diff options
Diffstat (limited to 'bruiser/lua-5.3.4/src/lgc.c')
| -rw-r--r-- | bruiser/lua-5.3.4/src/lgc.c | 1178 |
1 files changed, 1178 insertions, 0 deletions
diff --git a/bruiser/lua-5.3.4/src/lgc.c b/bruiser/lua-5.3.4/src/lgc.c new file mode 100644 index 0000000..ba2c19e --- /dev/null +++ b/bruiser/lua-5.3.4/src/lgc.c @@ -0,0 +1,1178 @@ +/* +** $Id: lgc.c,v 2.215 2016/12/22 13:08:50 roberto Exp $ +** Garbage Collector +** See Copyright Notice in lua.h +*/ + +#define lgc_c +#define LUA_CORE + +#include "lprefix.h" + + +#include <string.h> + +#include "lua.h" + +#include "ldebug.h" +#include "ldo.h" +#include "lfunc.h" +#include "lgc.h" +#include "lmem.h" +#include "lobject.h" +#include "lstate.h" +#include "lstring.h" +#include "ltable.h" +#include "ltm.h" + + +/* +** internal state for collector while inside the atomic phase. The +** collector should never be in this state while running regular code. +*/ +#define GCSinsideatomic (GCSpause + 1) + +/* +** cost of sweeping one element (the size of a small object divided +** by some adjust for the sweep speed) +*/ +#define GCSWEEPCOST ((sizeof(TString) + 4) / 4) + +/* maximum number of elements to sweep in each single step */ +#define GCSWEEPMAX (cast_int((GCSTEPSIZE / GCSWEEPCOST) / 4)) + +/* cost of calling one finalizer */ +#define GCFINALIZECOST GCSWEEPCOST + + +/* +** macro to adjust 'stepmul': 'stepmul' is actually used like +** 'stepmul / STEPMULADJ' (value chosen by tests) +*/ +#define STEPMULADJ 200 + + +/* +** macro to adjust 'pause': 'pause' is actually used like +** 'pause / PAUSEADJ' (value chosen by tests) +*/ +#define PAUSEADJ 100 + + +/* +** 'makewhite' erases all color bits then sets only the current white +** bit +*/ +#define maskcolors (~(bitmask(BLACKBIT) | WHITEBITS)) +#define makewhite(g,x) \ + (x->marked = cast_byte((x->marked & maskcolors) | luaC_white(g))) + +#define white2gray(x) resetbits(x->marked, WHITEBITS) +#define black2gray(x) resetbit(x->marked, BLACKBIT) + + +#define valiswhite(x) (iscollectable(x) && iswhite(gcvalue(x))) + +#define checkdeadkey(n) lua_assert(!ttisdeadkey(gkey(n)) || ttisnil(gval(n))) + + +#define checkconsistency(obj) \ + lua_longassert(!iscollectable(obj) || righttt(obj)) + + +#define markvalue(g,o) { checkconsistency(o); \ + if (valiswhite(o)) reallymarkobject(g,gcvalue(o)); } + +#define markobject(g,t) { if (iswhite(t)) reallymarkobject(g, obj2gco(t)); } + +/* +** mark an object that can be NULL (either because it is really optional, +** or it was stripped as debug info, or inside an uncompleted structure) +*/ +#define markobjectN(g,t) { if (t) markobject(g,t); } + +static void reallymarkobject (global_State *g, GCObject *o); + + +/* +** {====================================================== +** Generic functions +** ======================================================= +*/ + + +/* +** one after last element in a hash array +*/ +#define gnodelast(h) gnode(h, cast(size_t, sizenode(h))) + + +/* +** link collectable object 'o' into list pointed by 'p' +*/ +#define linkgclist(o,p) ((o)->gclist = (p), (p) = obj2gco(o)) + + +/* +** If key is not marked, mark its entry as dead. This allows key to be +** collected, but keeps its entry in the table. A dead node is needed +** when Lua looks up for a key (it may be part of a chain) and when +** traversing a weak table (key might be removed from the table during +** traversal). Other places never manipulate dead keys, because its +** associated nil value is enough to signal that the entry is logically +** empty. +*/ +static void removeentry (Node *n) { + lua_assert(ttisnil(gval(n))); + if (valiswhite(gkey(n))) + setdeadvalue(wgkey(n)); /* unused and unmarked key; remove it */ +} + + +/* +** tells whether a key or value can be cleared from a weak +** table. Non-collectable objects are never removed from weak +** tables. Strings behave as 'values', so are never removed too. for +** other objects: if really collected, cannot keep them; for objects +** being finalized, keep them in keys, but not in values +*/ +static int iscleared (global_State *g, const TValue *o) { + if (!iscollectable(o)) return 0; + else if (ttisstring(o)) { + markobject(g, tsvalue(o)); /* strings are 'values', so are never weak */ + return 0; + } + else return iswhite(gcvalue(o)); +} + + +/* +** barrier that moves collector forward, that is, mark the white object +** being pointed by a black object. (If in sweep phase, clear the black +** object to white [sweep it] to avoid other barrier