1 /* $NetBSD: lgc.c,v 1.4 2015/10/08 13:21:00 mbalmer Exp $ */
4 ** Id: lgc.c,v 2.205 2015/03/25 13:42:19 roberto Exp
6 ** See Copyright Notice in lua.h
34 ** internal state for collector while inside the atomic phase. The
35 ** collector should never be in this state while running regular code.
37 #define GCSinsideatomic (GCSpause + 1)
40 ** cost of sweeping one element (the size of a small object divided
41 ** by some adjust for the sweep speed)
43 #define GCSWEEPCOST ((sizeof(TString) + 4) / 4)
45 /* maximum number of elements to sweep in each single step */
46 #define GCSWEEPMAX (cast_int((GCSTEPSIZE / GCSWEEPCOST) / 4))
48 /* cost of calling one finalizer */
49 #define GCFINALIZECOST GCSWEEPCOST
53 ** macro to adjust 'stepmul': 'stepmul' is actually used like
54 ** 'stepmul / STEPMULADJ' (value chosen by tests)
56 #define STEPMULADJ 200
60 ** macro to adjust 'pause': 'pause' is actually used like
61 ** 'pause / PAUSEADJ' (value chosen by tests)
67 ** 'makewhite' erases all color bits then sets only the current white
70 #define maskcolors (~(bitmask(BLACKBIT) | WHITEBITS))
71 #define makewhite(g,x) \
72 (x->marked = cast_byte((x->marked & maskcolors) | luaC_white(g)))
74 #define white2gray(x) resetbits(x->marked, WHITEBITS)
75 #define black2gray(x) resetbit(x->marked, BLACKBIT)
78 #define valiswhite(x) (iscollectable(x) && iswhite(gcvalue(x)))
80 #define checkdeadkey(n) lua_assert(!ttisdeadkey(gkey(n)) || ttisnil(gval(n)))
83 #define checkconsistency(obj) \
84 lua_longassert(!iscollectable(obj) || righttt(obj))
87 #define markvalue(g,o) { checkconsistency(o); \
88 if (valiswhite(o)) reallymarkobject(g,gcvalue(o)); }
90 #define markobject(g,t) { if (iswhite(t)) reallymarkobject(g, obj2gco(t)); }
93 ** mark an object that can be NULL (either because it is really optional,
94 ** or it was stripped as debug info, or inside an uncompleted structure)
96 #define markobjectN(g,t) { if (t) markobject(g,t); }
98 static void reallymarkobject (global_State
*g
, GCObject
*o
);
102 ** {======================================================
104 ** =======================================================
109 ** one after last element in a hash array
111 #define gnodelast(h) gnode(h, cast(size_t, sizenode(h)))
115 ** link collectable object 'o' into list pointed by 'p'
117 #define linkgclist(o,p) ((o)->gclist = (p), (p) = obj2gco(o))
121 ** if key is not marked, mark its entry as dead (therefore removing it
124 static void removeentry (Node
*n
) {
125 lua_assert(ttisnil(gval(n
)));
126 if (valiswhite(gkey(n
)))
127 setdeadvalue(wgkey(n
)); /* unused and unmarked key; remove it */
132 ** tells whether a key or value can be cleared from a weak
133 ** table. Non-collectable objects are never removed from weak
134 ** tables. Strings behave as 'values', so are never removed too. for
135 ** other objects: if really collected, cannot keep them; for objects
136 ** being finalized, keep them in keys, but not in values
138 static int iscleared (global_State
*g
, const TValue
*o
) {
139 if (!iscollectable(o
)) return 0;
140 else if (ttisstring(o
)) {
141 markobject(g
, tsvalue(o
)); /* strings are 'values', so are never weak */
144 else return iswhite(gcvalue(o
));
149 ** barrier that moves collector forward, that is, mark the white object
150 ** being pointed by a black object. (If in sweep phase, clear the black
151 ** object to white [sweep it] to avoid other barrier calls for this
154 void luaC_barrier_ (lua_State
*L
, GCObject
*o
, GCObject
*v
) {
155 global_State
*g
= G(L
);
156 lua_assert(isblack(o
) && iswhite(v
) && !isdead(g
, v
) && !isdead(g
, o
));
157 if (keepinvariant(g
)) /* must keep invariant? */
158 reallymarkobject(g
, v
); /* restore invariant */
159 else { /* sweep phase */
160 lua_assert(issweepphase(g
));
161 makewhite(g
, o
); /* mark main obj. as white to avoid other barriers */
167 ** barrier that moves collector backward, that is, mark the black object
168 ** pointing to a white object as gray again.
