/* Kernel thread helper functions.
* Copyright (C) 2004 IBM Corporation, Rusty Russell.
*
- * Creation is done via keventd, so that we get a clean environment
+ * Creation is done via kthreadd, so that we get a clean environment
* even if we're invoked from userspace (think modprobe, hotplug cpu,
* etc.).
*/
#include <linux/kthread.h>
#include <linux/completion.h>
#include <linux/err.h>
+#include <linux/cpuset.h>
#include <linux/unistd.h>
#include <linux/file.h>
#include <linux/module.h>
#include <linux/mutex.h>
-#include <asm/semaphore.h>
+#include <trace/events/sched.h>
-/*
- * We dont want to execute off keventd since it might
- * hold a semaphore our callers hold too:
- */
-static struct workqueue_struct *helper_wq;
+static DEFINE_SPINLOCK(kthread_create_lock);
+static LIST_HEAD(kthread_create_list);
+struct task_struct *kthreadd_task;
struct kthread_create_info
{
- /* Information passed to kthread() from keventd. */
+ /* Information passed to kthread() from kthreadd. */
int (*threadfn)(void *data);
void *data;
- struct completion started;
- /* Result passed back to kthread_create() from keventd. */
+ /* Result passed back to kthread_create() from kthreadd. */
struct task_struct *result;
struct completion done;
+
+ struct list_head list;
};
-struct kthread_stop_info
-{
- struct task_struct *k;
- int err;
- struct completion done;
+struct kthread {
+ int should_stop;
+ struct completion exited;
};
-/* Thread stopping is done by setthing this var: lock serializes
- * multiple kthread_stop calls. */
-static DEFINE_MUTEX(kthread_stop_lock);
-static struct kthread_stop_info kthread_stop_info;
+#define to_kthread(tsk) \
+ container_of((tsk)->vfork_done, struct kthread, exited)
+/**
+ * kthread_should_stop - should this kthread return now?
+ *
+ * When someone calls kthread_stop() on your kthread, it will be woken
+ * and this will return true. You should then return, and your return
+ * value will be passed through to kthread_stop().
+ */
int kthread_should_stop(void)
{
- return (kthread_stop_info.k == current);
+ return to_kthread(current)->should_stop;
}
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)
{
+ /* Copy data: it's on kthread's stack */
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);
+ int (*threadfn)(void *data) = create->threadfn;
+ void *data = create->data;
+ struct kthread self;
+ int ret;
- /* By default we can run anywhere, unlike keventd. */
- set_cpus_allowed(current, CPU_MASK_ALL);
+ self.should_stop = 0;
+ init_completion(&self.exited);
+ current->vfork_done = &self.exited;
/* OK, tell user we're spawned, wait for stop or wakeup */
- __set_current_state(TASK_INTERRUPTIBLE);
- complete(&create->started);
+ __set_current_state(TASK_UNINTERRUPTIBLE);
+ create->result = current;
+ complete(&create->done);
schedule();
- if (!kthread_should_stop())
+ ret = -EINTR;
+ if (!self.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 can't just return, we must preserve "self" on stack */
+ do_exit(ret);
}
-/* We are keventd: create a thread. */
-static void keventd_create_kthread(void *_create)
+static void create_kthread(struct kthread_create_info *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);
}
- complete(&create->done);
}
+/**
+ * kthread_create - create a kthread.
+ * @threadfn: the function to run until signal_pending(current).
+ * @data: data ptr for @threadfn.
+ * @namefmt: printf-style name for the thread.
+ *
+ * Description: This helper function creates and names a kernel
+ * thread. The thread will be stopped: use wake_up_process() to start
+ * it. See also kthread_run(), kthread_create_on_cpu().
+ *
+ * When woken, the thread will run @threadfn() with @data as its
+ * argument. @threadfn() can either call do_exit() directly if it is a
+ * standalone thread for which noone will call kthread_stop(), or
+ * return when 'kthread_should_stop()' is true (which means
+ * kthread_stop() has been called). The return value should be zero
+ * or a negative error number; it will be passed to kthread_stop().
+ *
+ * Returns a task_struct or ERR_PTR(-ENOMEM).
