Root/kernel/kthread.c

1/* Kernel thread helper functions.
2 * Copyright (C) 2004 IBM Corporation, Rusty Russell.
3 *
4 * Creation is done via kthreadd, so that we get a clean environment
5 * even if we're invoked from userspace (think modprobe, hotplug cpu,
6 * etc.).
7 */
8#include <linux/sched.h>
9#include <linux/kthread.h>
10#include <linux/completion.h>
11#include <linux/err.h>
12#include <linux/cpuset.h>
13#include <linux/unistd.h>
14#include <linux/file.h>
15#include <linux/module.h>
16#include <linux/mutex.h>
17#include <trace/events/sched.h>
18
19static DEFINE_SPINLOCK(kthread_create_lock);
20static LIST_HEAD(kthread_create_list);
21struct task_struct *kthreadd_task;
22
23struct kthread_create_info
24{
25    /* Information passed to kthread() from kthreadd. */
26    int (*threadfn)(void *data);
27    void *data;
28
29    /* Result passed back to kthread_create() from kthreadd. */
30    struct task_struct *result;
31    struct completion done;
32
33    struct list_head list;
34};
35
36struct kthread {
37    int should_stop;
38    struct completion exited;
39};
40
41#define to_kthread(tsk) \
42    container_of((tsk)->vfork_done, struct kthread, exited)
43
44/**
45 * kthread_should_stop - should this kthread return now?
46 *
47 * When someone calls kthread_stop() on your kthread, it will be woken
48 * and this will return true. You should then return, and your return
49 * value will be passed through to kthread_stop().
50 */
51int kthread_should_stop(void)
52{
53    return to_kthread(current)->should_stop;
54}
55EXPORT_SYMBOL(kthread_should_stop);
56
57static int kthread(void *_create)
58{
59    /* Copy data: it's on kthread's stack */
60    struct kthread_create_info *create = _create;
61    int (*threadfn)(void *data) = create->threadfn;
62    void *data = create->data;
63    struct kthread self;
64    int ret;
65
66    self.should_stop = 0;
67    init_completion(&self.exited);
68    current->vfork_done = &self.exited;
69
70    /* OK, tell user we're spawned, wait for stop or wakeup */
71    __set_current_state(TASK_UNINTERRUPTIBLE);
72    create->result = current;
73    complete(&create->done);
74    schedule();
75
76    ret = -EINTR;
77    if (!self.should_stop)
78        ret = threadfn(data);
79
80    /* we can't just return, we must preserve "self" on stack */
81    do_exit(ret);
82}
83
84static void create_kthread(struct kthread_create_info *create)
85{
86    int pid;
87
88    /* We want our own signal handler (we take no signals by default). */
89    pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD);
90    if (pid < 0) {
91        create->result = ERR_PTR(pid);
92        complete(&create->done);
93    }
94}
95
96/**
97 * kthread_create - create a kthread.
98 * @threadfn: the function to run until signal_pending(current).
99 * @data: data ptr for @threadfn.
100 * @namefmt: printf-style name for the thread.
101 *
102 * Description: This helper function creates and names a kernel
103 * thread. The thread will be stopped: use wake_up_process() to start
104 * it. See also kthread_run().
105 *
106 * When woken, the thread will run @threadfn() with @data as its
107 * argument. @threadfn() can either call do_exit() directly if it is a
108 * standalone thread for which noone will call kthread_stop(), or
109 * return when 'kthread_should_stop()' is true (which means
110 * kthread_stop() has been called). The return value should be zero
111 * or a negative error number; it will be passed to kthread_stop().
112 *
113 * Returns a task_struct or ERR_PTR(-ENOMEM).
114 */
115struct task_struct *kthread_create(int (*threadfn)(void *data),
116                   void *data,
117                   const char namefmt[],
118                   ...)
119{
120    struct kthread_create_info create;
121
122    create.threadfn = threadfn;
123    create.data = data;
124    init_completion(&create.done);
125
126    spin_lock(&kthread_create_lock);
127    list_add_tail(&create.list, &kthread_create_list);
128    spin_unlock(&kthread_create_lock);
129
130    wake_up_process(kthreadd_task);
131    wait_for_completion(&create.done);
132
133    if (!IS_ERR(create.result)) {
