1 /*
2  * Proc structure hash table indexed by proctabid() (usually getpid()).
3  * No lock is necessary for lookups (important when called from signal
4  * handlers).
5  * 
6  * To be included from other files (e.g., Linux-clone.c).
7  */
8 
9 #define T ((void*)-1)
10 
11 enum
12 {
13 	PTABHASH = 1031,
14 };
15 
16 static Lock ptablock;
17 static Proc *proctab[PTABHASH];
18 static Proc *theproc;
19 static int multi;
20 
21 void
22 _threadmultiproc(void)
23 {
24 	if(multi == 0){
25 		multi = 1;
26 		_threadsetproc(theproc);
27 	}
28 }
29 
30 void
31 _threadsetproc(Proc *p)
32 {
33 	int i, h;
34 	Proc **t;
35 
36 	if(!multi){
37 		theproc = p;
38 		return;
39 	}
40 	lock(&ptablock);
41 	p->procid = procid();
42 	h = p->procid%PTABHASH;
43 	for(i=0; i<PTABHASH; i++){
44 		t = &proctab[(h+i)%PTABHASH];
45 		if(*t==nil || *t==T){
46 			*t = p;
47 			break;
48 		}
49 	}
50 	unlock(&ptablock);
51 	if(i == PTABHASH)
52 		sysfatal("too many procs - proctab is full");
53 }
54 
55 static Proc**
56 _threadfindproc(int id)
57 {
58 	int i, h;
59 	Proc **t;
60 
61 	if(!multi)
62 		return &theproc;
63 
64 	h = id%PTABHASH;
65 	for(i=0; i<PTABHASH; i++){
66 		t = &proctab[(h+i)%PTABHASH];
67 		if(*t != nil && *t != T && (*t)->procid == id){
68 			unlock(&ptablock);
69 			return t;
70 		}
71 	}
72 	return nil;
73 }
74 
75 Proc*
76 _threadgetproc(void)
77 {
78 	Proc **t;
79 
80 	t = _threadfindproc(procid());
81 	if(t == nil)
82 		return nil;
83 	return *t;
84 }
85 
86 Proc*
87 _threaddelproc(void)
88 {
89 	Proc **t, *p;
90 
91 	t = _threadfindproc(procid());
92 	if(t == nil)
93 		return nil;
94 	p = *t;
95 	*t = T;
96 	return p;
97 }