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
194
195
196
197
198
199
200
201
202
|
/* Kernel thread helper functions.
* Copyright (C) 2004 IBM Corporation, Rusty Russell.
*
* Creation is done via keventd, so that we get a clean environment
* even if we're invoked from userspace (think modprobe, hotplug cpu,
* etc.).
*/
#include <linux/sched.h>
#include <linux/kthread.h>
#include <linux/completion.h>
#include <linux/err.h>
#include <linux/unistd.h>
#include <linux/file.h>
#include <linux/module.h>
#include <asm/semaphore.h>
/*
* We dont want to execute off keventd since it might
* hold a semaphore our callers hold too:
*/
static struct workqueue_struct *helper_wq;
struct kthread_create_info
{
/* Information passed to kthread() from keventd. */
int (*threadfn)(void *data);
void *data;
struct completion started;
/* Result passed back to kthread_create() from keventd. */
struct task_struct *result;
struct completion done;
};
struct kthread_stop_info
{
struct task_struct *k;
int err;
struct completion done;
};
/* Thread stopping is done by setthing this var: lock serializes
* multiple kthread_stop calls. */
static DECLARE_MUTEX(kthread_stop_lock);
static struct kthread_stop_info kthread_stop_info;
int kthread_should_stop(void)
{
return (kthread_stop_info.k == current);
}
EXPORT_SYMBOL(kthread_should_stop);
static void kthread_exit_files(void)
{
struct fs_struct *fs;
struct task_struct *tsk = current;
exit_fs(tsk); /* current->fs->count--; */
fs = init_task.fs;
tsk->fs = fs;
atomic_inc(&fs->count);
exit_files(tsk);
current->files = init_task.files;
atomic_inc(&tsk->files->count);
}
static int kthread(void *_create)
{
struct kthread_create_info *create = _create;
int (*threadfn)(void *data);
void *data;
sigset_t blocked;
int ret = -EINTR;
kthread_exit_files();
/* Copy data: it's on keventd's stack */
threadfn = create->threadfn;
data = create->data;
/* Block and flush all signals (in case we're not from keventd). */
sigfillset(&blocked);
sigprocmask(SIG_BLOCK, &blocked, NULL);
flush_signals(current);
/* By default we can run anywhere, unlike keventd. */
set_cpus_allowed(current, CPU_MASK_ALL);
/* OK, tell user we're spawned, wait for stop or wakeup */
__set_current_state(TASK_INTERRUPTIBLE);
complete(&create->started);
schedule();
if (!kthread_should_stop())
ret = threadfn(data);
/* It might have exited on its own, w/o kthread_stop. Check. */
if (kthread_should_stop()) {
kthread_stop_info.err = ret;
complete(&kthread_stop_info.done);
}
return 0;
}
/* We are keventd: create a thread. */
static void keventd_create_kthread(void *_create)
{
struct kthread_create_info *create = _create;
int pid;
/* We want our own signal handler (we take no signals by default). */
pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD);
if (pid < 0) {
create->result = ERR_PTR(pid);
} else {
wait_for_completion(&create->started);
create->result = find_task_by_pid(pid);
}
complete(&create->done);
}
struct task_struct *kthread_create(int (*threadfn)(void *data),
void *data,
const char namefmt[],
...)
{
struct kthread_create_info create;
DECLARE_WORK(work, keventd_create_kthread, &create);
create.threadfn = threadfn;
create.data = data;
init_completion(&create.started);
init_completion(&create.done);
/*
* The workqueue needs to start up first:
*/
if (!helper_wq)
work.func(work.data);
else {
queue_work(helper_wq, &work);
wait_for_completion(&create.done);
}
if (!IS_ERR(create.result)) {
va_list args;
va_start(args, namefmt);
vsnprintf(create.result->comm, sizeof(create.result->comm),
namefmt, args);
va_end(args);
}
return create.result;
}
EXPORT_SYMBOL(kthread_create);
void kthread_bind(struct task_struct *k, unsigned int cpu)
{
BUG_ON(k->state != TASK_INTERRUPTIBLE);
/* Must have done schedule() in kthread() before we set_task_cpu */
wait_task_inactive(k);
set_task_cpu(k, cpu);
k->cpus_allowed = cpumask_of_cpu(cpu);
}
EXPORT_SYMBOL(kthread_bind);
int kthread_stop(struct task_struct *k)
{
int ret;
down(&kthread_stop_lock);
/* It could exit after stop_info.k set, but before wake_up_process. */
get_task_struct(k);
/* Must init completion *before* thread sees kthread_stop_info.k */
init_completion(&kthread_stop_info.done);
wmb();
/* Now set kthread_should_stop() to true, and wake it up. */
kthread_stop_info.k = k;
wake_up_process(k);
put_task_struct(k);
/* Once it dies, reset stop ptr, gather result and we're done. */
wait_for_completion(&kthread_stop_info.done);
kthread_stop_info.k = NULL;
ret = kthread_stop_info.err;
up(&kthread_stop_lock);
return ret;
}
EXPORT_SYMBOL(kthread_stop);
static __init int helper_init(void)
{
helper_wq = create_singlethread_workqueue("kthread");
BUG_ON(!helper_wq);
return 0;
}
core_initcall(helper_init);
|
