with unmarked keys from all weaktables in list 'l'
722 */
723 1782 static void clearbykeys (global_State *g, GCObject *l) {
724
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 1782 for (; l; l = gco2t(l)->gclist) {
725 ✗ Table *h = gco2t(l);
726 ✗ Node *limit = gnodelast(h);
727 Node *n;
728 ✗ for (n = gnode(h, 0); n < limit; n++) {
729 ✗ if (iscleared(g, gckeyN(n))) /* unmarked key? */
730 ✗ setempty(gval(n)); /* remove entry */
731 ✗ if (isempty(gval(n))) /* is entry empty? */
732 ✗ clearkey(n); /* clear its key */
733 }
734 }
735 1782 }
736
737
738 /*
739 ** clear entries with unmarked values from all weaktables in list 'l' up
740 ** to element 'f'
741 */
742 3564 static void clearbyvalues (global_State *g, GCObject *l, GCObject *f) {
743
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 3564 for (; l != f; l = gco2t(l)->gclist) {
744 ✗ Table *h = gco2t(l);
745 ✗ Node *n, *limit = gnodelast(h);
746 unsigned int i;
747 ✗ unsigned int asize = luaH_realasize(h);
748 ✗ for (i = 0; i < asize; i++) {
749 ✗ TValue *o = &h->array[i];
750 ✗ if (iscleared(g, gcvalueN(o))) /* value was collected? */
751 ✗ setempty(o); /* remove entry */
752 }
753 ✗ for (n = gnode(h, 0); n < limit; n++) {
754 ✗ if (iscleared(g, gcvalueN(gval(n)))) /* unmarked value? */
755 ✗ setempty(gval(n)); /* remove entry */
756 ✗ if (isempty(gval(n))) /* is entry empty? */
757 ✗ clearkey(n); /* clear its key */
758 }
759 }
760 3564 }
761
762
763 296 static void freeupval (lua_State *L, UpVal *uv) {
764
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 296 if (upisopen(uv))
765 ✗ luaF_unlinkupval(uv);
766 296 luaM_free(L, uv);
767 296 }
768
769
770 70922 static void freeobj (lua_State *L, GCObject *o) {
771
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 70922 switch (o->tt) {
772
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 512 case LUA_VPROTO:
773 512 luaF_freeproto(L, gco2p(o));
774 512 break;
775
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 296 case LUA_VUPVAL:
776 296 freeupval(L, gco2upv(o));
777 296 break;
778
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 512 case LUA_VLCL: {
779 512 LClosure *cl = gco2lcl(o);
780 512 luaM_freemem(L, cl, sizeLclosure(cl->nupvalues));
781 512 break;
782 }
783
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 5940 case LUA_VCCL: {
784 5940 CClosure *cl = gco2ccl(o);
785 5940 luaM_freemem(L, cl, sizeCclosure(cl->nupvalues));
786 5940 break;
787 }
788
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 6937 case LUA_VTABLE:
789 6937 luaH_free(L, gco2t(o));
790 6937 break;
791 ✗ case LUA_VTHREAD:
792 ✗ luaE_freethread(L, gco2th(o));
793 ✗ break;
794
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 7431 case LUA_VUSERDATA: {
795 7431 Udata *u = gco2u(o);
796
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 7431 luaM_freemem(L, o, sizeudata(u->nuvalue, u->len));
797 7431 break;
798 }
799
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 49179 case LUA_VSHRSTR: {
800 49179 TString *ts = gco2ts(o);
801 49179 luaS_remove(L, ts); /* remove it from hash table */
802 49179 luaM_freemem(L, ts, sizelstring(ts->shrlen));
803 49179 break;
804 }
805
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 115 case LUA_VLNGSTR: {
806 115 TString *ts = gco2ts(o);
807 115 luaM_freemem(L, ts, sizelstring(ts->u.lnglen));
808 115 break;
809 }
810
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 70922 default: lua_assert(0);
811 }
812 70922 }
813
814
815 /*
816 ** sweep at most 'countin' elements from a list of GCObjects erasing dead
817 ** objects, where a dead object is one marked with the old (non current)
818 ** white; change all non-dead objects back to white, preparing for next
819 ** collection cycle. Return where to continue the traversal or NULL if
820 ** list is finished. ('*countout' gets the number of elements traversed.)
821 */
822 3861 static GCObject **sweeplist (lua_State *L, GCObject **p, int countin,
823 int *countout) {
824 3861 global_State *g = G(L);
825 3861 int ow = otherwhite(g);
826 int i;
827 3861 int white = luaC_white(g); /* current white */
828
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 81675 for (i = 0; *p != NULL && i < countin; i++) {
829 77814 GCObject *curr = *p;
830 77814 int marked = curr->marked;
831
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 77814 if (isdeadm(ow, marked)) { /* is 'curr' dead? */
832 297 *p = curr->next; /* remove 'curr' from list */
833 297 freeobj(L, curr); /* erase 'curr' */
834 }
835 else { /* change mark to 'white' */
836 77517 curr->marked = cast_byte((marked & ~maskgcbits) | white);
837 77517 p = &curr->next; /* go to next element */
838 }
839 }
840
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 3861 if (countout)
841 2970 *countout = i; /* number of elements traversed */
842
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 3861 return (*p == NULL) ? NULL : p;
843 }
844
845
846 /*
847 ** sweep a list until a live object (or end of list)
848 */
849 891 static GCObject **sweeptolive (lua_State *L, GCObject **p) {
850 891 GCObject **old = p;
851 do {
852 891 p = sweeplist(L, p, 1, NULL);
853
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 891 } while (p == old);
854 891 return p;
855 }
856
857 /* }====================================================== */
858
859
860 /*
861 ** {======================================================
862 ** Finalization
863 ** =======================================================
864 */
865
866 /*
867 ** If possible, shrink string table.
