1/*
2** $Id: lgc.h $
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 means
16** the object is not marked; gray, which means the object is marked, but
17** its references may be not marked; and black, which means that the
18** object and all its references are marked. The main invariant of the
19** garbage collector, while marking objects, is that a black object can
20** never point to a white one. Moreover, any gray object must be in a
21** "gray list" (gray, grayagain, weak, allweak, ephemeron) so that it
22** can be visited again before finishing the collection cycle. (Open
23** upvalues are an exception to this rule.) These lists have no meaning
24** when the invariant is not being enforced (e.g., sweep phase).
25*/
26
27
28/*
29** Possible states of the Garbage Collector
30*/
31#define GCSpropagate 0
32#define GCSenteratomic 1
33#define GCSatomic 2
34#define GCSswpallgc 3
35#define GCSswpfinobj 4
36#define GCSswptobefnz 5
37#define GCSswpend 6
38#define GCScallfin 7
39#define GCSpause 8
40
41
42#define issweepphase(g) \
43 (GCSswpallgc <= (g)->gcstate && (g)->gcstate <= GCSswpend)
44
45
46/*
47** macro to tell when main invariant (white objects cannot point to black
48** ones) must be kept. During a collection, the sweep
49** phase may break the invariant, as objects turned white may point to
50** still-black objects. The invariant is restored when sweep ends and
51** all objects are white again.
52*/
53
54#define keepinvariant(g) ((g)->gcstate <= GCSatomic)
55
56
57/*
58** some useful bit tricks
59*/
60#define resetbits(x,m) ((x) &= cast_byte(~(m)))
61#define setbits(x,m) ((x) |= (m))
62#define testbits(x,m) ((x) & (m))
63#define bitmask(b) (1<<(b))
64#define bit2mask(b1,b2) (bitmask(b1) | bitmask(b2))
65#define l_setbit(x,b) setbits(x, bitmask(b))
66#define resetbit(x,b) resetbits(x, bitmask(b))
67#define testbit(x,b) testbits(x, bitmask(b))
68
69
70/*
71** Layout for bit use in 'marked' field. First three bits are
72** used for object "age" in generational mode. Last bit is used
73** by tests.
74*/
75#define WHITE0BIT 3 /* object is white (type 0) */
76#define WHITE1BIT 4 /* object is white (type 1) */
77#define BLACKBIT 5 /* object is black */
78#define FINALIZEDBIT 6 /* object has been marked for finalization */
79
80#define TESTBIT 7
81
82
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) & (ow))
96#define isdead(g,v) isdeadm(otherwhite(g), (v)->marked)
97
98#define changewhite(x) ((x)->marked ^= WHITEBITS)
99#define nw2black(x) \
100 check_exp(!iswhite(x), l_setbit((x)->marked, BLACKBIT))
101
102#define luaC_white(g) cast_byte((g)->currentwhite & WHITEBITS)
103
104
105/* object age in generational mode */
106#define G_NEW 0 /* created in current cycle */
107#define G_SURVIVAL 1 /* created in previous cycle */
108#define G_OLD0 2 /* marked old by frw. barrier in this cycle */
109#define G_OLD1 3 /* first full cycle as old */
110#define G_OLD 4 /* really old object (not to be visited) */
111#define G_TOUCHED1 5 /* old object touched this cycle */
112#define G_TOUCHED2 6 /* old object touched in previous cycle */
113
114#define AGEBITS 7 /* all age bits (111) */
115
116#define getage(o) ((o)->marked & AGEBITS)
117#define setage(o,a) ((o)->marked = cast_byte(((o)->marked & (~AGEBITS)) | a))
118#define isold(o) (getage(o) > G_SURVIVAL)
119
120#define changeage(o,f,t) \
121 check_exp(getage(o) == (f), (o)->marked ^= ((f)^(t)))
122
123
124/* Default Values for GC parameters */
125#define LUAI_GENMAJORMUL 100
126#define LUAI_GENMINORMUL 20
127
128/* wait memory to double before starting new cycle */
129#define LUAI_GCPAUSE 200
130
131/*
132** some gc parameters are stored divided by 4 to allow a maximum value
133** up to 1023 in a 'lu_byte'.
134*/
135#define getgcparam(p) ((p) * 4)
136#define setgcparam(p,v) ((p) = (v) / 4)
137
138#define LUAI_GCMUL 100
139
140/* how much to allocate before next GC step (log2) */
141#define LUAI_GCSTEPSIZE 13 /* 8 KB */
142
143
144/*
145** Check whether the declared GC mode is generational. While in
146** generational mode, the collector can go temporarily to incremental
147** mode to improve performance. This is signaled by 'g->lastatomic != 0'.
148*/
149#define isdecGCmodegen(g) (g->gckind == KGC_GEN || g->lastatomic != 0)
150
151
152/*
153** Control when GC is running:
154*/
155#define GCSTPUSR 1 /* bit true when GC stopped by user */
156#define GCSTPGC 2 /* bit true when GC stopped by itself */
157#define GCSTPCLS 4 /* bit true when closing Lua state */
158#define gcrunning(g) ((g)->gcstp == 0)
159
160
161/*
162** Does one step of collection when debt becomes positive. 'pre'/'pos'
163** allows some adjustments to be done only when needed. macro
164** 'condchangemem' is used only for heavy tests (forcing a full
165** GC cycle on every opportunity)
166*/
167#define luaC_condGC(L,pre,pos) \
168 { if (G(L)->GCdebt > 0) { pre; luaC_step(L); pos;}; \
169 condchangemem(L,pre,pos); }
170
171/* more often than not, 'pre'/'pos' are empty */
172#define luaC_checkGC(L) luaC_condGC(L,(void)0,(void)0)
173
174
175#define luaC_barrier(L,p,v) ( \
176 (iscollectable(v) && isblack(p) && iswhite(gcvalue(v))) ? \
177 luaC_barrier_(L,obj2gco(p),gcvalue(v)) : cast_void(0))
178
179#define luaC_barrierback(L,p,v) ( \
180 (iscollectable(v) && isblack(p) && iswhite(gcvalue(v))) ? \
181 luaC_barrierback_(L,p) : cast_void(0))
182
183#define luaC_objbarrier(L,p,o) ( \
184 (isblack(p) && iswhite(o)) ? \
185 luaC_barrier_(L,obj2gco(p),obj2gco(o)) : cast_void(0))
186
187LUAI_FUNC void luaC_fix (lua_State *L, GCObject *o);
188LUAI_FUNC void luaC_freeallobjects (lua_State *L);
189LUAI_FUNC void luaC_step (lua_State *L);
190LUAI_FUNC void luaC_runtilstate (lua_State *L, int statesmask);
191LUAI_FUNC void luaC_fullgc (lua_State *L, int isemergency);
192LUAI_FUNC GCObject *luaC_newobj (lua_State *L, int tt, size_t sz);
193LUAI_FUNC void luaC_barrier_ (lua_State *L, GCObject *o, GCObject *v);
194LUAI_FUNC void luaC_barrierback_ (lua_State *L, GCObject *o);
195LUAI_FUNC void luaC_checkfinalizer (lua_State *L, GCObject *o, Table *mt);
196LUAI_FUNC void luaC_changemode (lua_State *L, int newmode);
197
198
199#endif
200