Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 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 <asm/semaphore.h> |
| 16 | |
| 17 | /* |
| 18 | * We dont want to execute off keventd since it might |
| 19 | * hold a semaphore our callers hold too: |
| 20 | */ |
| 21 | static struct workqueue_struct *helper_wq; |
| 22 | |
| 23 | struct kthread_create_info |
| 24 | { |
| 25 | /* Information passed to kthread() from keventd. */ |
| 26 | int (*threadfn)(void *data); |
| 27 | void *data; |
| 28 | struct completion started; |
| 29 | |
| 30 | /* Result passed back to kthread_create() from keventd. */ |
| 31 | struct task_struct *result; |
| 32 | struct completion done; |
| 33 | }; |
| 34 | |
| 35 | struct kthread_stop_info |
| 36 | { |
| 37 | struct task_struct *k; |
| 38 | int err; |
| 39 | struct completion done; |
| 40 | }; |
| 41 | |
| 42 | /* Thread stopping is done by setthing this var: lock serializes |
| 43 | * multiple kthread_stop calls. */ |
| 44 | static DECLARE_MUTEX(kthread_stop_lock); |
| 45 | static struct kthread_stop_info kthread_stop_info; |
| 46 | |
| 47 | int kthread_should_stop(void) |
| 48 | { |
| 49 | return (kthread_stop_info.k == current); |
| 50 | } |
| 51 | EXPORT_SYMBOL(kthread_should_stop); |
| 52 | |
| 53 | static void kthread_exit_files(void) |
| 54 | { |
| 55 | struct fs_struct *fs; |
| 56 | struct task_struct *tsk = current; |
| 57 | |
| 58 | exit_fs(tsk); /* current->fs->count--; */ |
| 59 | fs = init_task.fs; |
| 60 | tsk->fs = fs; |
| 61 | atomic_inc(&fs->count); |
| 62 | exit_files(tsk); |
| 63 | current->files = init_task.files; |
| 64 | atomic_inc(&tsk->files->count); |
| 65 | } |
| 66 | |
| 67 | static int kthread(void *_create) |
| 68 | { |
| 69 | struct kthread_create_info *create = _create; |
| 70 | int (*threadfn)(void *data); |
| 71 | void *data; |
| 72 | sigset_t blocked; |
| 73 | int ret = -EINTR; |
| 74 | |
| 75 | kthread_exit_files(); |
| 76 | |
| 77 | /* Copy data: it's on keventd's stack */ |
| 78 | threadfn = create->threadfn; |
| 79 | data = create->data; |
| 80 | |
| 81 | /* Block and flush all signals (in case we're not from keventd). */ |
| 82 | sigfillset(&blocked); |
| 83 | sigprocmask(SIG_BLOCK, &blocked, NULL); |
| 84 | flush_signals(current); |
| 85 | |
| 86 | /* By default we can run anywhere, unlike keventd. */ |
| 87 | set_cpus_allowed(current, CPU_MASK_ALL); |
| 88 | |
| 89 | /* OK, tell user we're spawned, wait for stop or wakeup */ |
| 90 | __set_current_state(TASK_INTERRUPTIBLE); |
| 91 | complete(&create->started); |
| 92 | schedule(); |
| 93 | |
| 94 | if (!kthread_should_stop()) |
| 95 | ret = threadfn(data); |
| 96 | |
| 97 | /* It might have exited on its own, w/o kthread_stop. Check. */ |
| 98 | if (kthread_should_stop()) { |
| 99 | kthread_stop_info.err = ret; |
| 100 | complete(&kthread_stop_info.done); |
| 101 | } |
| 102 | return 0; |
| 103 | } |
| 104 | |
| 105 | /* We are keventd: create a thread. */ |
| 106 | static void keventd_create_kthread(void *_create) |
| 107 | { |
| 108 | struct kthread_create_info *create = _create; |
| 109 | int pid; |
| 110 | |
