1 /* 2 ** $Id: lgc.h,v 2.91 2015/12/21 13:02:14 roberto Exp $ 3 ** Garbage Collector 4 ** See Copyright Notice in lua.h 5 */ 6 7 #ifndef lgc_h 8 #define lgc_h 9 10 11 #include "lobject.h" 12 #include "lstate.h" 13 14 /* 15 ** Collectable objects may have one of three colors: white, which 16 ** means the object is not marked; gray, which means the 17 ** object is marked, but its references may be not marked; and 18 ** black, which means that the object and all its references are marked. 19 ** The main invariant of the garbage collector, while marking objects, 20 ** is that a black object can never point to a white one. Moreover, 21 ** any gray object must be in a "gray list" (gray, grayagain, weak, 22 ** allweak, ephemeron) so that it can be visited again before finishing 23 ** the collection cycle. These lists have no meaning when the invariant 24 ** is not being enforced (e.g., sweep phase). 25 */ 26 27 28 29 /* how much to allocate before next GC step */ 30 #if !defined(GCSTEPSIZE) 31 /* ~100 small strings */ 32 #define GCSTEPSIZE (cast_int(100 * sizeof(TString))) 33 #endif 34 35 36 /* 37 ** Possible states of the Garbage Collector 38 */ 39 #define GCSpropagate 0 40 #define GCSatomic 1 41 #define GCSswpallgc 2 42 #define GCSswpfinobj 3 43 #define GCSswptobefnz 4 44 #define GCSswpend 5 45 #define GCScallfin 6 46 #define GCSpause 7 47 48 49 #define issweepphase(g) \ 50 (GCSswpallgc <= (g)->gcstate && (g)->gcstate <= GCSswpend) 51 52 53 /* 54 ** macro to tell when main invariant (white objects cannot point to black 55 ** ones) must be kept. During a collection, the sweep 56 ** phase may break the invariant, as objects turned white may point to 57 ** still-black objects. The invariant is restored when sweep ends and 58 ** all objects are white again. 59 */ 60 61 #define keepinvariant(g) ((g)->gcstate <= GCSatomic) 62 63 64 /* 65 ** some useful bit tricks 66 */ 67 #define resetbits(x,m) ((x) &= cast(lu_byte, ~(m))) 68 #define setbits(x,m) ((x) |= (m)) 69 #define testbits(x,m) ((x) & (m)) 70 #define bitmask(b) (1<<(b)) 71 #define bit2mask(b1,b2) (bitmask(b1) | bitmask(b2)) 72 #define l_setbit(x,b) setbits(x, bitmask(b)) 73 #define resetbit(x,b) resetbits(x, bitmask(b)) 74 #define testbit(x,b) testbits(x, bitmask(b)) 75 76 77 /* Layout for bit use in 'marked' field: */ 78 #define WHITE0BIT 0 /* object is white (type 0) */ 79 #define WHITE1BIT 1 /* object is white (type 1) */ 80 #define BLACKBIT 2 /* object is black */ 81 #define FINALIZEDBIT 3 /* object has been marked for finalization */ 82 /* bit 7 is currently used by tests (luaL_checkmemory) */ 83 84 #define WHITEBITS bit2mask(WHITE0BIT, WHITE1BIT) 85 86 87 #define iswhite(x) testbits((x)->marked, WHITEBITS) 88 #define isblack(x) testbit((x)->marked, BLACKBIT) 89 #define isgray(x) /* neither white nor black */ \ 90 (!testbits((x)->marked, WHITEBITS | bitmask(BLACKBIT))) 91 92 #define tofinalize(x) testbit((x)->marked, FINALIZEDBIT) 93 94 #define otherwhite(g) ((g)->currentwhite ^ WHITEBITS) 95 #define isdeadm(ow,m) (!(((m) ^ WHITEBITS) & (ow))) 96 #define isdead(g,v) isdeadm(otherwhite(g), (v)->marked) 97 98 #define changewhite(x) ((x)->marked ^= WHITEBITS) 99 #define gray2black(x) l_setbit((x)->marked, BLACKBIT) 100 101 #define luaC_white(g) cast(lu_byte, (g)->currentwhite & WHITEBITS) 102 103 104 /* 105 ** Does one step of collection when debt becomes positive. 'pre'/'pos' 106 ** allows some adjustments to be done only when needed. macro 107 ** 'condchangemem' is used only for heavy tests (forcing a full 108 ** GC cycle on every opportunity) 109 */ 110 #define luaC_condGC(L,pre,pos) \ 111 { if (G(L)->GCdebt > 0) { pre; luaC_step(L); pos;}; \ 112 condchangemem(L,pre,pos); } 113 114 /* more often than not, 'pre'/'pos' are empty */ 115 #define luaC_checkGC(L) luaC_condGC(L,(void)0,(void)0) 116 117 118 #define luaC_barrier(L,p,v) ( \ 119 (iscollectable(v) && isblack(p) && iswhite(gcvalue(v))) ? \ 120 luaC_barrier_(L,obj2gco(p),gcvalue(v)) : cast_void(0)) 121 122 #define luaC_barrierback(L,p,v) ( \ 123 (iscollectable(v) && isblack(p) && iswhite(gcvalue(v))) ? \ 124 luaC_barrierback_(L,p) : cast_void(0)) 125 126 #define luaC_objbarrier(L,p,o) ( \ 127 (isblack(p) && iswhite(o)) ? \ 128 luaC_barrier_(L,obj2gco(p),obj2gco(o)) : cast_void(0)) 129 130 #define luaC_upvalbarrier(L,uv) ( \ 131 (iscollectable((uv)->v) && !upisopen(uv)) ? \ 132 luaC_upvalbarrier_(L,uv) : cast_void(0)) 133 134 LUAI_FUNC void luaC_fix (lua_State *L, GCObject *o); 135 LUAI_FUNC void luaC_freeallobjects (lua_State *L); 136 LUAI_FUNC void luaC_step (lua_State *L); 137 LUAI_FUNC void luaC_runtilstate (lua_State *L, int statesmask); 138 LUAI_FUNC void luaC_fullgc (lua_State *L, int isemergency); 139 LUAI_FUNC GCObject *luaC_newobj (lua_State *L, int tt, size_t sz); 140 LUAI_FUNC void luaC_barrier_ (lua_State *L, GCObject *o, GCObject *v); 141 LUAI_FUNC void luaC_barrierback_ (lua_State *L, Table *o); 142 LUAI_FUNC void luaC_upvalbarrier_ (lua_State *L, UpVal *uv); 143 LUAI_FUNC void luaC_checkfinalizer (lua_State *L, GCObject *o, Table *mt); 144 LUAI_FUNC void luaC_upvdeccount (lua_State *L, UpVal *uv); 145 146 147 #endif 148