868 */
869 891 static void checkSizes (lua_State *L, global_State *g) {
870
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 891 if (!g->gcemergency) {
871
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 891 if (g->strt.nuse < g->strt.size / 4) { /* string table too big? */
872 ✗ l_mem olddebt = g->GCdebt;
873 ✗ luaS_resize(L, g->strt.size / 2);
874 ✗ g->GCestimate += g->GCdebt - olddebt; /* correct estimate */
875 }
876 }
877 891 }
878
879
880 /*
881 ** Get the next udata to be finalized from the 'tobefnz' list, and
882 ** link it back into the 'allgc' list.
883 */
884 1788 static GCObject *udata2finalize (global_State *g) {
885 1788 GCObject *o = g->tobefnz; /* get first element */
886 lua_assert(tofinalize(o));
887 1788 g->tobefnz = o->next; /* remove it from 'tobefnz' list */
888 1788 o->next = g->allgc; /* return it to 'allgc' list */
889 1788 g->allgc = o;
890 1788 resetbit(o->marked, FINALIZEDBIT); /* object is "normal" again */
891
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 1788 if (issweepphase(g))
892 ✗ makewhite(g, o); /* "sweep" object */
893
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 1788 else if (getage(o) == G_OLD1)
894 ✗ g->firstold1 = o; /* it is the first OLD1 object in the list */
895 1788 return o;
896 }
897
898
899 1788 static void dothecall (lua_State *L, void *ud) {
900 UNUSED(ud);
901 1788 luaD_callnoyield(L, L->top.p - 2, 0);
902 1788 }
903
904
905 1788 static void GCTM (lua_State *L) {
906 1788 global_State *g = G(L);
907 const TValue *tm;
908 TValue v;
909 lua_assert(!g->gcemergency);
910 1788 setgcovalue(L, &v, udata2finalize(g));
911 1788 tm = luaT_gettmbyobj(L, &v, TM_GC);
912
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 1788 if (!notm(tm)) { /* is there a finalizer? */
913 int status;
914 1788 lu_byte oldah = L->allowhook;
915 1788 int oldgcstp = g->gcstp;
916 1788 g->gcstp |= GCSTPGC; /* avoid GC steps */
917 1788 L->allowhook = 0; /* stop debug hooks during GC metamethod */
918 1788 setobj2s(L, L->top.p++, tm); /* push finalizer... */
919 1788 setobj2s(L, L->top.p++, &v); /* ... and its argument */
920 1788 L->ci->callstatus |= CIST_FIN; /* will run a finalizer */
921 1788 status = luaD_pcall(L, dothecall, NULL, savestack(L, L->top.p - 2), 0);
922 1788 L->ci->callstatus &= ~CIST_FIN; /* not running a finalizer anymore */
923 1788 L->allowhook = oldah; /* restore hooks */
924 1788 g->gcstp = oldgcstp; /* restore state */
925
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 1788 if (l_unlikely(status != LUA_OK)) { /* error while running __gc? */
926 ✗ luaE_warnerror(L, "__gc");
927 ✗ L->top.p--; /* pops error object */
928 }
929 }
930 1788 }
931
932
933 /*
934 ** Call a few finalizers
935 */
936 ✗ static int runafewfinalizers (lua_State *L, int n) {
937 ✗ global_State *g = G(L);
938 int i;
939 ✗ for (i = 0; i < n && g->tobefnz; i++)
940 ✗ GCTM(L); /* call one finalizer */
941 ✗ return i;
942 }
943
944
945 /*
946 ** call all pending finalizers
947 */
948 297 static void callallpendingfinalizers (lua_State *L) {
949 297 global_State *g = G(L);
950
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 2085 while (g->tobefnz)
951 1788 GCTM(L);
952 297 }
953
954
955 /*
956 ** find last 'next' field in list 'p' list (to add elements in its end)
957 */
958 1188 static GCObject **findlast (GCObject **p) {
959
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 1188 while (*p != NULL)
960 ✗ p = &(*p)->next;
961 1188 return p;
962 }
963
964
965 /*
966 ** Move all unreachable objects (or 'all' objects) that need
967 ** finalization from list 'finobj' to list 'tobefnz' (to be finalized).
968 ** (Note that objects after 'finobjold1' cannot be white, so they
969 ** don't need to be traversed. In incremental mode, 'finobjold1' is NULL,
970 ** so the whole list is traversed.)
971 */
972 1188 static void separatetobefnz (global_State *g, int all) {
973 GCObject *curr;
974 1188 GCObject **p = &g->finobj;
975 1188 GCObject **lastnext = findlast(&g->tobefnz);
976
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 5649 while ((curr = *p) != g->finobjold1) { /* traverse all finalizable objects */
977 lua_assert(tofinalize(curr));
978
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 4461 if (!(iswhite(curr) || all)) /* not being collected? */
979 2673 p = &curr->next; /* don't bother with it */
980 else {
981
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 1788 if (curr == g->finobjsur) /* removing 'finobjsur'? */
982 ✗ g->finobjsur = curr->next; /* correct it */
983 1788 *p = curr->next; /* remove 'curr' from 'finobj' list */
984 1788 curr->next = *lastnext; /* link at the end of 'tobefnz' list */
985 1788 *lastnext = curr;
986 1788 lastnext = &curr->next;
987 }
988 }
989 1188 }
990
991
992 /*
993 ** If pointer 'p' points to 'o', move it to the next element.
994 */
995 7152 static void checkpointer (GCObject **p, GCObject *o) {
996
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 7152 if (o == *p)
997 ✗ *p = o->next;
998 7152 }
999
1000
1001 /*
1002 ** Correct pointers to objects inside 'allgc' list when
1003 ** object 'o' is being removed from the list.
