1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
|
/*
* Is nothing simple?
*
* We can't free the stack until we've finished executing,
* but once we've finished executing, we can't do anything
* at all, including call free. So instead we keep a linked list
* of all stacks for all processes, and every few times we try
* to allocate a new stack we scan the current stack list for
* dead processes and reclaim those stacks.
*/
#include <u.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sched.h>
#include <signal.h>
#include <errno.h>
#include <libc.h>
#include "9proc.h"
int fforkstacksize = 16384;
typedef struct Stack Stack;
struct Stack
{
Stack *next;
Stack *fnext;
int pid;
};
static Lock stacklock;
static Stack *freestacks;
static Stack *allstacks;
static int stackmallocs;
static void gc(void);
static void*
mallocstack(void)
{
Stack *p;
lock(&stacklock);
top:
p = freestacks;
if(p)
freestacks = p->fnext;
else{
if(stackmallocs++%1 == 0)
gc();
if(freestacks)
goto top;
p = malloc(fforkstacksize);
p->next = allstacks;
allstacks = p;
}
if(p)
p->pid = 1;
unlock(&stacklock);
return p;
}
static void
gc(void)
{
Stack *p;
for(p=allstacks; p; p=p->next){
if(p->pid > 1)
if(kill(p->pid, 0) < 0 && errno == ESRCH){
if(0) fprint(2, "reclaim stack from %d\n", p->pid);
p->pid = 0;
}
if(p->pid == 0){
p->fnext = freestacks;
freestacks = p;
}
}
}
static void
freestack(void *v)
{
Stack *p;
p = v;
if(p == nil)
return;
lock(&stacklock);
p->fnext = freestacks;
p->pid = 0;
freestacks = p;
unlock(&stacklock);
return;
}
static int
tramp(void *v)
{
void (*fn)(void*), *arg;
void **v2;
void *p;
_p9uproc(0);
v2 = v;
fn = v2[0];
arg = v2[1];
p = v2[2];
free(v2);
fn(arg);
_exit(0);
return 0;
}
static int
trampnowait(void *v)
{
int pid;
int cloneflag;
void **v2;
int *pidp;
void *p;
v2 = v;
cloneflag = (int)v2[4];
pidp = v2[3];
p = v2[2];
pid = clone(tramp, p+fforkstacksize-512, cloneflag, v);
*pidp = pid;
_exit(0);
return 0;
}
int
ffork(int flags, void (*fn)(void*), void *arg)
{
void **v;
char *p;
int cloneflag, pid, thepid, status, nowait;
_p9uproc(0);
p = mallocstack();
v = malloc(sizeof(void*)*5);
if(p==nil || v==nil){
freestack(p);
free(v);
return -1;
}
cloneflag = 0;
flags &= ~RFPROC;
if(flags&RFMEM){
cloneflag |= CLONE_VM;
flags &= ~RFMEM;
}
if(!(flags&RFFDG))
cloneflag |= CLONE_FILES;
else
flags &= ~RFFDG;
nowait = flags&RFNOWAIT;
if(!(flags&RFNOWAIT))
cloneflag |= SIGCHLD;
else
flags &= ~RFNOWAIT;
if(flags){
fprint(2, "unknown rfork flags %x\n", flags);
freestack(p);
free(v);
return -1;
}
v[0] = fn;
v[1] = arg;
v[2] = p;
v[3] = &thepid;
v[4] = (void*)cloneflag;
thepid = -1;
pid = clone(nowait ? trampnowait : tramp, p+fforkstacksize-16, cloneflag, v);
if(pid > 0 && nowait){
if(wait4(pid, &status, __WALL, 0) < 0)
fprint(2, "ffork wait4: %r\n");
}else
thepid = pid;
if(thepid == -1)
freestack(p);
else
((Stack*)p)->pid = thepid;
return thepid;
}
int
getfforkid(void)
{
return getpid();
}
|