1 /* 2 ** $Id: lgc.h,v 2.58.1.1 2013/04/12 18:48:47 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 GCSsweepstring 2 42 #define GCSsweepudata 3 43 #define GCSsweep 4 44 #define GCSpause 5 45 46 47 #define issweepphase(g) \ 48 (GCSsweepstring <= (g)->gcstate && (g)->gcstate <= GCSsweep) 49 50 #define isgenerational(g) ((g)->gckind == KGC_GEN) 51 52 /* 53 ** macros to tell when main invariant (white objects cannot point to black 54 ** ones) must be kept. During a non-generational collection, the sweep 55 ** phase may break the invariant, as objects turned white may point to 56 ** still-black objects. The invariant is restored when sweep ends and 57 ** all objects are white again. During a generational collection, the 58 ** invariant must be kept all times. 59 */ 60 61 #define keepinvariant(g) (isgenerational(g) || g->gcstate <= GCSatomic) 62 63 64 /* 65 ** Outside the collector, the state in generational mode is kept in 66 ** 'propagate', so 'keepinvariant' is always true. 67 */ 68 #define keepinvariantout(g) \ 69 check_exp(g->gcstate == GCSpropagate || !isgenerational(g), \ 70 g->gcstate <= GCSatomic) 71 72 73 /* 74 ** some useful bit tricks 75 */ 76 #define resetbits(x,m) ((x) &= cast(lu_byte, ~(m))) 77 #define setbits(x,m) ((x) |= (m)) 78 #define testbits(x,m) ((x) & (m)) 79 #define bitmask(b) (1<<(b)) 80 #define bit2mask(b1,b2) (bitmask(b1) | bitmask(b2)) 81 #define l_setbit(x,b) setbits(x, bitmask(b)) 82 #define resetbit(x,b) resetbits(x, bitmask(b)) 83 #define testbit(x,b) testbits(x, bitmask(b)) 84 85 86 /* Layout for bit use in `marked' field: */ 87 #define WHITE0BIT 0 /* object is white (type 0) */ 88 #define WHITE1BIT 1 /* object is white (type 1) */ 89 #define BLACKBIT 2 /* object is black */ 90 #define FINALIZEDBIT 3 /* object has been separated for finalization */ 91 #define SEPARATED 4 /* object is in 'finobj' list or in 'tobefnz' */ 92 #define FIXEDBIT 5 /* object is fixed (should not be collected) */ 93 #define OLDBIT 6 /* object is old (only in generational mode) */ 94 /* bit 7 is currently used by tests (luaL_checkmemory) */ 95 96 #define WHITEBITS bit2mask(WHITE0BIT, WHITE1BIT) 97 98 99 #define iswhite(x) testbits((x)->gch.marked, WHITEBITS) 100 #define isblack(x) testbit((x)->gch.marked, BLACKBIT) 101 #define isgray(x) /* neither white nor black */ \ 102 (!testbits((x)->gch.marked, WHITEBITS | bitmask(BLACKBIT))) 103 104 #define isold(x) testbit((x)->gch.marked, OLDBIT) 105 106 /* MOVE OLD rule: whenever an object is moved to the beginning of 107 a GC list, its old bit must be cleared */ 108 #define resetoldbit(o) resetbit((o)->gch.marked, OLDBIT) 109 110 #define otherwhite(g) (g->currentwhite ^ WHITEBITS) 111 #define isdeadm(ow,m) (!(((m) ^ WHITEBITS) & (ow))) 112 #define isdead(g,v) isdeadm(otherwhite(g), (v)->gch.marked) 113 114 #define changewhite(x) ((x)->gch.marked ^= WHITEBITS) 115 #define gray2black(x) l_setbit((x)->gch.marked, BLACKBIT) 116 117 #define valiswhite(x) (iscollectable(x) && iswhite(gcvalue(x))) 118 119 #define luaC_white(g) cast(lu_byte, (g)->currentwhite & WHITEBITS) 120 121 122 #define luaC_condGC(L,c) \ 123 {if (G(L)->GCdebt > 0) {c;}; condchangemem(L);} 124 #define luaC_checkGC(L) luaC_condGC(L, luaC_step(L);) 125 126 127 #define luaC_barrier(L,p,v) { if (valiswhite(v) && isblack(obj2gco(p))) \ 128 luaC_barrier_(L,obj2gco(p),gcvalue(v)); } 129 130 #define luaC_barrierback(L,p,v) { if (valiswhite(v) && isblack(obj2gco(p))) \ 131 luaC_barrierback_(L,p); } 132 133 #define luaC_objbarrier(L,p,o) \ 134 { if (iswhite(obj2gco(o)) && isblack(obj2gco(p))) \ 135 luaC_barrier_(L,obj2gco(p),obj2gco(o)); } 136 137 #define luaC_objbarrierback(L,p,o) \ 138 { if (iswhite(obj2gco(o)) && isblack(obj2gco(p))) luaC_barrierback_(L,p); } 139 140 #define luaC_barrierproto(L,p,c) \ 141 { if (isblack(obj2gco(p))) luaC_barrierproto_(L,p,c); } 142 143 LUAI_FUNC void luaC_freeallobjects (lua_State *L); 144 LUAI_FUNC void luaC_step (lua_State *L); 145 LUAI_FUNC void luaC_forcestep (lua_State *L); 146 LUAI_FUNC void luaC_runtilstate (lua_State *L, int statesmask); 147 LUAI_FUNC void luaC_fullgc (lua_State *L, int isemergency); 148 LUAI_FUNC GCObject *luaC_newobj (lua_State *L, int tt, size_t sz, 149 GCObject **list, int offset); 150 LUAI_FUNC void luaC_barrier_ (lua_State *L, GCObject *o, GCObject *v); 151 LUAI_FUNC void luaC_barrierback_ (lua_State *L, GCObject *o); 152 LUAI_FUNC void luaC_barrierproto_ (lua_State *L, Proto *p, Closure *c); 153 LUAI_FUNC void luaC_checkfinalizer (lua_State *L, GCObject *o, Table *mt); 154 LUAI_FUNC void luaC_checkupvalcolor (global_State *g, UpVal *uv); 155 LUAI_FUNC void luaC_changemode (lua_State *L, int mode); 156 157 #endif 158