| 1 | /* |
| 2 | ** $Id: lgc.h,v 2.58 2012/09/11 12:53:08 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 |