1004 */
1005 1788 static void correctpointers (global_State *g, GCObject *o) {
1006 1788 checkpointer(&g->survival, o);
1007 1788 checkpointer(&g->old1, o);
1008 1788 checkpointer(&g->reallyold, o);
1009 1788 checkpointer(&g->firstold1, o);
1010 1788 }
1011
1012
1013 /*
1014 ** if object 'o' has a finalizer, remove it from 'allgc' list (must
1015 ** search the list to find it) and link it in 'finobj' list.
1016 */
1017 1788 void luaC_checkfinalizer (lua_State *L, GCObject *o, Table *mt) {
1018 1788 global_State *g = G(L);
1019
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 1788 if (tofinalize(o) || /* obj. is already marked... */
1020
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 1788 gfasttm(g, mt, TM_GC) == NULL || /* or has no finalizer... */
1021
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 1788 (g->gcstp & GCSTPCLS)) /* or closing state? */
1022 ✗ return; /* nothing to be done */
1023 else { /* move 'o' to 'finobj' list */
1024 GCObject **p;
1025
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 1788 if (issweepphase(g)) {
1026 ✗ makewhite(g, o); /* "sweep" object 'o' */
1027 ✗ if (g->sweepgc == &o->next) /* should not remove 'sweepgc' object */
1028 ✗ g->sweepgc = sweeptolive(L, g->sweepgc); /* change 'sweepgc' */
1029 }
1030 else
1031 1788 correctpointers(g, o);
1032 /* search for pointer pointing to 'o' */
1033
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 5649 for (p = &g->allgc; *p != o; p = &(*p)->next) { /* empty */ }
1034 1788 *p = o->next; /* remove 'o' from 'allgc' list */
1035 1788 o->next = g->finobj; /* link it in 'finobj' list */
1036 1788 g->finobj = o;
1037 1788 l_setbit(o->marked, FINALIZEDBIT); /* mark it as such */
1038 }
1039 }
1040
1041 /* }====================================================== */
1042
1043
1044 /*
1045 ** {======================================================
1046 ** Generational Collector
1047 ** =======================================================
1048 */
1049
1050
1051 /*
1052 ** Set the "time" to wait before starting a new GC cycle; cycle will
1053 ** start when memory use hits the threshold of ('estimate' * pause /
1054 ** PAUSEADJ). (Division by 'estimate' should be OK: it cannot be zero,
1055 ** because Lua cannot even start with less than PAUSEADJ bytes).
1056 */
1057 891 static void setpause (global_State *g) {
1058 l_mem threshold, debt;
1059 891 int pause = getgcparam(g->gcpause);
1060 891 l_mem estimate = g->GCestimate / PAUSEADJ; /* adjust 'estimate' */
1061 lua_assert(estimate > 0);
1062 1782 threshold = (pause < MAX_LMEM / estimate) /* overflow? */
1063 891 ? estimate * pause /* no overflow */
1064
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 891 : MAX_LMEM; /* overflow; truncate to maximum */
1065 891 debt = gettotalbytes(g) - threshold;
1066
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 891 if (debt > 0) debt = 0;
1067 891 luaE_setdebt(g, debt);
1068 891 }
1069
1070
1071 /*
1072 ** Sweep a list of objects to enter generational mode. Deletes dead
1073 ** objects and turns the non dead to old. All non-dead threads---which
1074 ** are now old---must be in a gray list. Everything else is not in a
1075 ** gray list. Open upvalues are also kept gray.
1076 */
1077 ✗ static void sweep2old (lua_State *L, GCObject **p) {
1078 GCObject *curr;
1079 ✗ global_State *g = G(L);
1080 ✗ while ((curr = *p) != NULL) {
1081 ✗ if (iswhite(curr)) { /* is 'curr' dead? */
1082 lua_assert(isdead(g, curr));
1083 ✗ *p = curr->next; /* remove 'curr' from list */
1084 ✗ freeobj(L, curr); /* erase 'curr' */
1085 }
1086 else { /* all surviving objects become old */
1087 ✗ setage(curr, G_OLD);
1088 ✗ if (curr->tt == LUA_VTHREAD) { /* threads must be watched */
1089 ✗ lua_State *th = gco2th(curr);
1090 ✗ linkgclist(th, g->grayagain); /* insert into 'grayagain' list */
1091 }
1092 ✗ else if (curr->tt == LUA_VUPVAL && upisopen(gco2upv(curr)))
1093 ✗ set2gray(curr); /* open upvalues are always gray */
1094 else /* everything else is black */
1095 ✗ nw2black(curr);
1096 ✗ p = &curr->next; /* go to next element */
1097 }
1098 }
1099 ✗ }
1100
1101
1102 /*
1103 ** Sweep for generational mode. Delete dead objects. (Because the
1104 ** collection is not incremental, there are no "new white" objects
1105 ** during the sweep. So, any white object must be dead.) For
1106 ** non-dead objects, advance their ages and clear the color of
1107 ** new objects. (Old objects keep their colors.)
1108 ** The ages of G_TOUCHED1 and G_TOUCHED2 objects cannot be advanced
1109 ** here, because these old-generation objects are usually not swept
1110 ** here. They will all be advanced in 'correctgraylist'. That function
1111 ** will also remove objects turned white here from any gray list.