134        struct sched_param param = { .sched_priority = 0 };
135        va_list args;
136
137        va_start(args, namefmt);
138        vsnprintf(create.result->comm, sizeof(create.result->comm),
139              namefmt, args);
140        va_end(args);
141        /*
142         * root may have changed our (kthreadd's) priority or CPU mask.
143         * The kernel thread should not inherit these properties.
144         */
145        sched_setscheduler_nocheck(create.result, SCHED_NORMAL, &param);
146        set_cpus_allowed_ptr(create.result, cpu_all_mask);
147    }
148    return create.result;
149}
150EXPORT_SYMBOL(kthread_create);
151
152/**
153 * kthread_bind - bind a just-created kthread to a cpu.
154 * @p: thread created by kthread_create().
155 * @cpu: cpu (might not be online, must be possible) for @k to run on.
156 *
157 * Description: This function is equivalent to set_cpus_allowed(),
158 * except that @cpu doesn't need to be online, and the thread must be
159 * stopped (i.e., just returned from kthread_create()).
160 */
161void kthread_bind(struct task_struct *p, unsigned int cpu)
162{
163    /* Must have done schedule() in kthread() before we set_task_cpu */
164    if (!wait_task_inactive(p, TASK_UNINTERRUPTIBLE)) {
165        WARN_ON(1);
166        return;
167    }
168
169    p->cpus_allowed = cpumask_of_cpu(cpu);
170    p->rt.nr_cpus_allowed = 1;
171    p->flags |= PF_THREAD_BOUND;
172}
173EXPORT_SYMBOL(kthread_bind);
174
175/**
176 * kthread_stop - stop a thread created by kthread_create().
177 * @k: thread created by kthread_create().
178 *
179 * Sets kthread_should_stop() for @k to return true, wakes it, and
180 * waits for it to exit. This can also be called after kthread_create()
181 * instead of calling wake_up_process(): the thread will exit without
182 * calling threadfn().
183 *
184 * If threadfn() may call do_exit() itself, the caller must ensure
185 * task_struct can't go away.
186 *
187 * Returns the result of threadfn(), or %-EINTR if wake_up_process()
188 * was never called.
189 */
190int kthread_stop(struct task_struct *k)
191{
192    struct kthread *kthread;
193    int ret;
194
195    trace_sched_kthread_stop(k);
196    get_task_struct(k);
197
198    kthread = to_kthread(k);
199    barrier(); /* it might have exited */
200    if (k->vfork_done != NULL) {
201        kthread->should_stop = 1;
202        wake_up_process(k);
203        wait_for_completion(&kthread->exited);
204    }
205    ret = k->exit_code;
206
207    put_task_struct(k);
208    trace_sched_kthread_stop_ret(ret);
209
210    return ret;
211}
212EXPORT_SYMBOL(kthread_stop);
213
214int kthreadd(void *unused)
215{
216    struct task_struct *tsk = current;
217
218    /* Setup a clean context for our children to inherit. */
219    set_task_comm(tsk, "kthreadd");
220    ignore_signals(tsk);
221    set_cpus_allowed_ptr(tsk, cpu_all_mask);
222    set_mems_allowed(node_states[N_HIGH_MEMORY]);
223
224    current->flags |= PF_NOFREEZE | PF_FREEZER_NOSIG;
225
226    for (;;) {
227        set_current_state(TASK_INTERRUPTIBLE);
228        if (list_empty(&kthread_create_list))
229            schedule();
230        __set_current_state(TASK_RUNNING);
231
232        spin_lock(&kthread_create_lock);
233        while (!list_empty(&kthread_create_list)) {
234            struct kthread_create_info *create;
235
236            create = list_entry(kthread_create_list.next,
237                        struct kthread_create_info, list);
238            list_del_init(&create->list);
239            spin_unlock(&kthread_create_lock);
240
241            create_kthread(create);
242
243            spin_lock(&kthread_create_lock);
244        }
245        spin_unlock(&kthread_create_lock);
246    }
247
248    return 0;
249}
250

Archive Download this file

Branches:
ben-wpan
ben-wpan-stefan
javiroman/ks7010
jz-2.6.34
jz-2.6.34-rc5
jz-2.6.34-rc6
jz-2.6.34-rc7
jz-2.6.35
jz-2.6.36
jz-2.6.37
jz-2.6.38
jz-2.6.39
jz-3.0
jz-3.1
jz-3.2
jz-3.3
jz-3.4
jz-3.5
jz-3.6
jz-3.6-rc2-pwm
jz-3.9
jz-3.9-clk
jz-3.9-rc8
jz47xx
jz47xx-2.6.38
master

Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
v2.6.34-rc6
v2.6.34-rc7
v3.9



interactive