170 void luaC_barrierback_ (lua_State
*L
, Table
*t
) {
171 global_State
*g
= G(L
);
172 lua_assert(isblack(t
) && !isdead(g
, t
));
173 black2gray(t
); /* make table gray (again) */
174 linkgclist(t
, g
->grayagain
);
179 ** barrier for assignments to closed upvalues. Because upvalues are
180 ** shared among closures, it is impossible to know the color of all
181 ** closures pointing to it. So, we assume that the object being assigned
184 void luaC_upvalbarrier_ (lua_State
*L
, UpVal
*uv
) {
185 global_State
*g
= G(L
);
186 GCObject
*o
= gcvalue(uv
->v
);
187 lua_assert(!upisopen(uv
)); /* ensured by macro luaC_upvalbarrier */
188 if (keepinvariant(g
))
193 void luaC_fix (lua_State
*L
, GCObject
*o
) {
194 global_State
*g
= G(L
);
195 lua_assert(g
->allgc
== o
); /* object must be 1st in 'allgc' list! */
196 white2gray(o
); /* they will be gray forever */
197 g
->allgc
= o
->next
; /* remove object from 'allgc' list */
198 o
->next
= g
->fixedgc
; /* link it to 'fixedgc' list */
204 ** create a new collectable object (with given type and size) and link
205 ** it to 'allgc' list.
207 GCObject
*luaC_newobj (lua_State
*L
, int tt
, size_t sz
) {
208 global_State
*g
= G(L
);
209 GCObject
*o
= cast(GCObject
*, luaM_newobject(L
, novariant(tt
), sz
));
210 o
->marked
= luaC_white(g
);
217 /* }====================================================== */
222 ** {======================================================
224 ** =======================================================
229 ** mark an object. Userdata, strings, and closed upvalues are visited
230 ** and turned black here. Other objects are marked gray and added
231 ** to appropriate list to be visited (and turned black) later. (Open
232 ** upvalues are already linked in 'headuv' list.)
234 static void reallymarkobject (global_State
*g
, GCObject
*o
) {
240 g
->GCmemtrav
+= sizelstring(gco2ts(o
)->shrlen
);
245 g
->GCmemtrav
+= sizelstring(gco2ts(o
)->u
.lnglen
);
248 case LUA_TUSERDATA
: {
250 markobjectN(g
, gco2u(o
)->metatable
); /* mark its metatable */
252 g
->GCmemtrav
+= sizeudata(gco2u(o
));
253 getuservalue(g
->mainthread
, gco2u(o
), &uvalue
);
254 if (valiswhite(&uvalue
)) { /* markvalue(g, &uvalue); */
255 o
= gcvalue(&uvalue
);
261 linkgclist(gco2lcl(o
), g
->gray
);
265 linkgclist(gco2ccl(o
), g
->gray
);
269 linkgclist(gco2t(o
), g
->gray
);
273 linkgclist(gco2th(o
), g
->gray
);
277 linkgclist(gco2p(o
), g
->gray
);
280 default: lua_assert(0); break;
286 ** mark metamethods for basic types
288 static void markmt (global_State
*g
) {
290 for (i
=0; i
< LUA_NUMTAGS
; i
++)
291 markobjectN(g
, g
->mt
[i
]);
296 ** mark all objects in list of being-finalized
298 static void markbeingfnz (global_State
*g
) {
300 for (o
= g
->tobefnz
; o
!= NULL
; o
= o
->next
)
306 ** Mark all values stored in marked open upvalues from non-marked threads.
307 ** (Values from marked threads were already marked when traversing the
308 ** thread.) Remove from the list threads that no longer have upvalues and
309 ** not-marked threads.
311 static void remarkupvals (global_State
*g
) {
313 lua_State
**p
= &g
->twups
;
314 while ((thread
= *p
) != NULL
) {
315 lua_assert(!isblack(thread
)); /* threads are never black */
316 if (isgray(thread
) && thread
->openupval
!= NULL
)
317 p
= &thread
->twups
; /* keep marked thread with upvalues in the list */
318 else { /* thread is not marked or without upvalues */
320 *p
= thread
->twups
; /* remove thread from the list */
321 thread
->twups
= thread
; /* mark that it is out of list */
322 for (uv
= thread
->openupval
; uv
!= NULL
; uv
= uv
->u
.open
.next
) {
323 if (uv
->u
.open
.touched
) {
324 markvalue(g
, uv
->v
); /* remark upvalue's value */
325 uv
->u
.open
.touched
= 0;
334 ** mark root set and reset all gray lists, to start a new collection
336 static void restartcollection (global_State
*g
) {
337 g
->gray
= g
->grayagain
= NULL
;
338 g
->weak
= g
->allweak
= g
->ephemeron
= NULL
;
339 markobject(g
, g
->mainthread
);
340 markvalue(g
, &g
->l_registry
);
342 markbeingfnz(g
); /* mark any finalizing object left from previous cycle */
345 /* }====================================================== */
349 ** {======================================================
350 ** Traverse functions
351 ** =======================================================
355 ** Traverse a table with weak values and link it to proper list. During
356 ** propagate phase, keep it in 'grayagain' list, to be revisited in the
357 ** atomic phase. In the atomic phase, if table has any white value,
358 ** put it in 'weak' list, to be cleared.