1112 */
1113 ✗ static GCObject **sweepgen (lua_State *L, global_State *g, GCObject **p,
1114 GCObject *limit, GCObject **pfirstold1) {
1115 static const lu_byte nextage[] = {
1116 G_SURVIVAL, /* from G_NEW */
1117 G_OLD1, /* from G_SURVIVAL */
1118 G_OLD1, /* from G_OLD0 */
1119 G_OLD, /* from G_OLD1 */
1120 G_OLD, /* from G_OLD (do not change) */
1121 G_TOUCHED1, /* from G_TOUCHED1 (do not change) */
1122 G_TOUCHED2 /* from G_TOUCHED2 (do not change) */
1123 };
1124 ✗ int white = luaC_white(g);
1125 GCObject *curr;
1126 ✗ while ((curr = *p) != limit) {
1127 ✗ if (iswhite(curr)) { /* is 'curr' dead? */
1128 lua_assert(!isold(curr) && isdead(g, curr));
1129 ✗ *p = curr->next; /* remove 'curr' from list */
1130 ✗ freeobj(L, curr); /* erase 'curr' */
1131 }
1132 else { /* correct mark and age */
1133 ✗ if (getage(curr) == G_NEW) { /* new objects go back to white */
1134 ✗ int marked = curr->marked & ~maskgcbits; /* erase GC bits */
1135 ✗ curr->marked = cast_byte(marked | G_SURVIVAL | white);
1136 }
1137 else { /* all other objects will be old, and so keep their color */
1138 ✗ setage(curr, nextage[getage(curr)]);
1139 ✗ if (getage(curr) == G_OLD1 && *pfirstold1 == NULL)
1140 ✗ *pfirstold1 = curr; /* first OLD1 object in the list */
1141 }
1142 ✗ p = &curr->next; /* go to next element */
1143 }
1144 }
1145 ✗ return p;
1146 }
1147
1148
1149 /*
1150 ** Traverse a list making all its elements white and clearing their
1151 ** age. In incremental mode, all objects are 'new' all the time,
1152 ** except for fixed strings (which are always old).
1153 */
1154 ✗ static void whitelist (global_State *g, GCObject *p) {
1155 ✗ int white = luaC_white(g);
1156 ✗ for (; p != NULL; p = p->next)
1157 ✗ p->marked = cast_byte((p->marked & ~maskgcbits) | white);
1158 ✗ }
1159
1160
1161 /*
1162 ** Correct a list of gray objects. Return pointer to where rest of the
1163 ** list should be linked.
1164 ** Because this correction is done after sweeping, young objects might
1165 ** be turned white and still be in the list. They are only removed.
1166 ** 'TOUCHED1' objects are advanced to 'TOUCHED2' and remain on the list;
1167 ** Non-white threads also remain on the list; 'TOUCHED2' objects become
1168 ** regular old; they and anything else are removed from the list.
1169 */
1170 ✗ static GCObject **correctgraylist (GCObject **p) {
1171 GCObject *curr;
1172 ✗ while ((curr = *p) != NULL) {
1173 ✗ GCObject **next = getgclist(curr);
1174 ✗ if (iswhite(curr))
1175 ✗ goto remove; /* remove all white objects */
1176 ✗ else if (getage(curr) == G_TOUCHED1) { /* touched in this cycle? */
1177 lua_assert(isgray(curr));
1178 ✗ nw2black(curr); /* make it black, for next barrier */
1179 ✗ changeage(curr, G_TOUCHED1, G_TOUCHED2);
1180 ✗ goto remain; /* keep it in the list and go to next element */
1181 }
1182 ✗ else if (curr->tt == LUA_VTHREAD) {
1183 lua_assert(isgray(curr));
1184 ✗ goto remain; /* keep non-white threads on the list */
1185 }
1186 else { /* everything else is removed */
1187 lua_assert(isold(curr)); /* young objects should be white here */
1188 ✗ if (getage(curr) == G_TOUCHED2) /* advance from TOUCHED2... */
1189 ✗ changeage(curr, G_TOUCHED2, G_OLD); /* ... to OLD */
1190 ✗ nw2black(curr); /* make object black (to be removed) */
1191 ✗ goto remove;
1192 }
1193 ✗ remove: *p = *next; continue;
1194 ✗ remain: p = next; continue;
1195 }
1196 ✗ return p;
1197 }
1198
1199
1200 /*
1201 ** Correct all gray lists, coalescing them into 'grayagain'.
1202 */
1203 ✗ static void correctgraylists (global_State *g) {
1204 ✗ GCObject **list = correctgraylist(&g->grayagain);
1205 ✗ *list = g->weak; g->weak = NULL;
1206 ✗ list = correctgraylist(list);
1207 ✗ *list = g->allweak; g->allweak = NULL;
1208 ✗ list = correctgraylist(list);
1209 ✗ *list = g->ephemeron; g->ephemeron = NULL;
1210 ✗ correctgraylist(list);
1211 ✗ }
1212
1213
1214 /*
1215 ** Mark black 'OLD1' objects when starting a new young collection.
1216 ** Gray objects are already in some gray list, and so will be visited
1217 ** in the atomic step.
1218 */
1219 ✗ static void markold (global_State *g, GCObject *from, GCObject *to) {
1220 GCObject *p;
1221 ✗ for (p = from; p != to; p = p->next) {
1222 ✗ if (getage(p) == G_OLD1) {
1223 lua_assert(!iswhite(p));
1224 ✗ changeage(p, G_OLD1, G_OLD); /* now they are old */
1225 ✗ if (isblack(p))
1226 ✗ reallymarkobject(g, p);
1227 }
1228 }
1229 ✗ }
1230
1231
1232 /*
1233 ** Finish a young-generation collection.
1234 */
1235 ✗ static void finishgencycle (lua_State *L, global_State *g) {
1236 ✗ correctgraylists(g);
1237 ✗ checkSizes(L, g);
1238 ✗ g->gcstate = GCSpropagate; /* skip restart */
1239 ✗ if (!g->gcemergency)
1240 ✗ callallpendingfinalizers(L);
1241 ✗ }
1242
1243
1244 /*
1245 ** Does a young collection. First, mark 'OLD1' objects. Then does the
1246 ** atomic step. Then, sweep all lists and advance pointers. Finally,
1247 ** finish the collection.