+ */
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);
- }
+ spin_lock(&kthread_create_lock);
+ list_add_tail(&create.list, &kthread_create_list);
+ spin_unlock(&kthread_create_lock);
+
+ wake_up_process(kthreadd_task);
+ wait_for_completion(&create.done);
+
if (!IS_ERR(create.result)) {
+ struct sched_param param = { .sched_priority = 0 };
va_list args;
+
va_start(args, namefmt);
vsnprintf(create.result->comm, sizeof(create.result->comm),
namefmt, args);
va_end(args);
+ /*
+ * root may have changed our (kthreadd's) priority or CPU mask.
+ * The kernel thread should not inherit these properties.
+ */
+ sched_setscheduler_nocheck(create.result, SCHED_NORMAL, ¶m);
+ set_cpus_allowed_ptr(create.result, cpu_all_mask);
}
-
return create.result;
}
EXPORT_SYMBOL(kthread_create);
-void kthread_bind(struct task_struct *k, unsigned int cpu)
+/**
+ * kthread_bind - bind a just-created kthread to a cpu.
+ * @p: thread created by kthread_create().
+ * @cpu: cpu (might not be online, must be possible) for @k to run on.
+ *
+ * Description: This function is equivalent to set_cpus_allowed(),
+ * except that @cpu doesn't need to be online, and the thread must be
+ * stopped (i.e., just returned from kthread_create()).
+ */
+void kthread_bind(struct task_struct *p, 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);
+ if (!wait_task_inactive(p, TASK_UNINTERRUPTIBLE)) {
+ WARN_ON(1);
+ return;
+ }
+
+ p->cpus_allowed = cpumask_of_cpu(cpu);
+ p->rt.nr_cpus_allowed = 1;
+ p->flags |= PF_THREAD_BOUND;
}
EXPORT_SYMBOL(kthread_bind);
+/**
+ * kthread_stop - stop a thread created by kthread_create().
+ * @k: thread created by kthread_create().
+ *
+ * Sets kthread_should_stop() for @k to return true, wakes it, and
+ * waits for it to exit. This can also be called after kthread_create()
+ * instead of calling wake_up_process(): the thread will exit without
+ * calling threadfn().
+ *
+ * If threadfn() may call do_exit() itself, the caller must ensure
+ * task_struct can't go away.
+ *
+ * Returns the result of threadfn(), or %-EINTR if wake_up_process()
+ * was never called.
+ */
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)
-{
+ struct kthread *kthread;
int ret;
- mutex_lock(&kthread_stop_lock);
-
- /* It could exit after stop_info.k set, but before wake_up_process. */
+ trace_sched_kthread_stop(k);
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
+ kthread = to_kthread(k);
+ barrier(); /* it might have exited */
+ if (k->vfork_done != NULL) {
+ kthread->should_stop = 1;
wake_up_process(k);
- put_task_struct(k);
+ wait_for_completion(&kthread->exited);
+ }
+ ret = k->exit_code;
- /* 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;
- mutex_unlock(&kthread_stop_lock);
+ put_task_struct(k);
+ trace_sched_kthread_stop_ret(ret);
return ret;
}
-EXPORT_SYMBOL(kthread_stop_sem);
+EXPORT_SYMBOL(kthread_stop);
-static __init int helper_init(void)
+int kthreadd(void *unused)
{
- helper_wq = create_singlethread_workqueue("kthread");
- BUG_ON(!helper_wq);
+ struct task_struct *tsk = current;
+
+ /* Setup a clean context for our children to inherit. */
+ set_task_comm(tsk, "kthreadd");
+ ignore_signals(tsk);
+ set_cpus_allowed_ptr(tsk, cpu_all_mask);
+ set_mems_allowed(node_possible_map);
+
+ current->flags |= PF_NOFREEZE | PF_FREEZER_NOSIG;
+
+ for (;;) {
+ set_current_state(TASK_INTERRUPTIBLE);
+ if (list_empty(&kthread_create_list))
+ schedule();
+ __set_current_state(TASK_RUNNING);
+
+ spin_lock(&kthread_create_lock);
+ while (!list_empty(&kthread_create_list)) {
+ struct kthread_create_info *create;
+
+ create = list_entry(kthread_create_list.next,
+ struct kthread_create_info, list);
+ list_del_init(&create->list);
+ spin_unlock(&kthread_create_lock);
+
+ create_kthread(create);
+
+ spin_lock(&kthread_create_lock);
+ }
+ spin_unlock(&kthread_create_lock);
+ }
return 0;
}
-core_initcall(helper_init);
-
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