360 static void traverseweakvalue (global_State
*g
, Table
*h
) {
361 Node
*n
, *limit
= gnodelast(h
);
362 /* if there is array part, assume it may have white values (it is not
363 worth traversing it now just to check) */
364 int hasclears
= (h
->sizearray
> 0);
365 for (n
= gnode(h
, 0); n
< limit
; n
++) { /* traverse hash part */
367 if (ttisnil(gval(n
))) /* entry is empty? */
368 removeentry(n
); /* remove it */
370 lua_assert(!ttisnil(gkey(n
)));
371 markvalue(g
, gkey(n
)); /* mark key */
372 if (!hasclears
&& iscleared(g
, gval(n
))) /* is there a white value? */
373 hasclears
= 1; /* table will have to be cleared */
376 if (g
->gcstate
== GCSpropagate
)
377 linkgclist(h
, g
->grayagain
); /* must retraverse it in atomic phase */
379 linkgclist(h
, g
->weak
); /* has to be cleared later */
384 ** Traverse an ephemeron table and link it to proper list. Returns true
385 ** iff any object was marked during this traversal (which implies that
386 ** convergence has to continue). During propagation phase, keep table
387 ** in 'grayagain' list, to be visited again in the atomic phase. In
388 ** the atomic phase, if table has any white->white entry, it has to
389 ** be revisited during ephemeron convergence (as that key may turn
390 ** black). Otherwise, if it has any white key, table has to be cleared
391 ** (in the atomic phase).
393 static int traverseephemeron (global_State
*g
, Table
*h
) {
394 int marked
= 0; /* true if an object is marked in this traversal */
395 int hasclears
= 0; /* true if table has white keys */
396 int hasww
= 0; /* true if table has entry "white-key -> white-value" */
397 Node
*n
, *limit
= gnodelast(h
);
399 /* traverse array part */
400 for (i
= 0; i
< h
->sizearray
; i
++) {
401 if (valiswhite(&h
->array
[i
])) {
403 reallymarkobject(g
, gcvalue(&h
->array
[i
]));
406 /* traverse hash part */
407 for (n
= gnode(h
, 0); n
< limit
; n
++) {
409 if (ttisnil(gval(n
))) /* entry is empty? */
410 removeentry(n
); /* remove it */
411 else if (iscleared(g
, gkey(n
))) { /* key is not marked (yet)? */
412 hasclears
= 1; /* table must be cleared */
413 if (valiswhite(gval(n
))) /* value not marked yet? */
414 hasww
= 1; /* white-white entry */
416 else if (valiswhite(gval(n
))) { /* value not marked yet? */
418 reallymarkobject(g
, gcvalue(gval(n
))); /* mark it now */
421 /* link table into proper list */
422 if (g
->gcstate
== GCSpropagate
)
423 linkgclist(h
, g
->grayagain
); /* must retraverse it in atomic phase */
424 else if (hasww
) /* table has white->white entries? */
425 linkgclist(h
, g
->ephemeron
); /* have to propagate again */
426 else if (hasclears
) /* table has white keys? */
427 linkgclist(h
, g
->allweak
); /* may have to clean white keys */
432 static void traversestrongtable (global_State
*g
, Table
*h
) {
433 Node
*n
, *limit
= gnodelast(h
);
435 for (i
= 0; i
< h
->sizearray
; i
++) /* traverse array part */
436 markvalue(g
, &h
->array
[i
]);
437 for (n
= gnode(h
, 0); n
< limit
; n
++) { /* traverse hash part */
439 if (ttisnil(gval(n
))) /* entry is empty? */
440 removeentry(n
); /* remove it */
442 lua_assert(!ttisnil(gkey(n
)));
443 markvalue(g
, gkey(n
)); /* mark key */
444 markvalue(g
, gval(n
)); /* mark value */
450 static lu_mem
traversetable (global_State
*g
, Table
*h
) {
451 const char *weakkey
, *weakvalue
;
452 const TValue
*mode
= gfasttm(g
, h
->metatable
, TM_MODE
);
453 markobjectN(g
, h
->metatable
);
454 if (mode
&& ttisstring(mode
) && /* is there a weak mode? */
455 ((weakkey
= strchr(svalue(mode
), 'k')),
456 (weakvalue
= strchr(svalue(mode
), 'v')),
457 (weakkey
|| weakvalue
))) { /* is really weak? */
458 black2gray(h
); /* keep table gray */
459 if (!weakkey
) /* strong keys? */
460 traverseweakvalue(g
, h
);
461 else if (!weakvalue
) /* strong values? */
462 traverseephemeron(g
, h
);
464 linkgclist(h
, g
->allweak
); /* nothing to traverse now */
467 traversestrongtable(g
, h
);
468 return sizeof(Table
) + sizeof(TValue
) * h
->sizearray
+
469 sizeof(Node
) * cast(size_t, sizenode(h
));
474 ** Traverse a prototype. (While a prototype is being build, its
475 ** arrays can be larger than needed; the extra slots are filled with
476 ** NULL, so the use of 'markobjectN')