1248 */
1249 ✗ static void youngcollection (lua_State *L, global_State *g) {
1250 GCObject **psurvival; /* to point to first non-dead survival object */
1251 GCObject *dummy; /* dummy out parameter to 'sweepgen' */
1252 lua_assert(g->gcstate == GCSpropagate);
1253 ✗ if (g->firstold1) { /* are there regular OLD1 objects? */
1254 ✗ markold(g, g->firstold1, g->reallyold); /* mark them */
1255 ✗ g->firstold1 = NULL; /* no more OLD1 objects (for now) */
1256 }
1257 ✗ markold(g, g->finobj, g->finobjrold);
1258 ✗ markold(g, g->tobefnz, NULL);
1259 ✗ atomic(L);
1260
1261 /* sweep nursery and get a pointer to its last live element */
1262 ✗ g->gcstate = GCSswpallgc;
1263 ✗ psurvival = sweepgen(L, g, &g->allgc, g->survival, &g->firstold1);
1264 /* sweep 'survival' */
1265 ✗ sweepgen(L, g, psurvival, g->old1, &g->firstold1);
1266 ✗ g->reallyold = g->old1;
1267 ✗ g->old1 = *psurvival; /* 'survival' survivals are old now */
1268 ✗ g->survival = g->allgc; /* all news are survivals */
1269
1270 /* repeat for 'finobj' lists */
1271 ✗ dummy = NULL; /* no 'firstold1' optimization for 'finobj' lists */
1272 ✗ psurvival = sweepgen(L, g, &g->finobj, g->finobjsur, &dummy);
1273 /* sweep 'survival' */
1274 ✗ sweepgen(L, g, psurvival, g->finobjold1, &dummy);
1275 ✗ g->finobjrold = g->finobjold1;
1276 ✗ g->finobjold1 = *psurvival; /* 'survival' survivals are old now */
1277 ✗ g->finobjsur = g->finobj; /* all news are survivals */
1278
1279 ✗ sweepgen(L, g, &g->tobefnz, NULL, &dummy);
1280 ✗ finishgencycle(L, g);
1281 ✗ }
1282
1283
1284 /*
1285 ** Clears all gray lists, sweeps objects, and prepare sublists to enter
1286 ** generational mode. The sweeps remove dead objects and turn all
1287 ** surviving objects to old. Threads go back to 'grayagain'; everything
1288 ** else is turned black (not in any gray list).
1289 */
1290 ✗ static void atomic2gen (lua_State *L, global_State *g) {
1291 ✗ cleargraylists(g);
1292 /* sweep all elements making them old */
1293 ✗ g->gcstate = GCSswpallgc;
1294 ✗ sweep2old(L, &g->allgc);
1295 /* everything alive now is old */
1296 ✗ g->reallyold = g->old1 = g->survival = g->allgc;
1297 ✗ g->firstold1 = NULL; /* there are no OLD1 objects anywhere */
1298
1299 /* repeat for 'finobj' lists */
1300 ✗ sweep2old(L, &g->finobj);
1301 ✗ g->finobjrold = g->finobjold1 = g->finobjsur = g->finobj;
1302
1303 ✗ sweep2old(L, &g->tobefnz);
1304
1305 ✗ g->gckind = KGC_GEN;
1306 ✗ g->lastatomic = 0;
1307 ✗ g->GCestimate = gettotalbytes(g); /* base for memory control */
1308 ✗ finishgencycle(L, g);
1309 ✗ }
1310
1311
1312 /*
1313 ** Set debt for the next minor collection, which will happen when
1314 ** memory grows 'genminormul'%.
1315 */
1316 ✗ static void setminordebt (global_State *g) {
1317 ✗ luaE_setdebt(g, -(cast(l_mem, (gettotalbytes(g) / 100)) * g->genminormul));
1318 ✗ }
1319
1320
1321 /*
1322 ** Enter generational mode. Must go until the end of an atomic cycle
1323 ** to ensure that all objects are correctly marked and weak tables
1324 ** are cleared. Then, turn all objects into old and finishes the
1325 ** collection.
1326 */
1327 ✗ static lu_mem entergen (lua_State *L, global_State *g) {
1328 lu_mem numobjs;
1329 ✗ luaC_runtilstate(L, bitmask(GCSpause)); /* prepare to start a new cycle */
1330 ✗ luaC_runtilstate(L, bitmask(GCSpropagate)); /* start new cycle */
1331 ✗ numobjs = atomic(L); /* propagates all and then do the atomic stuff */
1332 ✗ atomic2gen(L, g);
1333 ✗ setminordebt(g); /* set debt assuming next cycle will be minor */
1334 ✗ return numobjs;
1335 }
1336
1337
1338 /*
1339 ** Enter incremental mode. Turn all objects white, make all
1340 ** intermediate lists point to NULL (to avoid invalid pointers),
1341 ** and go to the pause state.
1342 */
1343 ✗ static void enterinc (global_State *g) {
1344 ✗ whitelist(g, g->allgc);
1345 ✗ g->reallyold = g->old1 = g->survival = NULL;
1346 ✗ whitelist(g, g->finobj);
1347 ✗ whitelist(g, g->tobefnz);
1348 ✗ g->finobjrold = g->finobjold1 = g->finobjsur = NULL;
1349 ✗ g->gcstate = GCSpause;
1350 ✗ g->gckind = KGC_INC;
1351 ✗ g->lastatomic = 0;
1352 ✗ }
1353
1354
1355 /*
1356 ** Change collector mode to 'newmode'.
