/* 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 <linux/slab.h>
+#include <linux/freezer.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;
+ int node;
- /* 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;
+ void *data;
+ 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
+ * 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)
+/**
+ * kthread_data - return data value specified on kthread creation
+ * @task: kthread task in question
+ *
+ * Return the data value specified when kthread @task was created.
+ * The caller is responsible for ensuring the validity of @task when
+ * calling this function.
+ */
+void *kthread_data(struct task_struct *task)
{
- 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);
+ return to_kthread(task)->data;
}
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;
+ self.data = data;
+ 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)
+/* called from do_fork() to get node information for about to be created task */
+int tsk_fork_get_node(struct task_struct *tsk)
+{
+#ifdef CONFIG_NUMA
+ if (tsk == kthreadd_task)
+ return tsk->pref_node_fork;
+#endif
+ return numa_node_id();
+}
+
+static void create_kthread(struct kthread_create_info *create)
{
- struct kthread_create_info *create = _create;
int pid;
+#ifdef CONFIG_NUMA
+ current->pref_node_fork = create->node;
+#endif
/* 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);
- read_lock(&tasklist_lock);
- create->result = find_task_by_pid(pid);
- read_unlock(&tasklist_lock);
+ complete(&create->done);
}
- complete(&create->done);
}
/**
- * kthread_create - create a kthread.
+ * kthread_create_on_node - create a kthread.
* @threadfn: the function to run until signal_pending(current).
* @data: data ptr for @threadfn.
+ * @node: memory node number.
* @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().
+ * it. See also kthread_run().
*
+ * If thread is going to be bound on a particular cpu, give its node
+ * in @node, to get NUMA affinity for kthread stack, or else give -1.
* 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
+ * argument. @threadfn() can either call do_exit() directly if it is a
+ * standalone thread for which no one 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 task_struct *kthread_create_on_node(int (*threadfn)(void *data),
+ void *data,
+ int node,
+ 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);
+ create.node = node;
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)) {
+ static const 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);
+EXPORT_SYMBOL(kthread_create_on_node);
/**
* kthread_bind - bind a just-created kthread to a cpu.
- * @k: thread created by kthread_create().
+ * @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().
+ * stopped (i.e., just returned from kthread_create()).
*/
-void kthread_bind(struct task_struct *k, unsigned int cpu)
+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;
+ }
+
+ /* It's safe because the task is inactive. */
+ do_set_cpus_allowed(p, cpumask_of(cpu));
+ p->flags |= PF_THREAD_BOUND;
}
EXPORT_SYMBOL(kthread_bind);
* @k: thread created by kthread_create().
*
* Sets kthread_should_stop() for @k to return true, wakes it, and
- * waits for it to exit. Your threadfn() must not call do_exit()
- * itself if you use this function! This can also be called after
- * kthread_create() instead of calling wake_up_process(): the thread
- * will exit without calling threadfn().
+ * 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);
+ struct kthread *kthread;
+ int ret;
+
+ trace_sched_kthread_stop(k);
+ get_task_struct(k);
+
+ kthread = to_kthread(k);
+ barrier(); /* it might have exited */
+ if (k->vfork_done != NULL) {
+ kthread->should_stop = 1;
+ wake_up_process(k);
+ wait_for_completion(&kthread->exited);
+ }
+ ret = k->exit_code;
+
+ put_task_struct(k);
+ trace_sched_kthread_stop_ret(ret);
+
+ return ret;
}
EXPORT_SYMBOL(kthread_stop);
+int kthreadd(void *unused)
+{
+ 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_states[N_HIGH_MEMORY]);
+
+ 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;
+}
+
+void __init_kthread_worker(struct kthread_worker *worker,
+ const char *name,
+ struct lock_class_key *key)
+{
+ spin_lock_init(&worker->lock);
+ lockdep_set_class_and_name(&worker->lock, key, name);
+ INIT_LIST_HEAD(&worker->work_list);
+ worker->task = NULL;
+}
+EXPORT_SYMBOL_GPL(__init_kthread_worker);
+
/**
- * kthread_stop_sem - stop a thread created by kthread_create().
- * @k: thread created by kthread_create().
- * @s: semaphore that @k waits on while idle.
+ * kthread_worker_fn - kthread function to process kthread_worker
+ * @worker_ptr: pointer to initialized kthread_worker
*
- * Does essentially the same thing as kthread_stop() above, but wakes
- * @k by calling up(@s).
+ * This function can be used as @threadfn to kthread_create() or
+ * kthread_run() with @worker_ptr argument pointing to an initialized
+ * kthread_worker. The started kthread will process work_list until
+ * the it is stopped with kthread_stop(). A kthread can also call
+ * this function directly after extra initialization.
*
- * Returns the result of threadfn(), or %-EINTR if wake_up_process()
- * was never called.
+ * Different kthreads can be used for the same kthread_worker as long
+ * as there's only one kthread attached to it at any given time. A
+ * kthread_worker without an attached kthread simply collects queued
+ * kthread_works.