| 111 | /* We want our own signal handler (we take no signals by default). */ |
| 112 | pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD); |
| 113 | if (pid < 0) { |
| 114 | create->result = ERR_PTR(pid); |
| 115 | } else { |
| 116 | wait_for_completion(&create->started); |
| 117 | create->result = find_task_by_pid(pid); |
| 118 | } |
| 119 | complete(&create->done); |
| 120 | } |
| 121 | |
| 122 | struct task_struct *kthread_create(int (*threadfn)(void *data), |
| 123 | void *data, |
| 124 | const char namefmt[], |
| 125 | ...) |
| 126 | { |
| 127 | struct kthread_create_info create; |
| 128 | DECLARE_WORK(work, keventd_create_kthread, &create); |
| 129 | |
| 130 | create.threadfn = threadfn; |
| 131 | create.data = data; |
| 132 | init_completion(&create.started); |
| 133 | init_completion(&create.done); |
| 134 | |
| 135 | /* |
| 136 | * The workqueue needs to start up first: |
| 137 | */ |
| 138 | if (!helper_wq) |
| 139 | work.func(work.data); |
| 140 | else { |
| 141 | queue_work(helper_wq, &work); |
| 142 | wait_for_completion(&create.done); |
| 143 | } |
| 144 | if (!IS_ERR(create.result)) { |
| 145 | va_list args; |
| 146 | va_start(args, namefmt); |
| 147 | vsnprintf(create.result->comm, sizeof(create.result->comm), |
| 148 | namefmt, args); |
| 149 | va_end(args); |
| 150 | } |
| 151 | |
| 152 | return create.result; |
| 153 | } |
| 154 | EXPORT_SYMBOL(kthread_create); |
| 155 | |
| 156 | void kthread_bind(struct task_struct *k, unsigned int cpu) |
| 157 | { |
| 158 | BUG_ON(k->state != TASK_INTERRUPTIBLE); |
| 159 | /* Must have done schedule() in kthread() before we set_task_cpu */ |
| 160 | wait_task_inactive(k); |
| 161 | set_task_cpu(k, cpu); |
| 162 | k->cpus_allowed = cpumask_of_cpu(cpu); |
| 163 | } |
| 164 | EXPORT_SYMBOL(kthread_bind); |
| 165 | |
| 166 | int kthread_stop(struct task_struct *k) |
| 167 | { |
| 168 | int ret; |
| 169 | |
| 170 | down(&kthread_stop_lock); |
| 171 | |
| 172 | /* It could exit after stop_info.k set, but before wake_up_process. */ |
| 173 | get_task_struct(k); |
| 174 | |
| 175 | /* Must init completion *before* thread sees kthread_stop_info.k */ |
| 176 | init_completion(&kthread_stop_info.done); |
akpm@osdl.org | d59dd46 | 2005-05-01 08:58:47 -0700 | [diff] [blame] | 177 | smp_wmb(); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 178 | |
| 179 | /* Now set kthread_should_stop() to true, and wake it up. */ |
| 180 | kthread_stop_info.k = k; |
| 181 | wake_up_process(k); |
| 182 | put_task_struct(k); |
| 183 | |
| 184 | /* Once it dies, reset stop ptr, gather result and we're done. */ |
| 185 | wait_for_completion(&kthread_stop_info.done); |
| 186 | kthread_stop_info.k = NULL; |
| 187 | ret = kthread_stop_info.err; |
| 188 | up(&kthread_stop_lock); |
| 189 | |
| 190 | return ret; |
| 191 | } |
| 192 | EXPORT_SYMBOL(kthread_stop); |
| 193 | |
| 194 | static __init int helper_init(void) |
| 195 | { |
| 196 | helper_wq = create_singlethread_workqueue("kthread"); |
| 197 | BUG_ON(!helper_wq); |
| 198 | |
| 199 | return 0; |
| 200 | } |
| 201 | core_initcall(helper_init); |
| 202 | |