1357 */
1358 594 void luaC_changemode (lua_State *L, int newmode) {
1359 594 global_State *g = G(L);
1360
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 594 if (newmode != g->gckind) {
1361 ✗ if (newmode == KGC_GEN) /* entering generational mode? */
1362 ✗ entergen(L, g);
1363 else
1364 ✗ enterinc(g); /* entering incremental mode */
1365 }
1366 594 g->lastatomic = 0;
1367 594 }
1368
1369
1370 /*
1371 ** Does a full collection in generational mode.
1372 */
1373 ✗ static lu_mem fullgen (lua_State *L, global_State *g) {
1374 ✗ enterinc(g);
1375 ✗ return entergen(L, g);
1376 }
1377
1378
1379 /*
1380 ** Does a major collection after last collection was a "bad collection".
1381 **
1382 ** When the program is building a big structure, it allocates lots of
1383 ** memory but generates very little garbage. In those scenarios,
1384 ** the generational mode just wastes time doing small collections, and
1385 ** major collections are frequently what we call a "bad collection", a
1386 ** collection that frees too few objects. To avoid the cost of switching
1387 ** between generational mode and the incremental mode needed for full
1388 ** (major) collections, the collector tries to stay in incremental mode
1389 ** after a bad collection, and to switch back to generational mode only
1390 ** after a "good" collection (one that traverses less than 9/8 objects
1391 ** of the previous one).
1392 ** The collector must choose whether to stay in incremental mode or to
1393 ** switch back to generational mode before sweeping. At this point, it
1394 ** does not know the real memory in use, so it cannot use memory to
1395 ** decide whether to return to generational mode. Instead, it uses the
1396 ** number of objects traversed (returned by 'atomic') as a proxy. The
1397 ** field 'g->lastatomic' keeps this count from the last collection.
1398 ** ('g->lastatomic != 0' also means that the last collection was bad.)
1399 */
1400 ✗ static void stepgenfull (lua_State *L, global_State *g) {
1401 lu_mem newatomic; /* count of traversed objects */
1402 ✗ lu_mem lastatomic = g->lastatomic; /* count from last collection */
1403 ✗ if (g->gckind == KGC_GEN) /* still in generational mode? */
1404 ✗ enterinc(g); /* enter incremental mode */
1405 ✗ luaC_runtilstate(L, bitmask(GCSpropagate)); /* start new cycle */
1406 ✗ newatomic = atomic(L); /* mark everybody */
1407 ✗ if (newatomic < lastatomic + (lastatomic >> 3)) { /* good collection? */
1408 ✗ atomic2gen(L, g); /* return to generational mode */
1409 ✗ setminordebt(g);
1410 }
1411 else { /* another bad collection; stay in incremental mode */
1412 ✗ g->GCestimate = gettotalbytes(g); /* first estimate */;
1413 ✗ entersweep(L);
1414 ✗ luaC_runtilstate(L, bitmask(GCSpause)); /* finish collection */
1415 ✗ setpause(g);
1416 ✗ g->lastatomic = newatomic;
1417 }
1418 ✗ }
1419
1420
1421 /*
1422 ** Does a generational "step".
1423 ** Usually, this means doing a minor collection and setting the debt to
1424 ** make another collection when memory grows 'genminormul'% larger.
1425 **
1426 ** However, there are exceptions. If memory grows 'genmajormul'%
1427 ** larger than it was at the end of the last major collection (kept
1428 ** in 'g->GCestimate'), the function does a major collection. At the
1429 ** end, it checks whether the major collection was able to free a
1430 ** decent amount of memory (at least half the growth in memory since
1431 ** previous major collection). If so, the collector keeps its state,
1432 ** and the next collection will probably be minor again. Otherwise,
1433 ** we have what we call a "bad collection". In that case, set the field
1434 ** 'g->lastatomic' to signal that fact, so that the next collection will
1435 ** go to 'stepgenfull'.
1436 **
1437 ** 'GCdebt <= 0' means an explicit call to GC step with "size" zero;
1438 ** in that case, do a minor collection.
1439 */
1440 ✗ static void genstep (lua_State *L, global_State *g) {
1441 ✗ if (g->lastatomic != 0) /* last collection was a bad one? */
1442 ✗ stepgenfull(L, g); /* do a full step */
1443 else {
1444 ✗ lu_mem majorbase = g->GCestimate; /* memory after last major collection */
1445 ✗ lu_mem majorinc = (majorbase / 100) * getgcparam(g->genmajormul);
1446 ✗ if (g->GCdebt > 0 && gettotalbytes(g) > majorbase + majorinc) {
1447 ✗ lu_mem numobjs = fullgen(L, g); /* do a major collection */
1448 ✗ if (gettotalbytes(g) < majorbase + (majorinc / 2)) {
1449 /* collected at least half of memory growth since last major
1450 collection; keep doing minor collections. */
1451 lua_assert(g->lastatomic == 0);
1452 }
1453 else { /* bad collection */
1454 ✗ g->lastatomic = numobjs; /* signal that last collection was bad */
1455 ✗ setpause(g); /* do a long wait for next (major) collection */
1456 }
1457 }
1458 else { /* regular case; do a minor collection */
1459 ✗ youngcollection(L, g);
1460 ✗ setminordebt(g);
1461 ✗ g->GCestimate = majorbase; /* preserve base value */
1462 }
1463 }
1464 lua_assert(isdecGCmodegen(g));
1465 ✗ }
1466
1467 /* }====================================================== */
1468
1469
1470 /*
1471 ** {======================================================
1472 ** GC control
1473 ** =======================================================
1474 */
1475
1476
1477 /*
1478 ** Enter first sweep phase.
1479 ** The call to 'sweeptolive' makes the pointer point to an object
1480 ** inside the list (instead of to the header), so that the real sweep do
1481 ** not need to skip objects created between "now" and the start of the
1482 ** real sweep.