calls for this +** same object.) +*/ +void luaC_barrier_ (lua_State *L, GCObject *o, GCObject *v) { + global_State *g = G(L); + lua_assert(isblack(o) && iswhite(v) && !isdead(g, v) && !isdead(g, o)); + if (keepinvariant(g)) /* must keep invariant? */ + reallymarkobject(g, v); /* restore invariant */ + else { /* sweep phase */ + lua_assert(issweepphase(g)); + makewhite(g, o); /* mark main obj. as white to avoid other barriers */ + } +} + + +/* +** barrier that moves collector backward, that is, mark the black object +** pointing to a white object as gray again. +*/ +void luaC_barrierback_ (lua_State *L, Table *t) { + global_State *g = G(L); + lua_assert(isblack(t) && !isdead(g, t)); + black2gray(t); /* make table gray (again) */ + linkgclist(t, g->grayagain); +} + + +/* +** barrier for assignments to closed upvalues. Because upvalues are +** shared among closures, it is impossible to know the color of all +** closures pointing to it. So, we assume that the object being assigned +** must be marked. +*/ +void luaC_upvalbarrier_ (lua_State *L, UpVal *uv) { + global_State *g = G(L); + GCObject *o = gcvalue(uv->v); + lua_assert(!upisopen(uv)); /* ensured by macro luaC_upvalbarrier */ + if (keepinvariant(g)) + markobject(g, o); +} + + +void luaC_fix (lua_State *L, GCObject *o) { + global_State *g = G(L); + lua_assert(g->allgc == o); /* object must be 1st in 'allgc' list! */ + white2gray(o); /* they will be gray forever */ + g->allgc = o->next; /* remove object from 'allgc' list */ + o->next = g->fixedgc; /* link it to 'fixedgc' list */ + g->fixedgc = o; +} + + +/* +** create a new collectable object (with given type and size) and link +** it to 'allgc' list. +*/ +GCObject *luaC_newobj (lua_State *L, int tt, size_t sz) { + global_State *g = G(L); + GCObject *o = cast(GCObject *, luaM_newobject(L, novariant(tt), sz)); + o->marked = luaC_white(g); + o->tt = tt; + o->next = g->allgc; + g->allgc = o; + return o; +} + +/* }====================================================== */ + + + +/* +** {====================================================== +** Mark functions +** ======================================================= +*/ + + +/* +** mark an object. Userdata, strings, and closed upvalues are visited +** and turned black here. Other objects are marked gray and added +** to appropriate list to be visited (and turned black) later. (Open +** upvalues are already linked in 'headuv' list.) +*/ +static void reallymarkobject (global_State *g, GCObject *o) { + reentry: + white2gray(o); + switch (o->tt) { + case LUA_TSHRSTR: { + gray2black(o); + g->GCmemtrav += sizelstring(gco2ts(o)->shrlen); + break; + } + case LUA_TLNGSTR: { + gray2black(o); + g->GCmemtrav += sizelstring(gco2ts(o)->u.lnglen); + break; + } + case LUA_TUSERDATA: { + TValue uvalue; + markobjectN(g, gco2u(o)->metatable); /* mark its metatable */ + gray2black(o); + g->GCmemtrav += sizeudata(gco2u(o)); + getuservalue(g->mainthread, gco2u(o), &uvalue); + if (valiswhite(&uvalue)) { /* markvalue(g, &uvalue); */ + o = gcvalue(&uvalue); + goto reentry; + } + break; + } + case LUA_TLCL: { + linkgclist(gco2lcl(o), g->gray); + break; + } + case LUA_TCCL: { + linkgclist(gco2ccl(o), g->gray); + break; + } + case LUA_TTABLE: { + linkgclist(gco2t(o), g->gray); + break; + } + case LUA_TTHREAD: { + linkgclist(gco2th(o), g->gray); + break; + } + case LUA_TPROTO: { + linkgclist(gco2p(o), g->gray); + break; + } + default: lua_assert(0); break; + } +} + + +/* +** mark metamethods for basic types +*/ +static void markmt (global_State *g) { + int i; + for (i=0; i < LUA_NUMTAGS; i++) + markobjectN(g, g->mt[i]); +} + + +/* +** mark all objects in list of being-finalized +*/ +static void markbeingfnz (global_State *g) { + GCObject *o; + for (o = g->tobefnz; o != NULL; o = o->next) + markobject(g, o); +} + + +/* +** Mark all values stored in marked open upvalues from non-marked threads. +** (Values from marked threads were already marked when traversing the +** thread.) Remove from the list threads that no longer have upvalues and +** not-marked threads. +*/ +static void remarkupvals (global_State *g) { + lua_State *thread; + lua_State **p = &g->twups; + while ((thread = *p) != NULL) { + lua_assert(!isblack(thread)); /* threads are never black */ + if (isgray(thread) && thread->openupval != NULL) + p = &thread->twups; /* keep marked thread with upvalues in the list */ + else { /* thread is not marked or without upvalues */ + UpVal *uv; + *p = thread->twups; /* remove thread