ia64/linux-2.6.18-xen.hg

view kernel/kthread.c @ 912:dd42cdb0ab89

[IA64] Build blktap2 driver by default in x86 builds.

add CONFIG_XEN_BLKDEV_TAP2=y to buildconfigs/linux-defconfig_xen_ia64.

Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
author Isaku Yamahata <yamahata@valinux.co.jp>
date Mon Jun 29 12:09:16 2009 +0900 (2009-06-29)
parents 831230e53067
children
line source
1 /* Kernel thread helper functions.
2 * Copyright (C) 2004 IBM Corporation, Rusty Russell.
3 *
4 * Creation is done via keventd, 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/unistd.h>
13 #include <linux/file.h>
14 #include <linux/module.h>
15 #include <linux/mutex.h>
16 #include <asm/semaphore.h>
18 /*
19 * We dont want to execute off keventd since it might
20 * hold a semaphore our callers hold too:
21 */
22 static struct workqueue_struct *helper_wq;
24 struct kthread_create_info
25 {
26 /* Information passed to kthread() from keventd. */
27 int (*threadfn)(void *data);
28 void *data;
29 struct completion started;
31 /* Result passed back to kthread_create() from keventd. */
32 struct task_struct *result;
33 struct completion done;
34 };
36 struct kthread_stop_info
37 {
38 struct task_struct *k;
39 int err;
40 struct completion done;
41 };
43 /* Thread stopping is done by setthing this var: lock serializes
44 * multiple kthread_stop calls. */
45 static DEFINE_MUTEX(kthread_stop_lock);
46 static struct kthread_stop_info kthread_stop_info;
48 /**
49 * kthread_should_stop - should this kthread return now?
50 *
51 * When someone calls kthread_stop on your kthread, it will be woken
52 * and this will return true. You should then return, and your return
53 * value will be passed through to kthread_stop().
54 */
55 int kthread_should_stop(void)
56 {
57 return (kthread_stop_info.k == current);
58 }
59 EXPORT_SYMBOL(kthread_should_stop);
61 static void kthread_exit_files(void)
62 {
63 struct fs_struct *fs;
64 struct task_struct *tsk = current;
66 exit_fs(tsk); /* current->fs->count--; */
67 fs = init_task.fs;
68 tsk->fs = fs;
69 atomic_inc(&fs->count);
70 exit_files(tsk);
71 current->files = init_task.files;
72 atomic_inc(&tsk->files->count);
73 }
75 static int kthread(void *_create)
76 {
77 struct kthread_create_info *create = _create;
78 int (*threadfn)(void *data);
79 void *data;
80 sigset_t blocked;
81 int ret = -EINTR;
83 kthread_exit_files();
85 /* Copy data: it's on keventd's stack */
86 threadfn = create->threadfn;
87 data = create->data;
89 /* Block and flush all signals (in case we're not from keventd). */
90 sigfillset(&blocked);
91 sigprocmask(SIG_BLOCK, &blocked, NULL);
92 flush_signals(current);
94 /* By default we can run anywhere, unlike keventd. */
95 set_cpus_allowed(current, CPU_MASK_ALL);
97 /* OK, tell user we're spawned, wait for stop or wakeup */
98 __set_current_state(TASK_INTERRUPTIBLE);
99 complete(&create->started);
100 schedule();
102 if (!kthread_should_stop())
103 ret = threadfn(data);
105 /* It might have exited on its own, w/o kthread_stop. Check. */
106 if (kthread_should_stop()) {
107 kthread_stop_info.err = ret;
108 complete(&kthread_stop_info.done);
109 }
110 return 0;
111 }
113 /* We are keventd: create a thread. */
114 static void keventd_create_kthread(void *_create)
115 {
116 struct kthread_create_info *create = _create;
117 int pid;
119 /* We want our own signal handler (we take no signals by default). */
120 pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD);
121 if (pid < 0) {
122 create->result = ERR_PTR(pid);
123 } else {
124 wait_for_completion(&create->started);
125 read_lock(&tasklist_lock);
126 create->result = find_task_by_pid(pid);
127 read_unlock(&tasklist_lock);
128 }
129 complete(&create->done);
130 }
132 /**
133 * kthread_create - create a kthread.
134 * @threadfn: the function to run until signal_pending(current).