1483 */
1484 891 static void entersweep (lua_State *L) {
1485 891 global_State *g = G(L);
1486 891 g->gcstate = GCSswpallgc;
1487 lua_assert(g->sweepgc == NULL);
1488 891 g->sweepgc = sweeptolive(L, &g->allgc);
1489 891 }
1490
1491
1492 /*
1493 ** Delete all objects in list 'p' until (but not including) object
1494 ** 'limit'.
1495 */
1496 594 static void deletelist (lua_State *L, GCObject *p, GCObject *limit) {
1497
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 71219 while (p != limit) {
1498 70625 GCObject *next = p->next;
1499 70625 freeobj(L, p);
1500 70625 p = next;
1501 }
1502 594 }
1503
1504
1505 /*
1506 ** Call all finalizers of the objects in the given Lua state, and
1507 ** then free all objects, except for the main thread.
1508 */
1509 297 void luaC_freeallobjects (lua_State *L) {
1510 297 global_State *g = G(L);
1511 297 g->gcstp = GCSTPCLS; /* no extra finalizers after here */
1512 297 luaC_changemode(L, KGC_INC);
1513 297 separatetobefnz(g, 1); /* separate all objects with finalizers */
1514 lua_assert(g->finobj == NULL);
1515 297 callallpendingfinalizers(L);
1516 297 deletelist(L, g->allgc, obj2gco(g->mainthread));
1517 lua_assert(g->finobj == NULL); /* no new finalizers */
1518 297 deletelist(L, g->fixedgc, NULL); /* collect fixed objects */
1519 lua_assert(g->strt.nuse == 0);
1520 297 }
1521
1522
1523 891 static lu_mem atomic (lua_State *L) {
1524 891 global_State *g = G(L);
1525 891 lu_mem work = 0;
1526 GCObject *origweak, *origall;
1527 891 GCObject *grayagain = g->grayagain; /* save original list */
1528 891 g->grayagain = NULL;
1529 lua_assert(g->ephemeron == NULL && g->weak == NULL);
1530 lua_assert(!iswhite(g->mainthread));
1531 891 g->gcstate = GCSatomic;
1532
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 891 markobject(g, L); /* mark running thread */
1533 /* registry and global metatables may be changed by API */
1534
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 891 markvalue(g, &g->l_registry);
1535 891 markmt(g); /* mark global metatables */
1536 891 work += propagateall(g); /* empties 'gray' list */
1537 /* remark occasional upvalues of (maybe) dead threads */
1538 891 work += remarkupvals(g);
1539 891 work += propagateall(g); /* propagate changes */
1540 891 g->gray = grayagain;
1541 891 work += propagateall(g); /* traverse 'grayagain' list */
1542 891 convergeephemerons(g);
1543 /* at this point, all strongly accessible objects are marked. */
1544 /* Clear values from weak tables, before checking finalizers */
1545 891 clearbyvalues(g, g->weak, NULL);
1546 891 clearbyvalues(g, g->allweak, NULL);
1547 891 origweak = g->weak; origall = g->allweak;
1548 891 separatetobefnz(g, 0); /* separate objects to be finalized */
1549 891 work += markbeingfnz(g); /* mark objects that will be finalized */
1550 891 work += propagateall(g); /* remark, to propagate 'resurrection' */
1551 891 convergeephemerons(g);
1552 /* at this point, all resurrected objects are marked. */
1553 /* remove dead objects from weak tables */
1554 891 clearbykeys(g, g->ephemeron); /* clear keys from all ephemeron tables */
1555 891 clearbykeys(g, g->allweak); /* clear keys from all 'allweak' tables */
1556 /* clear values from resurrected weak tables */
1557 891 clearbyvalues(g, g->weak, origweak);
1558 891 clearbyvalues(g, g->allweak, origall);
1559 891 luaS_clearcache(g);
1560 891 g->currentwhite = cast_byte(otherwhite(g)); /* flip current white */
1561 lua_assert(g->gray == NULL);
1562 891 return work; /* estimate of slots marked by 'atomic' */
1563 }
1564
1565
1566 5643 static int sweepstep (lua_State *L, global_State *g,
1567 int nextstate, GCObject **nextlist) {
1568
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 5643 if (g->sweepgc) {
1569 2970 l_mem olddebt = g->GCdebt;
1570 int count;
1571 2970 g->sweepgc = sweeplist(L, g->sweepgc, GCSWEEPMAX, &count);
1572 2970 g->GCestimate += g->GCdebt - olddebt; /* update estimate */
1573 2970 return count;
1574 }
1575 else { /* enter next state */
1576 2673 g->gcstate = nextstate;
1577 2673 g->sweepgc = nextlist;
1578 2673 return 0; /* no work done */
1579 }
1580 }
1581
1582
1583 40392 static lu_mem singlestep (lua_State *L) {
1584 40392 global_State *g = G(L);
1585 lu_mem work;
1586 lua_assert(!g->gcstopem); /* collector is not reentrant */
1587 40392 g->gcstopem = 1; /* no emergency collections while collecting */
1588
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 40392 switch (g->gcstate) {
1589
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 891 case GCSpause: {
1590 891 restartcollection(g);
1591 891 g->gcstate = GCSpropagate;
1592 891 work = 1;
1593 891 break;
1594 }
1595
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 31185 case GCSpropagate: {
1596
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 31185 if (g->gray == NULL) { /* no more gray objects? */
1597 891 g->gcstate = GCSenteratomic; /* finish propagate phase */
1598 891 work = 0;
1599 }
1600 else
1601 30294 work = propagatemark(g); /* traverse one gray object */
1602 31185 break;
1603 }
1604
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 891 case GCSenteratomic: {
1605 891 work = atomic(L); /* work is what was traversed by 'atomic' */
1606 891 entersweep(L);
1607 891 g->GCestimate = gettotalbytes(g); /* first estimate */;
1608 891 break;
1609 }
1610