478 static int traverseproto (global_State
*g
, Proto
*f
) {
480 if (f
->cache
&& iswhite(f
->cache
))
481 f
->cache
= NULL
; /* allow cache to be collected */
482 markobjectN(g
, f
->source
);
483 for (i
= 0; i
< f
->sizek
; i
++) /* mark literals */
484 markvalue(g
, &f
->k
[i
]);
485 for (i
= 0; i
< f
->sizeupvalues
; i
++) /* mark upvalue names */
486 markobjectN(g
, f
->upvalues
[i
].name
);
487 for (i
= 0; i
< f
->sizep
; i
++) /* mark nested protos */
488 markobjectN(g
, f
->p
[i
]);
489 for (i
= 0; i
< f
->sizelocvars
; i
++) /* mark local-variable names */
490 markobjectN(g
, f
->locvars
[i
].varname
);
491 return sizeof(Proto
) + sizeof(Instruction
) * f
->sizecode
+
492 sizeof(Proto
*) * f
->sizep
+
493 sizeof(TValue
) * f
->sizek
+
494 sizeof(int) * f
->sizelineinfo
+
495 sizeof(LocVar
) * f
->sizelocvars
+
496 sizeof(Upvaldesc
) * f
->sizeupvalues
;
500 static lu_mem
traverseCclosure (global_State
*g
, CClosure
*cl
) {
502 for (i
= 0; i
< cl
->nupvalues
; i
++) /* mark its upvalues */
503 markvalue(g
, &cl
->upvalue
[i
]);
504 return sizeCclosure(cl
->nupvalues
);
508 ** open upvalues point to values in a thread, so those values should
509 ** be marked when the thread is traversed except in the atomic phase
510 ** (because then the value cannot be changed by the thread and the
511 ** thread may not be traversed again)
513 static lu_mem
traverseLclosure (global_State
*g
, LClosure
*cl
) {
515 markobjectN(g
, cl
->p
); /* mark its prototype */
516 for (i
= 0; i
< cl
->nupvalues
; i
++) { /* mark its upvalues */
517 UpVal
*uv
= cl
->upvals
[i
];
519 if (upisopen(uv
) && g
->gcstate
!= GCSinsideatomic
)
520 uv
->u
.open
.touched
= 1; /* can be marked in 'remarkupvals' */
525 return sizeLclosure(cl
->nupvalues
);
529 static lu_mem
traversethread (global_State
*g
, lua_State
*th
) {
532 return 1; /* stack not completely built yet */
533 lua_assert(g
->gcstate
== GCSinsideatomic
||
534 th
->openupval
== NULL
|| isintwups(th
));
535 for (; o
< th
->top
; o
++) /* mark live elements in the stack */
537 if (g
->gcstate
== GCSinsideatomic
) { /* final traversal? */
538 StkId lim
= th
->stack
+ th
->stacksize
; /* real end of stack */
539 for (; o
< lim
; o
++) /* clear not-marked stack slice */
541 /* 'remarkupvals' may have removed thread from 'twups' list */
542 if (!isintwups(th
) && th
->openupval
!= NULL
) {
543 th
->twups
= g
->twups
; /* link it back to the list */
547 else if (g
->gckind
!= KGC_EMERGENCY
)
548 luaD_shrinkstack(th
); /* do not change stack in emergency cycle */
549 return (sizeof(lua_State
) + sizeof(TValue
) * th
->stacksize
);
554 ** traverse one gray object, turning it to black (except for threads,
555 ** which are always gray).
557 static void propagatemark (global_State
*g
) {
559 GCObject
*o
= g
->gray
;
560 lua_assert(isgray(o
));
565 g
->gray
= h
->gclist
; /* remove from 'gray' list */
566 size
= traversetable(g
, h
);
570 LClosure
*cl
= gco2lcl(o
);
571 g
->gray
= cl
->gclist
; /* remove from 'gray' list */
572 size
= traverseLclosure(g
, cl
);
576 CClosure
*cl
= gco2ccl(o
);
577 g
->gray
= cl
->gclist
; /* remove from 'gray' list */
578 size
= traverseCclosure(g
, cl
);
582 lua_State
*th
= gco2th(o
);
583 g
->gray
= th
->gclist
; /* remove from 'gray' list */
584 linkgclist(th
, g
->grayagain
); /* insert into 'grayagain' list */
586 size
= traversethread(g
, th
);
591 g
->gray
= p
->gclist
; /* remove from 'gray' list */
592 size
= traverseproto(g
, p
);
595 default: lua_assert(0); return;
597 g
->GCmemtrav
+= size
;
601 static void propagateall (global_State
*g
) {
602 while (g
->gray
) propagatemark(g
);
606 static void convergeephemerons (global_State
*g
) {
610 GCObject
*next
= g
->ephemeron
; /* get ephemeron list */
611 g
->ephemeron
= NULL
; /* tables may return to this list when traversed */
613 while ((w
= next
) != NULL
) {
614 next
= gco2t(w
)->gclist
;
615 if (traverseephemeron(g
, gco2t(w
))) { /* traverse marked some value? */
616 propagateall(g
); /* propagate changes */
617 changed
= 1; /* will have to revisit all ephemeron tables */
623 /* }====================================================== */
627 ** {======================================================
