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