from the list */ + thread->twups = thread; /* mark that it is out of list */ + for (uv = thread->openupval; uv != NULL; uv = uv->u.open.next) { + if (uv->u.open.touched) { + markvalue(g, uv->v); /* remark upvalue's value */ + uv->u.open.touched = 0; + } + } + } + } +} + + +/* +** mark root set and reset all gray lists, to start a new collection +*/ +static void restartcollection (global_State *g) { + g->gray = g->grayagain = NULL; + g->weak = g->allweak = g->ephemeron = NULL; + markobject(g, g->mainthread); + markvalue(g, &g->l_registry); + markmt(g); + markbeingfnz(g); /* mark any finalizing object left from previous cycle */ +} + +/* }====================================================== */ + + +/* +** {====================================================== +** Traverse functions +** ======================================================= +*/ + +/* +** Traverse a table with weak values and link it to proper list. During +** propagate phase, keep it in 'grayagain' list, to be revisited in the +** atomic phase. In the atomic phase, if table has any white value, +** put it in 'weak' list, to be cleared. +*/ +static void traverseweakvalue (global_State *g, Table *h) { + Node *n, *limit = gnodelast(h); + /* if there is array part, assume it may have white values (it is not + worth traversing it now just to check) */ + int hasclears = (h->sizearray > 0); + for (n = gnode(h, 0); n < limit; n++) { /* traverse hash part */ + checkdeadkey(n); + if (ttisnil(gval(n))) /* entry is empty? */ + removeentry(n); /* remove it */ + else { + lua_assert(!ttisnil(gkey(n))); + markvalue(g, gkey(n)); /* mark key */ + if (!hasclears && iscleared(g, gval(n))) /* is there a white value? */ + hasclears = 1; /* table will have to be cleared */ + } + } + if (g->gcstate == GCSpropagate) + linkgclist(h, g->grayagain); /* must retraverse it in atomic phase */ + else if (hasclears) + linkgclist(h, g->weak); /* has to be cleared later */ +} + + +/* +** Traverse an ephemeron table and link it to proper list. Returns true +** iff any object was marked during this traversal (which implies that +** convergence has to continue). During propagation phase, keep table +** in 'grayagain' list, to be visited again in the atomic phase. In +** the atomic phase, if table has any white->white entry, it has to +** be revisited during ephemeron convergence (as that key may turn +** black). Otherwise, if it has any white key, table has to be cleared +** (in the atomic phase). +*/ +static int traverseephemeron (global_State *g, Table *h) { + int marked = 0; /* true if an object is marked in this traversal */ + int hasclears = 0; /* true if table has white keys */ + int hasww = 0; /* true if table has entry "white-key -> white-value" */ + Node *n, *limit = gnodelast(h); + unsigned int i; + /* traverse array part */ + for (i = 0; i < h->sizearray; i++) { + if (valiswhite(&h->array[i])) { + marked = 1; + reallymarkobject(g, gcvalue(&h->array[i])); + } + } + /* traverse hash part */ + for (n = gnode(h, 0); n < limit; n++) { + checkdeadkey(n); + if (ttisnil(gval(n))) /* entry is empty? */ + removeentry(n); /* remove it */ + else if (iscleared(g, gkey(n))) { /* key is not marked (yet)? */ + hasclears = 1; /* table must be cleared */ + if (valiswhite(gval(n))) /* value not marked yet? */ + hasww = 1; /* white-white entry */ + } + else if (valiswhite(gval(n))) { /* value not marked yet? */ + marked = 1; + reallymarkobject(g, gcvalue(gval(n))); /* mark it now */ + } + } + /* link table into proper list */ + if (g->gcstate == GCSpropagate) + linkgclist(h, g->grayagain); /* must retraverse it in atomic phase */ + else if (hasww) /* table has white->white entries? */ + linkgclist(h, g->ephemeron); /* have to propagate again */ + else if (hasclears) /* table has white keys? */ + linkgclist(h, g->allweak); /* may have to clean white keys */ + return marked; +} + + +static void traversestrongtable (global_State *g, Table *h) { + Node *n, *limit = gnodelast(h); + unsigned int i; + for (i = 0; i < h->sizearray; i++) /* traverse array part */ + markvalue(g, &h->array[i]); + for (n = gnode(h, 0); n < limit; n++) { /* traverse hash part */ + checkdeadkey(n); + if (ttisnil(gval(n))) /* entry is empty? */ + removeentry(n); /* remove it */ + else { + lua_assert(!ttisnil(gkey(n))); + markvalue(g, gkey(n)); /* mark key */ + markvalue(g, gval(n)); /* mark value */ + } + } +} + + +static lu_mem traversetable (global_State *g, Table *h) { + const char *weakkey, *weakvalue; + const