/* 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) { return kthread_stop_sem(k, NULL); } EXPORT_SYMBOL(kthread_stop); int kthread_stop_sem(struct task_struct *k, struct semaphore *s) { 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); smp_wmb(); /* Now set kthread_should_stop() to true, and wake it up. */ kthread_stop_info.k = k; if (s) up(s); else 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_sem); static __init int helper_init(void) { helper_wq = create_singlethread_workqueue("kthread"); BUG_ON(!helper_wq); return 0; } core_initcall(helper_init);