629 ** =======================================================
634 ** clear entries with unmarked keys from all weaktables in list 'l' up
637 static void clearkeys (global_State
*g
, GCObject
*l
, GCObject
*f
) {
638 for (; l
!= f
; l
= gco2t(l
)->gclist
) {
640 Node
*n
, *limit
= gnodelast(h
);
641 for (n
= gnode(h
, 0); n
< limit
; n
++) {
642 if (!ttisnil(gval(n
)) && (iscleared(g
, gkey(n
)))) {
643 setnilvalue(gval(n
)); /* remove value ... */
644 removeentry(n
); /* and remove entry from table */
652 ** clear entries with unmarked values from all weaktables in list 'l' up
655 static void clearvalues (global_State
*g
, GCObject
*l
, GCObject
*f
) {
656 for (; l
!= f
; l
= gco2t(l
)->gclist
) {
658 Node
*n
, *limit
= gnodelast(h
);
660 for (i
= 0; i
< h
->sizearray
; i
++) {
661 TValue
*o
= &h
->array
[i
];
662 if (iscleared(g
, o
)) /* value was collected? */
663 setnilvalue(o
); /* remove value */
665 for (n
= gnode(h
, 0); n
< limit
; n
++) {
666 if (!ttisnil(gval(n
)) && iscleared(g
, gval(n
))) {
667 setnilvalue(gval(n
)); /* remove value ... */
668 removeentry(n
); /* and remove entry from table */
675 void luaC_upvdeccount (lua_State
*L
, UpVal
*uv
) {
676 lua_assert(uv
->refcount
> 0);
678 if (uv
->refcount
== 0 && !upisopen(uv
))
683 static void freeLclosure (lua_State
*L
, LClosure
*cl
) {
685 for (i
= 0; i
< cl
->nupvalues
; i
++) {
686 UpVal
*uv
= cl
->upvals
[i
];
688 luaC_upvdeccount(L
, uv
);
690 luaM_freemem(L
, cl
, sizeLclosure(cl
->nupvalues
));
694 static void freeobj (lua_State
*L
, GCObject
*o
) {
696 case LUA_TPROTO
: luaF_freeproto(L
, gco2p(o
)); break;
698 freeLclosure(L
, gco2lcl(o
));
702 luaM_freemem(L
, o
, sizeCclosure(gco2ccl(o
)->nupvalues
));
705 case LUA_TTABLE
: luaH_free(L
, gco2t(o
)); break;
706 case LUA_TTHREAD
: luaE_freethread(L
, gco2th(o
)); break;
707 case LUA_TUSERDATA
: luaM_freemem(L
, o
, sizeudata(gco2u(o
))); break;
709 luaS_remove(L
, gco2ts(o
)); /* remove it from hash table */
710 luaM_freemem(L
, o
, sizelstring(gco2ts(o
)->shrlen
));
713 luaM_freemem(L
, o
, sizelstring(gco2ts(o
)->u
.lnglen
));
716 default: lua_assert(0);
721 #define sweepwholelist(L,p) sweeplist(L,p,MAX_LUMEM)
722 static GCObject
**sweeplist (lua_State
*L
, GCObject
**p
, lu_mem count
);
726 ** sweep at most 'count' elements from a list of GCObjects erasing dead
727 ** objects, where a dead object is one marked with the old (non current)
728 ** white; change all non-dead objects back to white, preparing for next
729 ** collection cycle. Return where to continue the traversal or NULL if
732 static GCObject
**sweeplist (lua_State
*L
, GCObject
**p
, lu_mem count
) {
733 global_State
*g
= G(L
);
734 int ow
= otherwhite(g
);
735 int white
= luaC_white(g
); /* current white */
736 while (*p
!= NULL
&& count
-- > 0) {
738 int marked
= curr
->marked
;
739 if (isdeadm(ow
, marked
)) { /* is 'curr' dead? */
740 *p
= curr
->next
; /* remove 'curr' from list */
741 freeobj(L
, curr
); /* erase 'curr' */
743 else { /* change mark to 'white' */
744 curr
->marked
= cast_byte((marked
& maskcolors
) | white
);
745 p
= &curr
->next
; /* go to next element */
748 return (*p
== NULL
) ? NULL
: p
;
753 ** sweep a list until a live object (or end of list)
755 static GCObject
**sweeptolive (lua_State
*L
, GCObject
**p
, int *n
) {
760 p
= sweeplist(L
, p
, 1);
766 /* }====================================================== */
770 ** {======================================================
772 ** =======================================================
776 ** If possible, free concatenation buffer and shrink string table
778 static void checkSizes (lua_State
*L
, global_State
*g
) {
779 if (g
->gckind
!= KGC_EMERGENCY
) {
780 l_mem olddebt
= g
->GCdebt
;
781 luaZ_freebuffer(L
, &g
->buff
); /* free concatenation buffer */
782 if (g
->strt
.nuse
< g
->strt
.size
/ 4) /* string table too big? */
783 luaS_resize(L
, g
->strt
.size
/ 2); /* shrink it a little */
784 g
->GCestimate
+= g
->GCdebt
- olddebt
; /* update estimate */
789 static GCObject
*udata2finalize (global_State
*g
) {
790 GCObject
*o
= g
->tobefnz
; /* get first element */
791 lua_assert(tofinalize(o
));
792 g
->tobefnz
= o
->next
; /* remove it from 'tobefnz' list */
793 o
->next