TValue *mode = gfasttm(g, h->metatable, TM_MODE); + markobjectN(g, h->metatable); + if (mode && ttisstring(mode) && /* is there a weak mode? */ + ((weakkey = strchr(svalue(mode), 'k')), + (weakvalue = strchr(svalue(mode), 'v')), + (weakkey || weakvalue))) { /* is really weak? */ + black2gray(h); /* keep table gray */ + if (!weakkey) /* strong keys? */ + traverseweakvalue(g, h); + else if (!weakvalue) /* strong values? */ + traverseephemeron(g, h); + else /* all weak */ + linkgclist(h, g->allweak); /* nothing to traverse now */ + } + else /* not weak */ + traversestrongtable(g, h); + return sizeof(Table) + sizeof(TValue) * h->sizearray + + sizeof(Node) * cast(size_t, allocsizenode(h)); +} + + +/* +** Traverse a prototype. (While a prototype is being build, its +** arrays can be larger than needed; the extra slots are filled with +** NULL, so the use of 'markobjectN') +*/ +static int traverseproto (global_State *g, Proto *f) { + int i; + if (f->cache && iswhite(f->cache)) + f->cache = NULL; /* allow cache to be collected */ + markobjectN(g, f->source); + for (i = 0; i < f->sizek; i++) /* mark literals */ + markvalue(g, &f->k[i]); + for (i = 0; i < f->sizeupvalues; i++) /* mark upvalue names */ + markobjectN(g, f->upvalues[i].name); + for (i = 0; i < f->sizep; i++) /* mark nested protos */ + markobjectN(g, f->p[i]); + for (i = 0; i < f->sizelocvars; i++) /* mark local-variable names */ + markobjectN(g, f->locvars[i].varname); + return sizeof(Proto) + sizeof(Instruction) * f->sizecode + + sizeof(Proto *) * f->sizep + + sizeof(TValue) * f->sizek + + sizeof(int) * f->sizelineinfo + + sizeof(LocVar) * f->sizelocvars + + sizeof(Upvaldesc) * f->sizeupvalues; +} + + +static lu_mem traverseCclosure (global_State *g, CClosure *cl) { + int i; + for (i = 0; i < cl->nupvalues; i++) /* mark its upvalues */ + markvalue(g, &cl->upvalue[i]); + return sizeCclosure(cl->nupvalues); +} + +/* +** open upvalues point to values in a thread, so those values should +** be marked when the thread is traversed except in the atomic phase +** (because then the value cannot be changed by the thread and the +** thread may not be traversed again) +*/ +static lu_mem traverseLclosure (global_State *g, LClosure *cl) { + int i; + markobjectN(g, cl->p); /* mark its prototype */ + for (i = 0; i < cl->nupvalues; i++) { /* mark its upvalues */ + UpVal *uv = cl->upvals[i]; + if (uv != NULL) { + if (upisopen(uv) && g->gcstate != GCSinsideatomic) + uv->u.open.touched = 1; /* can be marked in 'remarkupvals' */ + else + markvalue(g, uv->v); + } + } + return sizeLclosure(cl->nupvalues); +} + + +static lu_mem traversethread (global_State *g, lua_State *th) { + StkId o = th->stack; + if (o == NULL) + return 1; /* stack not completely built yet */ + lua_assert(g->gcstate == GCSinsideatomic || + th->openupval == NULL || isintwups(th)); + for (; o < th->top; o++) /* mark live elements in the stack */ + markvalue(g, o); + if (g->gcstate == GCSinsideatomic) { /* final traversal? */ + StkId lim = th->stack + th->stacksize; /* real end of stack */ + for (; o < lim; o++) /* clear not-marked stack slice */ + setnilvalue(o); + /* 'remarkupvals' may have removed thread from 'twups' list */ + if (!isintwups(th) && th->openupval != NULL) { + th->twups = g->twups; /* link it back to the list */ + g->twups = th; + } + } + else if (g->gckind != KGC_EMERGENCY) + luaD_shrinkstack(th); /* do not change stack in emergency cycle */ + return (sizeof(lua_State) + sizeof(TValue) * th->stacksize + + sizeof(CallInfo) * th->nci); +} + + +/* +** traverse one gray object, turning it to black (except for threads, +** which are always gray). +*/ +static void propagatemark (global_State *g) { + lu_mem size; + GCObject *o = g->gray; + lua_assert(isgray(o)); + gray2black(o); + switch (o->tt) { + case LUA_TTABLE: { + Table *h = gco2t(o); + g->gray = h->gclist; /* remove from 'gray' list */ + size = traversetable(g, h); + break; + } + case LUA_TLCL: { + LClosure *cl = gco2lcl(o); + g->gray = cl->gclist; /* remove from 'gray' list */ + size = traverseLclosure(g, cl); + break; + } + case LUA_TCCL: { + CClosure *cl = gco2ccl(o); + g->gray = cl->gclist; /* remove from 'gray' list */ + size = traverseCclosure(g, cl); + break; + } + case LUA_TTHREAD: { + lua_State *th = gco2th(o); + g->gray = th->gclist; /* remove from 'gray' list */ + linkgclist(th, g->grayagain); /* insert into 'grayagain' list */ + black2gray(o); + size = traversethread(g, th); + break; + } + case LUA_TPROTO: { + Proto *p = gco2p(o); + g->gray = p->gclist; /* remove from 'gray' list */ + size = traverseproto(g, p); + break; + } + default: lua_assert(0); return; + } + g->GCmemtrav += size; +} + + +static void propagateall (global_State *g) { + while (g->gray) propagatemark(g); +} + + +static void convergeephemerons (global_State *g) { + int changed; + do { + GCObject *w; + GCObject *next = g->ephemeron; /* get ephemeron list */ + g->ephemeron = NULL; /* tables may return to this list when traversed */ + changed = 0; + while ((w = next) != NULL) { + next = gco2t(w)->gclist; + if (traverseephemeron(g, gco2t(w))) { /* traverse marked some value? */ + propagateall(g); /* propagate changes */ + changed = 1; /* will have to revisit all ephemeron tables */ + } + } + } while (changed); +} + +/* }====================================================== */ + + +/* +** {====================================================== +** Sweep Functions +** ======================================================= +*/ + + +/* +** clear entries with unmarked keys from all weaktables in list 'l' up +** to element 'f' +*/ +static void clearkeys (global_State *g, GCObject *l, GCObject *f) { + for (; l != f; l = gco2t(l)->gclist) { + Table *h = gco2t(l); + Node *n, *limit = gnodelast(h); + for (n = gnode(h, 0); n < limit; n++) { + if (!ttisnil(gval(n)) && (iscleared(g, gkey(n)))) { + setnilvalue(gval(n)); /* remove value ... */ + removeentry(n); /* and remove entry from table */ + } + } + } +} + + +/* +** clear entries with unmarked values from all weaktables in list 'l' up +** to element 'f' +*/ +static void clearvalues (global_State *g, GCObject *l, GCObject *f) { + for (; l != f; l = gco2t(l)->gclist) { + Table *h = gco2t(l); + Node *n, *limit = gnodelast(h); + unsigned int i; + for (i = 0; i < h->sizearray; i++) { + TValue *o = &h->array[i]; + if (iscleared(g, o)) /* value was collected? */ + setnilvalue(o); /* remove value */ + } + for (n = gnode(h, 0); n < limit; n++) { + if (!ttisnil(gval(n)) && iscleared(g, gval(n))) { + setnilvalue(gval(n)); /* remove value ... */ + removeentry(n); /* and remove entry from table */ + } + } + } +} + + +void luaC_upvdeccount (lua_State *L, UpVal *uv) { + lua_assert(uv->refcount > 0); + uv->refcount--; + if (uv->refcount == 0 && !upisopen(uv)) + luaM_free(L, uv); +} + + +static void freeLclosure (lua_State *L, LClosure *cl) { + int i; + for (i = 0; i < cl->nupvalues; i++) { + UpVal *uv = cl->upvals[i]; + if (uv) + luaC_upvdeccount(L, uv); + } + luaM_freemem(L, cl, sizeLclosure(cl->nupvalues)); +} + + +static void freeobj (lua_State *L, GCObject *o) { + switch (o->tt) { + case LUA_TPROTO: luaF_freeproto(L, gco2p(o)); break; + case LUA_TLCL: { + freeLclosure(L, gco2lcl(o)); + break; + } + case LUA_TCCL: { + luaM_freemem(L, o, sizeCclosure(gco2ccl(o)->nupvalues)); + break; + } + case LUA_TTABLE: luaH_free(L, gco2t(o)); break; + case LUA_TTHREAD: luaE_freethread(L, gco2th(o)); break; + case LUA_TUSERDATA: luaM_freemem(L, o, sizeudata(gco2u(o))); break; + case LUA_TSHRSTR: + luaS_remove(L, gco2ts(o)); /* remove it from hash table */ + luaM_freemem(L, o, sizelstring(gco2ts(o)->shrlen)); + break; + case LUA_TLNGSTR: { + luaM_freemem(L, o, sizelstring(gco2ts(o)->u.lnglen)); + break; + } + default: lua_assert(0); + } +} + + +#define sweepwholelist(L,p) sweeplist(L,p,MAX_LUMEM) +static GCObject **sweeplist (lua_State *L, GCObject **p, lu_mem count); + + +/* +** sweep at most 'count' elements from a list of GCObjects erasing dead +** objects, where a dead object is one marked with the old (non current) +** white; change all non-dead objects back to white, preparing for next +** collection cycle. Return where to continue the traversal or NULL if +** list is finished. +*/ +static GCObject **sweeplist (lua_State *L, GCObject **p, lu_mem count) { + global_State *g = G(L); + int ow = otherwhite(g); + int white = luaC_white(g); /* current white */ + while (*p != NULL && count-- > 0) { + GCObject *curr = *p; + int marked = curr->marked; + if (isdeadm(ow, marked)) { /* is 'curr' dead? */ + *p = curr->next; /* remove 'curr' from list */ + freeobj(L, curr); /* erase 'curr' */ + } + else { /* change mark to 'white' */ + curr->marked = cast_byte((marked & maskcolors) | white); + p = &curr->next; /* go to next element */ + } + } + return (*p == NULL) ? NULL : p; +} + + +/* +** sweep a list until a live object (or end of list) +*/ +static GCObject **sweeptolive (lua_State *L, GCObject **p) { + GCObject **old = p; + do { + p = sweeplist(L, p, 