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 2079 case GCSswpallgc: { /* sweep "regular" objects */
1611 2079 work = sweepstep(L, g, GCSswpfinobj, &g->finobj);
1612 2079 break;
1613 }
1614
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 1782 case GCSswpfinobj: { /* sweep objects with finalizers */
1615 1782 work = sweepstep(L, g, GCSswptobefnz, &g->tobefnz);
1616 1782 break;
1617 }
1618
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 1782 case GCSswptobefnz: { /* sweep objects to be finalized */
1619 1782 work = sweepstep(L, g, GCSswpend, NULL);
1620 1782 break;
1621 }
1622
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 891 case GCSswpend: { /* finish sweeps */
1623 891 checkSizes(L, g);
1624 891 g->gcstate = GCScallfin;
1625 891 work = 0;
1626 891 break;
1627 }
1628
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 891 case GCScallfin: { /* call remaining finalizers */
1629
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 891 if (g->tobefnz && !g->gcemergency) {
1630 ✗ g->gcstopem = 0; /* ok collections during finalizers */
1631 ✗ work = runafewfinalizers(L, GCFINMAX) * GCFINALIZECOST;
1632 }
1633 else { /* emergency mode or no more finalizers */
1634 891 g->gcstate = GCSpause; /* finish collection */
1635 891 work = 0;
1636 }
1637 891 break;
1638 }
1639 ✗ default: lua_assert(0); return 0;
1640 }
1641 40392 g->gcstopem = 0;
1642 40392 return work;
1643 }
1644
1645
1646 /*
1647 ** advances the garbage collector until it reaches a state allowed
1648 ** by 'statemask'
1649 */
1650 891 void luaC_runtilstate (lua_State *L, int statesmask) {
1651 891 global_State *g = G(L);
1652
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 24354 while (!testbit(statesmask, g->gcstate))
1653 23463 singlestep(L);
1654 891 }
1655
1656
1657
1658 /*
1659 ** Performs a basic incremental step. The debt and step size are
1660 ** converted from bytes to "units of work"; then the function loops
1661 ** running single steps until adding that many units of work or
1662 ** finishing a cycle (pause state). Finally, it sets the debt that
1663 ** controls when next step will be performed.
1664 */
1665 594 static void incstep (lua_State *L, global_State *g) {
1666 594 int stepmul = (getgcparam(g->gcstepmul) | 1); /* avoid division by 0 */
1667 594 l_mem debt = (g->GCdebt / WORK2MEM) * stepmul;
1668 594 l_mem stepsize = (g->gcstepsize <= log2maxs(l_mem))
1669 594 ? ((cast(l_mem, 1) << g->gcstepsize) / WORK2MEM) * stepmul
1670
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 594 : MAX_LMEM; /* overflow; keep maximum value */
1671 do { /* repeat until pause or enough "credit" (negative debt) */
1672 16929 lu_mem work = singlestep(L); /* perform one single step */
1673 16929 debt -= work;
1674
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 16929 } while (debt > -stepsize && g->gcstate != GCSpause);
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 594 if (g->gcstate == GCSpause)
1676 594 setpause(g); /* pause until next cycle */
1677 else {
1678 ✗ debt = (debt / stepmul) * WORK2MEM; /* convert 'work units' to bytes */
1679 ✗ luaE_setdebt(g, debt);
1680 }
1681 594 }
1682
1683 /*
1684 ** Performs a basic GC step if collector is running. (If collector is
1685 ** not running, set a reasonable debt to avoid it being called at
1686 ** every single check.)
1687 */
1688 594 void luaC_step (lua_State *L) {
1689 594 global_State *g = G(L);
1690
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 594 if (!gcrunning(g)) /* not running? */
1691 ✗ luaE_setdebt(g, -2000);
1692 else {
1693
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 594 if(isdecGCmodegen(g))
1694 ✗ genstep(L, g);
1695 else
1696 594 incstep(L, g);
1697 }
1698 594 }
1699
1700
1701 /*
1702 ** Perform a full collection in incremental mode.
1703 ** Before running the collection, check 'keepinvariant'; if it is true,
1704 ** there may be some objects marked as black, so the collector has
1705 ** to sweep all objects to turn them back to white (as white has not
1706 ** changed, nothing will be collected).
1707 */
1708 297 static void fullinc (lua_State *L, global_State *g) {
1709
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 297 if (keepinvariant(g)) /* black objects? */
1710 ✗ entersweep(L); /* sweep everything to turn them back to white */
1711 /* finish any pending sweep phase to start a new cycle */
1712 297 luaC_runtilstate(L, bitmask(GCSpause));
1713 297 luaC_runtilstate(L, bitmask(GCScallfin)); /* run up to finalizers */
1714 /* estimate must be correct after a full GC cycle */
1715 lua_assert(g->GCestimate == gettotalbytes(g));
1716 297 luaC_runtilstate(L, bitmask(GCSpause)); /* finish collection */
1717 297 setpause(g);
1718 297 }
1719
1720
1721 /*
1722 ** Performs a full GC cycle; if 'isemergency', set a flag to avoid
1723 ** some operations which could change the interpreter state in some
1724 ** unexpected ways (running finalizers and shrinking some structures).
1725 */
1726 297 void luaC_fullgc (lua_State *L, int isemergency) {
1727 297 global_State *g = G(L);
1728 lua_assert(!g->gcemergency);
1729 297 g->gcemergency = isemergency; /* set flag */
1730
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 297 if (g->gckind == KGC_INC)
1731 297 fullinc(L, g);
1732 else
1733 ✗ fullgen(L, g);
1734 297 g->gcemergency = 0;
1735 297 }
1736
1737 /* }====================================================== */
1738
1739
1740