= g
->allgc
; /* return it to 'allgc' list */
795 resetbit(o
->marked
, FINALIZEDBIT
); /* object is "normal" again */
797 makewhite(g
, o
); /* "sweep" object */
802 static void dothecall (lua_State
*L
, void *ud
) {
804 luaD_call(L
, L
->top
- 2, 0, 0);
808 static void GCTM (lua_State
*L
, int propagateerrors
) {
809 global_State
*g
= G(L
);
812 setgcovalue(L
, &v
, udata2finalize(g
));
813 tm
= luaT_gettmbyobj(L
, &v
, TM_GC
);
814 if (tm
!= NULL
&& ttisfunction(tm
)) { /* is there a finalizer? */
816 lu_byte oldah
= L
->allowhook
;
817 int running
= g
->gcrunning
;
818 L
->allowhook
= 0; /* stop debug hooks during GC metamethod */
819 g
->gcrunning
= 0; /* avoid GC steps */
820 setobj2s(L
, L
->top
, tm
); /* push finalizer... */
821 setobj2s(L
, L
->top
+ 1, &v
); /* ... and its argument */
822 L
->top
+= 2; /* and (next line) call the finalizer */
823 status
= luaD_pcall(L
, dothecall
, NULL
, savestack(L
, L
->top
- 2), 0);
824 L
->allowhook
= oldah
; /* restore hooks */
825 g
->gcrunning
= running
; /* restore state */
826 if (status
!= LUA_OK
&& propagateerrors
) { /* error while running __gc? */
827 if (status
== LUA_ERRRUN
) { /* is there an error object? */
828 const char *msg
= (ttisstring(L
->top
- 1))
831 luaO_pushfstring(L
, "error in __gc metamethod (%s)", msg
);
832 status
= LUA_ERRGCMM
; /* error in __gc metamethod */
834 luaD_throw(L
, status
); /* re-throw error */
841 ** call a few (up to 'g->gcfinnum') finalizers
843 static int runafewfinalizers (lua_State
*L
) {
844 global_State
*g
= G(L
);
846 lua_assert(!g
->tobefnz
|| g
->gcfinnum
> 0);
847 for (i
= 0; g
->tobefnz
&& i
< g
->gcfinnum
; i
++)
848 GCTM(L
, 1); /* call one finalizer */
849 g
->gcfinnum
= (!g
->tobefnz
) ? 0 /* nothing more to finalize? */
850 : g
->gcfinnum
* 2; /* else call a few more next time */
856 ** call all pending finalizers
858 static void callallpendingfinalizers (lua_State
*L
, int propagateerrors
) {
859 global_State
*g
= G(L
);
861 GCTM(L
, propagateerrors
);
866 ** find last 'next' field in list 'p' list (to add elements in its end)
868 static GCObject
**findlast (GCObject
**p
) {
876 ** move all unreachable objects (or 'all' objects) that need
877 ** finalization from list 'finobj' to list 'tobefnz' (to be finalized)
879 static void separatetobefnz (global_State
*g
, int all
) {
881 GCObject
**p
= &g
->finobj
;
882 GCObject
**lastnext
= findlast(&g
->tobefnz
);
883 while ((curr
= *p
) != NULL
) { /* traverse all finalizable objects */
884 lua_assert(tofinalize(curr
));
885 if (!(iswhite(curr
) || all
)) /* not being collected? */
886 p
= &curr
->next
; /* don't bother with it */
888 *p
= curr
->next
; /* remove 'curr' from 'finobj' list */
889 curr
->next
= *lastnext
; /* link at the end of 'tobefnz' list */
891 lastnext
= &curr
->next
;
898 ** if object 'o' has a finalizer, remove it from 'allgc' list (must
899 ** search the list to find it) and link it in 'finobj' list.
901 void luaC_checkfinalizer (lua_State
*L
, GCObject
*o
, Table
*mt
) {
902 global_State
*g
= G(L
);
903 if (tofinalize(o
) || /* obj. is already marked... */
904 gfasttm(g
, mt
, TM_GC
) == NULL
) /* or has no finalizer? */
905 return; /* nothing to be done */
906 else { /* move 'o' to 'finobj' list */
908 if (issweepphase(g
)) {
909 makewhite(g
, o
); /* "sweep" object 'o' */
910 if (g
->sweepgc
== &o
->next
) /* should not remove 'sweepgc' object */
911 g
->sweepgc
= sweeptolive(L
, g
->sweepgc
, NULL
); /* change 'sweepgc' */
913 /* search for pointer pointing to 'o' */
914 for (p
= &g
->allgc
; *p
!= o
; p
= &(*p
)->next
) { /* empty */ }
915 *p
= o
->next
; /* remove 'o' from 'allgc' list */
916 o
->next
= g
->finobj
; /* link it in 'finobj' list */
918 l_setbit(o
->marked
, FINALIZEDBIT
); /* mark it as such */
922 /* }====================================================== */
927 ** {======================================================
929 ** =======================================================
934 ** Set a reasonable "time" to wait before starting a new GC cycle; cycle
935 ** will start when memory use hits threshold. (Division by 'estimate'
936 ** should be OK: it cannot be zero (because Lua cannot even start with
937 ** less than PAUSEADJ bytes).