1); + } while (p == old); + return p; +} + +/* }====================================================== */ + + +/* +** {====================================================== +** Finalization +** ======================================================= +*/ + +/* +** If possible, shrink string table +*/ +static void checkSizes (lua_State *L, global_State *g) { + if (g->gckind != KGC_EMERGENCY) { + l_mem olddebt = g->GCdebt; + if (g->strt.nuse < g->strt.size / 4) /* string table too big? */ + luaS_resize(L, g->strt.size / 2); /* shrink it a little */ + g->GCestimate += g->GCdebt - olddebt; /* update estimate */ + } +} + + +static GCObject *udata2finalize (global_State *g) { + GCObject *o = g->tobefnz; /* get first element */ + lua_assert(tofinalize(o)); + g->tobefnz = o->next; /* remove it from 'tobefnz' list */ + o->next = g->allgc; /* return it to 'allgc' list */ + g->allgc = o; + resetbit(o->marked, FINALIZEDBIT); /* object is "normal" again */ + if (issweepphase(g)) + makewhite(g, o); /* "sweep" object */ + return o; +} + + +static void dothecall (lua_State *L, void *ud) { + UNUSED(ud); + luaD_callnoyield(L, L->top - 2, 0); +} + + +static void GCTM (lua_State *L, int propagateerrors) { + global_State *g = G(L); + const TValue *tm; + TValue v; + setgcovalue(L, &v, udata2finalize(g)); + tm = luaT_gettmbyobj(L, &v, TM_GC); + if (tm != NULL && ttisfunction(tm)) { /* is there a finalizer? */ + int status; + lu_byte oldah = L->allowhook; + int running = g->gcrunning; + L->allowhook = 0; /* stop debug hooks during GC metamethod */ + g->gcrunning = 0; /* avoid GC steps */ + setobj2s(L, L->top, tm); /* push finalizer... */ + setobj2s(L, L->top + 1, &v); /* ... and its argument */ + L->top += 2; /* and (next line) call the finalizer */ + L->ci->callstatus |= CIST_FIN; /* will run a finalizer */ + status = luaD_pcall(L, dothecall, NULL, savestack(L, L->top - 2), 0); + L->ci->callstatus &= ~CIST_FIN; /* not running a finalizer anymore */ + L->allowhook = oldah; /* restore hooks */ + g->gcrunning = running; /* restore state */ + if (status != LUA_OK && propagateerrors) { /* error while running __gc? */ + if (status == LUA_ERRRUN) { /* is there an error object? */ + const char *msg = (ttisstring(L->top - 1)) + ? svalue(L->top - 1) + : "no message"; + luaO_pushfstring(L, "error in __gc metamethod (%s)", msg); + status = LUA_ERRGCMM; /* error in __gc metamethod */ + } + luaD_throw(L, status); /* re-throw error */ + } + } +} + + +/* +** call a few (up to 'g->gcfinnum') finalizers +*/ +static int runafewfinalizers (lua_State *L) { + global_State *g = G(L); + unsigned int i; + lua_assert(!g->tobefnz || g->gcfinnum > 0); + for (i = 0; g->tobefnz && i < g->gcfinnum; i++) + GCTM(L, 1); /* call one finalizer */ + g->gcfinnum = (!g->tobefnz) ? 0 /* nothing more to finalize? */ + : g->gcfinnum * 2; /* else call a few more next time */ + return i; +} + + +/* +** call all pending finalizers +*/ +static void callallpendingfinalizers (lua_State *L) { + global_State *g = G(L); + while (g->tobefnz) + GCTM(L, 0); +} + + +/* +** find last 'next' field in list 'p' list (to add elements in its end) +*/ +static GCObject **findlast (GCObject **p) { + while (*p != NULL) + p = &(*p)->next; + return p; +} + + +/* +** move all unreachable objects (or 'all' objects) that need +** finalization from list 'finobj' to list 'tobefnz' (to be finalized) +*/ +static void separatetobefnz (global_State *g, int all) { + GCObject *curr; + GCObject **p = &g->finobj; + GCObject **lastnext = findlast(&g->tobefnz); + while ((curr = *p) != NULL) { /* traverse all finalizable objects */ + lua_assert(tofinalize(curr)); + if (!(iswhite(curr) || all)) /* not being collected? */ + p = &curr->next; /* don't bother with it */ + else { + *p = curr->next; /* remove 'curr' from 'finobj' list */ + curr->next = *lastnext; /* link at the end of 'tobefnz' list */ + *lastnext = curr; + lastnext = &curr->next; + } + } +} + + +/* +** if object 'o' has a finalizer, remove it from 'allgc' list (must +** search the list to find it) and link it in 'finobj' list. +*/ +void luaC_checkfinalizer (lua_State *L, GCObject *o, Table *mt) { + global_State *g = G(L); + if (tofinalize(o) || /* obj. is already marked... */ + gfasttm(g, mt, TM_GC) == NULL) /* or has no finalizer? */ + return; /* nothing to be done */ + else { /* move 'o' to 'finobj' list */ + GCObject **p; + if (issweepphase(g)) { + makewhite(g, o); /* "sweep" object 'o' */ + if (g->sweepgc == &o->next) /* should not remove 