*/
-int kthread_stop_sem(struct task_struct *k, struct semaphore *s)
+int kthread_worker_fn(void *worker_ptr)
{
- int ret;
+ struct kthread_worker *worker = worker_ptr;
+ struct kthread_work *work;
- mutex_lock(&kthread_stop_lock);
-
- /* It could exit after stop_info.k set, but before wake_up_process. */
- get_task_struct(k);
+ WARN_ON(worker->task);
+ worker->task = current;
+repeat:
+ set_current_state(TASK_INTERRUPTIBLE); /* mb paired w/ kthread_stop */
- /* 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);
+ if (kthread_should_stop()) {
+ __set_current_state(TASK_RUNNING);
+ spin_lock_irq(&worker->lock);
+ worker->task = NULL;
+ spin_unlock_irq(&worker->lock);
+ return 0;
+ }
- /* 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);
+ work = NULL;
+ spin_lock_irq(&worker->lock);
+ if (!list_empty(&worker->work_list)) {
+ work = list_first_entry(&worker->work_list,
+ struct kthread_work, node);
+ list_del_init(&work->node);
+ }
+ spin_unlock_irq(&worker->lock);
+
+ if (work) {
+ __set_current_state(TASK_RUNNING);
+ work->func(work);
+ smp_wmb(); /* wmb worker-b0 paired with flush-b1 */
+ work->done_seq = work->queue_seq;
+ smp_mb(); /* mb worker-b1 paired with flush-b0 */
+ if (atomic_read(&work->flushing))
+ wake_up_all(&work->done);
+ } else if (!freezing(current))
+ schedule();
+
+ try_to_freeze();
+ goto repeat;
+}
+EXPORT_SYMBOL_GPL(kthread_worker_fn);
+/**
+ * queue_kthread_work - queue a kthread_work
+ * @worker: target kthread_worker
+ * @work: kthread_work to queue
+ *
+ * Queue @work to work processor @task for async execution. @task
+ * must have been created with kthread_worker_create(). Returns %true
+ * if @work was successfully queued, %false if it was already pending.
+ */
+bool queue_kthread_work(struct kthread_worker *worker,
+ struct kthread_work *work)
+{
+ bool ret = false;
+ unsigned long flags;
+
+ spin_lock_irqsave(&worker->lock, flags);
+ if (list_empty(&work->node)) {
+ list_add_tail(&work->node, &worker->work_list);
+ work->queue_seq++;
+ if (likely(worker->task))
+ wake_up_process(worker->task);
+ ret = true;
+ }
+ spin_unlock_irqrestore(&worker->lock, flags);
return ret;
}
-EXPORT_SYMBOL(kthread_stop_sem);
+EXPORT_SYMBOL_GPL(queue_kthread_work);
-static __init int helper_init(void)
+/**
+ * flush_kthread_work - flush a kthread_work
+ * @work: work to flush
+ *
+ * If @work is queued or executing, wait for it to finish execution.
+ */
+void flush_kthread_work(struct kthread_work *work)
{
- helper_wq = create_singlethread_workqueue("kthread");
- BUG_ON(!helper_wq);
+ int seq = work->queue_seq;
- return 0;
+ atomic_inc(&work->flushing);
+
+ /*
+ * mb flush-b0 paired with worker-b1, to make sure either
+ * worker sees the above increment or we see done_seq update.
+ */
+ smp_mb__after_atomic_inc();
+
+ /* A - B <= 0 tests whether B is in front of A regardless of overflow */
+ wait_event(work->done, seq - work->done_seq <= 0);
+ atomic_dec(&work->flushing);
+
+ /*
+ * rmb flush-b1 paired with worker-b0, to make sure our caller
+ * sees every change made by work->func().
+ */
+ smp_mb__after_atomic_dec();
+}
+EXPORT_SYMBOL_GPL(flush_kthread_work);
+
+struct kthread_flush_work {
+ struct kthread_work work;
+ struct completion done;
+};
+
+static void kthread_flush_work_fn(struct kthread_work *work)
+{
+ struct kthread_flush_work *fwork =
+ container_of(work, struct kthread_flush_work, work);
+ complete(&fwork->done);
}
-core_initcall(helper_init);
+/**
+ * flush_kthread_worker - flush all current works on a kthread_worker
+ * @worker: worker to flush
+ *
+ * Wait until all currently executing or pending works on @worker are
+ * finished.
+ */
+void flush_kthread_worker(struct kthread_worker *worker)
+{
+ struct kthread_flush_work fwork = {
+ KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
+ COMPLETION_INITIALIZER_ONSTACK(fwork.done),
+ };
+
+ queue_kthread_work(worker, &fwork.work);
+ wait_for_completion(&fwork.done);
+}
+EXPORT_SYMBOL_GPL(flush_kthread_worker);
Code Review / linux-2.6.git / blobdiff