939 static void setpause (global_State
*g
) {
940 l_mem threshold
, debt
;
941 l_mem estimate
= g
->GCestimate
/ PAUSEADJ
; /* adjust 'estimate' */
942 lua_assert(estimate
> 0);
943 threshold
= (g
->gcpause
< MAX_LMEM
/ estimate
) /* overflow? */
944 ? estimate
* g
->gcpause
/* no overflow */
945 : MAX_LMEM
; /* overflow; truncate to maximum */
946 debt
= gettotalbytes(g
) - threshold
;
947 luaE_setdebt(g
, debt
);
952 ** Enter first sweep phase.
953 ** The call to 'sweeptolive' makes pointer point to an object inside
954 ** the list (instead of to the header), so that the real sweep do not
955 ** need to skip objects created between "now" and the start of the real
957 ** Returns how many objects it swept.
959 static int entersweep (lua_State
*L
) {
960 global_State
*g
= G(L
);
962 g
->gcstate
= GCSswpallgc
;
963 lua_assert(g
->sweepgc
== NULL
);
964 g
->sweepgc
= sweeptolive(L
, &g
->allgc
, &n
);
969 void luaC_freeallobjects (lua_State
*L
) {
970 global_State
*g
= G(L
);
971 separatetobefnz(g
, 1); /* separate all objects with finalizers */
972 lua_assert(g
->finobj
== NULL
);
973 callallpendingfinalizers(L
, 0);
974 lua_assert(g
->tobefnz
== NULL
);
975 g
->currentwhite
= WHITEBITS
; /* this "white" makes all objects look dead */
976 g
->gckind
= KGC_NORMAL
;
977 sweepwholelist(L
, &g
->finobj
);
978 sweepwholelist(L
, &g
->allgc
);
979 sweepwholelist(L
, &g
->fixedgc
); /* collect fixed objects */
980 lua_assert(g
->strt
.nuse
== 0);
984 static l_mem
atomic (lua_State
*L
) {
985 global_State
*g
= G(L
);
987 GCObject
*origweak
, *origall
;
988 GCObject
*grayagain
= g
->grayagain
; /* save original list */
989 lua_assert(g
->ephemeron
== NULL
&& g
->weak
== NULL
);
990 lua_assert(!iswhite(g
->mainthread
));
991 g
->gcstate
= GCSinsideatomic
;
992 g
->GCmemtrav
= 0; /* start counting work */
993 markobject(g
, L
); /* mark running thread */
994 /* registry and global metatables may be changed by API */
995 markvalue(g
, &g
->l_registry
);
996 markmt(g
); /* mark global metatables */
997 /* remark occasional upvalues of (maybe) dead threads */
999 propagateall(g
); /* propagate changes */
1000 work
= g
->GCmemtrav
; /* stop counting (do not recount 'grayagain') */
1001 g
->gray
= grayagain
;
1002 propagateall(g
); /* traverse 'grayagain' list */
1003 g
->GCmemtrav
= 0; /* restart counting */
1004 convergeephemerons(g
);
1005 /* at this point, all strongly accessible objects are marked. */
1006 /* Clear values from weak tables, before checking finalizers */
1007 clearvalues(g
, g
->weak
, NULL
);
1008 clearvalues(g
, g
->allweak
, NULL
);
1009 origweak
= g
->weak
; origall
= g
->allweak
;
1010 work
+= g
->GCmemtrav
; /* stop counting (objects being finalized) */
1011 separatetobefnz(g
, 0); /* separate objects to be finalized */
1012 g
->gcfinnum
= 1; /* there may be objects to be finalized */
1013 markbeingfnz(g
); /* mark objects that will be finalized */
1014 propagateall(g
); /* remark, to propagate 'resurrection' */
1015 g
->GCmemtrav
= 0; /* restart counting */
1016 convergeephemerons(g
);
1017 /* at this point, all resurrected objects are marked. */
1018 /* remove dead objects from weak tables */
1019 clearkeys(g
, g
->ephemeron
, NULL
); /* clear keys from all ephemeron tables */
1020 clearkeys(g
, g
->allweak
, NULL
); /* clear keys from all 'allweak' tables */
1021 /* clear values from resurrected weak tables */
1022 clearvalues(g
, g
->weak
, origweak
);
1023 clearvalues(g
, g
->allweak
, origall
);
1025 g
->currentwhite
= cast_byte(otherwhite(g
)); /* flip current white */
1026 work
+= g
->GCmemtrav
; /* complete counting */
1027 return work
; /* estimate of memory marked by 'atomic' */
1031 static lu_mem
sweepstep (lua_State
*L
, global_State
*g
,
1032 int nextstate
, GCObject
**nextlist
) {
1034 l_mem olddebt
= g
->GCdebt
;
1035 g
->sweepgc
= sweeplist(L
, g
->sweepgc
, GCSWEEPMAX
);
1036 g
->GCestimate
+= g
->GCdebt
- olddebt
; /* update estimate */
1037 if (g
->sweepgc
) /* is there still something to sweep? */
1038 return (GCSWEEPMAX
* GCSWEEPCOST
);
1040 /* else enter next state */
1041 g
->gcstate
= nextstate
;
1042 g
->sweepgc
= nextlist
;