'sweepgc' object */ + g->sweepgc = sweeptolive(L, g->sweepgc); /* change 'sweepgc' */ + } + /* search for pointer pointing to 'o' */ + for (p = &g->allgc; *p != o; p = &(*p)->next) { /* empty */ } + *p = o->next; /* remove 'o' from 'allgc' list */ + o->next = g->finobj; /* link it in 'finobj' list */ + g->finobj = o; + l_setbit(o->marked, FINALIZEDBIT); /* mark it as such */ + } +} + +/* }====================================================== */ + + + +/* +** {====================================================== +** GC control +** ======================================================= +*/ + + +/* +** Set a reasonable "time" to wait before starting a new GC cycle; cycle +** will start when memory use hits threshold. (Division by 'estimate' +** should be OK: it cannot be zero (because Lua cannot even start with +** less than PAUSEADJ bytes). +*/ +static void setpause (global_State *g) { + l_mem threshold, debt; + l_mem estimate = g->GCestimate / PAUSEADJ; /* adjust 'estimate' */ + lua_assert(estimate > 0); + threshold = (g->gcpause < MAX_LMEM / estimate) /* overflow? */ + ? estimate * g->gcpause /* no overflow */ + : MAX_LMEM; /* overflow; truncate to maximum */ + debt = gettotalbytes(g) - threshold; + luaE_setdebt(g, debt); +} + + +/* +** Enter first sweep phase. +** The call to 'sweeplist' tries to make pointer point to an object +** inside the list (instead of to the header), so that the real sweep do +** not need to skip objects created between "now" and the start of the +** real sweep. +*/ +static void entersweep (lua_State *L) { + global_State *g = G(L); + g->gcstate = GCSswpallgc; + lua_assert(g->sweepgc == NULL); + g->sweepgc = sweeplist(L, &g->allgc, 1); +} + + +void luaC_freeallobjects (lua_State *L) { + global_State *g = G(L); + separatetobefnz(g, 1); /* separate all objects with finalizers */ + lua_assert(g->finobj == NULL); + callallpendingfinalizers(L); + lua_assert(g->tobefnz == NULL); + g->currentwhite = WHITEBITS; /* this "white" makes all objects look dead */ + g->gckind = KGC_NORMAL; + sweepwholelist(L, &g->finobj); + sweepwholelist(L, &g->allgc); + sweepwholelist(L, &g->fixedgc); /* collect fixed objects */ + lua_assert(g->strt.nuse == 0); +} + + +static l_mem atomic (lua_State *L) { + global_State *g = G(L); + l_mem work; + GCObject *origweak, *origall; + GCObject *grayagain = g->grayagain; /* save original list */ + lua_assert(g->ephemeron == NULL && g->weak == NULL); + lua_assert(!iswhite(g->mainthread)); + g->gcstate = GCSinsideatomic; + g->GCmemtrav = 0; /* start counting work */ + markobject(g, L); /* mark running thread */ + /* registry and global metatables may be changed by API */ + markvalue(g, &g->l_registry); + markmt(g); /* mark global metatables */ + /* remark occasional upvalues of (maybe) dead threads */ + remarkupvals(g); + propagateall(g); /* propagate changes */ + work = g->GCmemtrav; /* stop counting (do not recount 'grayagain') */ + g->gray = grayagain; + propagateall(g); /* traverse 'grayagain' list */ + g->GCmemtrav = 0; /* restart counting */ + convergeephemerons(g); + /* at this point, all strongly accessible objects are marked. */ + /* Clear values from weak tables, before checking finalizers */ + clearvalues(g, g->weak, NULL); + clearvalues(g, g->allweak, NULL); + origweak = g->weak; origall = g->allweak; + work += g->GCmemtrav; /* stop counting (objects being finalized) */ + separatetobefnz(g, 0); /* separate objects to be finalized */ + g->gcfinnum = 1; /* there may be objects to be finalized */ + markbeingfnz(g); /* mark objects that will be finalized */ + propagateall(g); /* remark, to propagate 'resurrection' */ + g->GCmemtrav = 0; /* restart counting */ + convergeephemerons(g); + /* at this point, all resurrected objects are marked. */ + /* remove dead objects from weak tables */ + clearkeys(g, g->ephemeron, NULL); /* clear keys from all ephemeron tables */ + clearkeys(g, g->allweak, NULL); /* clear keys from all 'allweak' tables */ + /* clear values from resurrected weak tables */ + clearvalues(g, g->weak, origweak); + clearvalues(g, g->allweak, origall); + luaS_clearcache(g); + g->currentwhite = cast_byte(otherwhite(g)); /* flip current white */ + work += g->GCmemtrav; /* complete counting */ + return work; /* estimate of memory marked by 'atomic' */ +} + + +static lu_mem sweepstep (lua_State *L, global_State *g, + int nextstate, GCObject **nextlist) { + if (g->sweepgc) { + l_mem olddebt = g->GCdebt; + g->sweepgc = sweeplist(L, g->sweepgc, GCSWEEPMAX); + g->GCestimate += g->GCdebt - olddebt; /* update estimate */ + if (g->sweepgc) /* is there still something to sweep? */ + return (GCSWEEPMAX * GCSWEEPCOST); + } + /* else enter next state */ + g->gcstate = nextstate; + g->sweepgc = nextlist; + return 0; +} + + +static lu_mem singlestep (lua_State *L) { + global_State *g = G(L); + switch (g->gcstate) { + case GCSpause: { + g->GCmemtrav = g->strt.size * sizeof(GCObject*); + restartcollection(g); + g->gcstate = GCSpropagate; + return g->GCmemtrav; + } + case GCSpropagate: { + g->GCmemtrav = 0; + lua_assert(g->gray); + propagatemark(g); + if (g->gray == NULL) /* no more gray objects? */ + g->gcstate = GCSatomic; /* finish propagate phase */ + return g->GCmemtrav; /* memory traversed in this step */ + } + case GCSatomic: { + lu_mem work; + propagateall(g); /* make sure gray list is empty */ + work = atomic(L); /* work is what was traversed by 'atomic' */ + entersweep(L); + g->GCestimate = gettotalbytes(g); /* first estimate */; + return work; + } + case GCSswpallgc: { /* sweep "regular" objects */ + return sweepstep(L, g, GCSswpfinobj, &g->finobj); + } + case GCSswpfinobj: { /* sweep objects with finalizers */ + return sweepstep(L, g, GCSswptobefnz, &g->tobefnz); + } + case GCSswptobefnz: { /* sweep objects to be finalized */ + return sweepstep(L, g, GCSswpend, NULL); + } + case GCSswpend: { /* finish sweeps */ + makewhite(g, g->mainthread); /* sweep main thread */ + checkSizes(L, g); + g->gcstate = GCScallfin; + return 0; + } + case GCScallfin: { /* call remaining finalizers */ + if (g->tobefnz && g->gckind != KGC_EMERGENCY) { + int n = runafewfinalizers(L); + return (n * GCFINALIZECOST); + } + else { /* emergency mode or no more finalizers */ + g->gcstate = GCSpause; /* finish collection */ + return 0; + } + } + default: lua_assert(0); return 0; + } +} + + +/* +** advances the garbage collector until it reaches a state allowed +** by 'statemask' +*/ +void luaC_runtilstate (lua_State *L, int statesmask) { + global_State *g = G(L); + while (!testbit(statesmask, g->gcstate)) + singlestep(L); +} + + +/* +** get GC debt and convert it from Kb to 'work units' (avoid zero debt +** and overflows) +*/ +static l_mem getdebt (global_State *g) { + l_mem debt = g->GCdebt; + int stepmul = g->gcstepmul; + if (debt <= 0) return 0; /* minimal debt */ + else { + debt = (debt / STEPMULADJ) + 1; + debt = (debt < MAX_LMEM / stepmul) ? debt * stepmul : MAX_LMEM; + return debt; + } +} + +/* +** performs a basic GC step when collector is running +*/ +void luaC_step (lua_State *L) { + global_State *g = G(L); + l_mem debt = getdebt(g); /* GC deficit (be paid now) */ + if (!g->gcrunning) { /* not running? */ + luaE_setdebt(g, -GCSTEPSIZE * 10); /* avoid being called too often */ + return; + } + do { /* repeat until pause or enough "credit" (negative debt) */ + lu_mem work = singlestep(L); /* perform one single step */ + debt -= work; + } while (debt > -GCSTEPSIZE && g->gcstate != GCSpause); + if (g->gcstate == GCSpause) + setpause(g); /* pause until next cycle */ + else { + debt = (debt / g->gcstepmul) * STEPMULADJ; /* convert 'work units' to Kb */ + luaE_setdebt(g, debt); + runafewfinalizers(L); + } +} + + +/* +** Performs a full GC cycle; if 'isemergency', set a flag to avoid +** some operations which could change the interpreter state in some +** unexpected ways (running finalizers and shrinking some structures). +** Before running the collection, check 'keepinvariant'; if it is true, +** there may be some objects marked as black, so the collector has +** to sweep all objects to turn them back to white (as white has not +** changed, nothing will be collected). +*/ +void luaC_fullgc (lua_State *L, int isemergency) { + global_State *g = G(L); + lua_assert(g->gckind == KGC_NORMAL); + if (isemergency) g->gckind = KGC_EMERGENCY; /* set flag */ + if (keepinvariant(g)) { /* black objects? */ + entersweep(L); /* sweep everything to turn them back to white */ + } + /* finish any pending sweep phase to start a new cycle */ + luaC_runtilstate(L, bitmask(GCSpause)); + luaC_runtilstate(L, ~bitmask(GCSpause)); /* start new collection */ + luaC_runtilstate(L, bitmask(GCScallfin)); /* run up to finalizers */ + /* estimate must be correct after a full GC cycle */ + lua_assert(g->GCestimate == gettotalbytes(g)); + luaC_runtilstate(L, bitmask(GCSpause)); /* finish collection */ + g->gckind = KGC_NORMAL; + setpause(g); +} + +/* }====================================================== */ + + |