135 * @data: data ptr for @threadfn.
136 * @namefmt: printf-style name for the thread.
137 *
138 * Description: This helper function creates and names a kernel
139 * thread. The thread will be stopped: use wake_up_process() to start
140 * it. See also kthread_run(), kthread_create_on_cpu().
141 *
142 * When woken, the thread will run @threadfn() with @data as its
143 * argument. @threadfn can either call do_exit() directly if it is a
144 * standalone thread for which noone will call kthread_stop(), or
145 * return when 'kthread_should_stop()' is true (which means
146 * kthread_stop() has been called). The return value should be zero
147 * or a negative error number; it will be passed to kthread_stop().
148 *
149 * Returns a task_struct or ERR_PTR(-ENOMEM).
150 */
151 struct task_struct *kthread_create(int (*threadfn)(void *data),
152 void *data,
153 const char namefmt[],
154 ...)
155 {
156 struct kthread_create_info create;
157 DECLARE_WORK(work, keventd_create_kthread, &create);
159 create.threadfn = threadfn;
160 create.data = data;
161 init_completion(&create.started);
162 init_completion(&create.done);
164 /*
165 * The workqueue needs to start up first:
166 */
167 if (!helper_wq)
168 work.func(work.data);
169 else {
170 queue_work(helper_wq, &work);
171 wait_for_completion(&create.done);
172 }
173 if (!IS_ERR(create.result)) {
174 va_list args;
175 va_start(args, namefmt);
176 vsnprintf(create.result->comm, sizeof(create.result->comm),
177 namefmt, args);
178 va_end(args);
179 }
181 return create.result;
182 }
183 EXPORT_SYMBOL(kthread_create);
185 /**
186 * kthread_bind - bind a just-created kthread to a cpu.
187 * @k: thread created by kthread_create().
188 * @cpu: cpu (might not be online, must be possible) for @k to run on.
189 *
190 * Description: This function is equivalent to set_cpus_allowed(),
191 * except that @cpu doesn't need to be online, and the thread must be
192 * stopped (i.e., just returned from kthread_create().
193 */
194 void kthread_bind(struct task_struct *k, unsigned int cpu)
195 {
196 BUG_ON(k->state != TASK_INTERRUPTIBLE);
197 /* Must have done schedule() in kthread() before we set_task_cpu */
198 wait_task_inactive(k);
199 set_task_cpu(k, cpu);
200 k->cpus_allowed = cpumask_of_cpu(cpu);
201 }
202 EXPORT_SYMBOL(kthread_bind);
204 /**
205 * kthread_stop - stop a thread created by kthread_create().
206 * @k: thread created by kthread_create().
207 *
208 * Sets kthread_should_stop() for @k to return true, wakes it, and
209 * waits for it to exit. Your threadfn() must not call do_exit()
210 * itself if you use this function! This can also be called after
211 * kthread_create() instead of calling wake_up_process(): the thread
212 * will exit without calling threadfn().
213 *
214 * Returns the result of threadfn(), or %-EINTR if wake_up_process()
215 * was never called.
216 */
217 int kthread_stop(struct task_struct *k)
218 {
219 int ret;
221 mutex_lock(&kthread_stop_lock);
223 /* It could exit after stop_info.k set, but before wake_up_process. */
224 get_task_struct(k);
226 /* Must init completion *before* thread sees kthread_stop_info.k */
227 init_completion(&kthread_stop_info.done);
228 smp_wmb();
230 /* Now set kthread_should_stop() to true, and wake it up. */
231 kthread_stop_info.k = k;
232 wake_up_process(k);
233 put_task_struct(k);
235 /* Once it dies, reset stop ptr, gather result and we're done. */
236 wait_for_completion(&kthread_stop_info.done);
237 kthread_stop_info.k = NULL;
238 ret = kthread_stop_info.err;
239 mutex_unlock(&kthread_stop_lock);
241 return ret;
242 }
243 EXPORT_SYMBOL(kthread_stop);
245 static __init int helper_init(void)
246 {
247 helper_wq = create_singlethread_workqueue("kthread");
248 BUG_ON(!helper_wq);
250 return 0;
251 }
253 core_initcall(helper_init);