1047 static lu_mem
singlestep (lua_State
*L
) {
1048 global_State
*g
= G(L
);
1049 switch (g
->gcstate
) {
1051 g
->GCmemtrav
= g
->strt
.size
* sizeof(GCObject
*);
1052 restartcollection(g
);
1053 g
->gcstate
= GCSpropagate
;
1054 return g
->GCmemtrav
;
1056 case GCSpropagate
: {
1058 lua_assert(g
->gray
);
1060 if (g
->gray
== NULL
) /* no more gray objects? */
1061 g
->gcstate
= GCSatomic
; /* finish propagate phase */
1062 return g
->GCmemtrav
; /* memory traversed in this step */
1067 propagateall(g
); /* make sure gray list is empty */
1068 work
= atomic(L
); /* work is what was traversed by 'atomic' */
1070 g
->GCestimate
= gettotalbytes(g
); /* first estimate */;
1071 return work
+ sw
* GCSWEEPCOST
;
1073 case GCSswpallgc
: { /* sweep "regular" objects */
1074 return sweepstep(L
, g
, GCSswpfinobj
, &g
->finobj
);
1076 case GCSswpfinobj
: { /* sweep objects with finalizers */
1077 return sweepstep(L
, g
, GCSswptobefnz
, &g
->tobefnz
);
1079 case GCSswptobefnz
: { /* sweep objects to be finalized */
1080 return sweepstep(L
, g
, GCSswpend
, NULL
);
1082 case GCSswpend
: { /* finish sweeps */
1083 makewhite(g
, g
->mainthread
); /* sweep main thread */
1085 g
->gcstate
= GCScallfin
;
1088 case GCScallfin
: { /* call remaining finalizers */
1089 if (g
->tobefnz
&& g
->gckind
!= KGC_EMERGENCY
) {
1090 int n
= runafewfinalizers(L
);
1091 return (n
* GCFINALIZECOST
);
1093 else { /* emergency mode or no more finalizers */
1094 g
->gcstate
= GCSpause
; /* finish collection */
1098 default: lua_assert(0); return 0;
1104 ** advances the garbage collector until it reaches a state allowed
1107 void luaC_runtilstate (lua_State
*L
, int statesmask
) {
1108 global_State
*g
= G(L
);
1109 while (!testbit(statesmask
, g
->gcstate
))
1115 ** get GC debt and convert it from Kb to 'work units' (avoid zero debt
1118 static l_mem
getdebt (global_State
*g
) {
1119 l_mem debt
= g
->GCdebt
;
1120 int stepmul
= g
->gcstepmul
;
1121 debt
= (debt
/ STEPMULADJ
) + 1;
1122 debt
= (debt
< MAX_LMEM
/ stepmul
) ? debt
* stepmul
: MAX_LMEM
;
1127 ** performs a basic GC step when collector is running
1129 void luaC_step (lua_State
*L
) {
1130 global_State
*g
= G(L
);
1131 l_mem debt
= getdebt(g
); /* GC deficit (be paid now) */
1132 if (!g
->gcrunning
) { /* not running? */
1133 luaE_setdebt(g
, -GCSTEPSIZE
* 10); /* avoid being called too often */
1136 do { /* repeat until pause or enough "credit" (negative debt) */
1137 lu_mem work
= singlestep(L
); /* perform one single step */
1139 } while (debt
> -GCSTEPSIZE
&& g
->gcstate
!= GCSpause
);
1140 if (g
->gcstate
== GCSpause
)
1141 setpause(g
); /* pause until next cycle */
1143 debt
= (debt
/ g
->gcstepmul
) * STEPMULADJ
; /* convert 'work units' to Kb */
1144 luaE_setdebt(g
, debt
);
1145 runafewfinalizers(L
);
1151 ** Performs a full GC cycle; if 'isemergency', set a flag to avoid
1152 ** some operations which could change the interpreter state in some
1153 ** unexpected ways (running finalizers and shrinking some structures).
1154 ** Before running the collection, check 'keepinvariant'; if it is true,
1155 ** there may be some objects marked as black, so the collector has
1156 ** to sweep all objects to turn them back to white (as white has not
1157 ** changed, nothing will be collected).
1159 void luaC_fullgc (lua_State
*L
, int isemergency
) {
1160 global_State
*g
= G(L
);
1161 lua_assert(g
->gckind
== KGC_NORMAL
);
1162 if (isemergency
) g
->gckind
= KGC_EMERGENCY
; /* set flag */
1163 if (keepinvariant(g
)) { /* black objects? */
1164 entersweep(L
); /* sweep everything to turn them back to white */
1166 /* finish any pending sweep phase to start a new cycle */
1167 luaC_runtilstate(L
, bitmask(GCSpause
));
1168 luaC_runtilstate(L
, ~bitmask(GCSpause
)); /* start new collection */
1169 luaC_runtilstate(L
, bitmask(GCScallfin
)); /* run up to finalizers */
1170 /* estimate must be correct after a full GC cycle */
1171 lua_assert(g
->GCestimate
== gettotalbytes(g
));
1172 luaC_runtilstate(L
, bitmask(GCSpause
)); /* finish collection */
1173 g
->gckind
= KGC_NORMAL
;
1177 /* }====================================================== */