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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 |