1 static int fforkstacksize = 16384;
2 
3 typedef struct Stack Stack;
4 struct Stack
5 {
6 	Stack *next;
7 	Stack *fnext;
8 	int pid;
9 };
10 
11 static Lock stacklock;
12 static Stack *freestacks;
13 static Stack *allstacks;
14 static int stackmallocs;
15 static void gc(void);
16 
17 static void*
18 mallocstack(void)
19 {
20 	Stack *p;
21 
22 	lock(&stacklock);
23 top:
24 	p = freestacks;
25 	if(p)
26 		freestacks = p->fnext;
27 	else{
28 		if(stackmallocs++%1 == 0)
29 			gc();
30 		if(freestacks)
31 			goto top;
32 		p = malloc(fforkstacksize);
33 		p->next = allstacks;
34 		allstacks = p;
35 	}
36 	if(p)
37 		p->pid = 1;
38 	unlock(&stacklock);
39 	return p;
40 }
41 
42 static void
43 gc(void)
44 {
45 	Stack *p;
46 
47 	for(p=allstacks; p; p=p->next){
48 		if(p->pid > 1 && procexited(p->pid)){
49 			if(0) fprint(2, "reclaim stack from %d\n", p->pid);
50 			p->pid = 0;
51 		}
52 		if(p->pid == 0){
53 			p->fnext = freestacks;
54 			freestacks = p;
55 		}
56 	}
57 }
58 
59 static void
60 freestack(void *v)
61 {
62 	Stack *p;
63 
64 	p = v;
65 	if(p == nil)
66 		return;
67 	lock(&stacklock);
68 	p->fnext = freestacks;
69 	p->pid = 0;
70 	freestacks = p;
71 	unlock(&stacklock);
72 	return;
73 }
74 
75