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![James Bottomley](/assets/img/avatar_default.png)
We have several points in the SCSI stack (primarily for our device functions) where we need to guarantee process context, but (given the place where the last reference was released) we cannot guarantee this. This API gets around the issue by executing the function directly if the caller has process context, but scheduling a workqueue to execute in process context if the caller doesn't have it. Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>
617 lines
15 KiB
C
617 lines
15 KiB
C
/*
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* linux/kernel/workqueue.c
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*
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* Generic mechanism for defining kernel helper threads for running
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* arbitrary tasks in process context.
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*
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* Started by Ingo Molnar, Copyright (C) 2002
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*
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* Derived from the taskqueue/keventd code by:
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*
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* David Woodhouse <dwmw2@infradead.org>
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* Andrew Morton <andrewm@uow.edu.au>
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* Kai Petzke <wpp@marie.physik.tu-berlin.de>
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* Theodore Ts'o <tytso@mit.edu>
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*
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* Made to use alloc_percpu by Christoph Lameter <clameter@sgi.com>.
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*/
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#include <linux/module.h>
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#include <linux/kernel.h>
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#include <linux/sched.h>
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#include <linux/init.h>
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#include <linux/signal.h>
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#include <linux/completion.h>
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#include <linux/workqueue.h>
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#include <linux/slab.h>
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#include <linux/cpu.h>
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#include <linux/notifier.h>
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#include <linux/kthread.h>
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#include <linux/hardirq.h>
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/*
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* The per-CPU workqueue (if single thread, we always use the first
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* possible cpu).
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*
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* The sequence counters are for flush_scheduled_work(). It wants to wait
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* until until all currently-scheduled works are completed, but it doesn't
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* want to be livelocked by new, incoming ones. So it waits until
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* remove_sequence is >= the insert_sequence which pertained when
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* flush_scheduled_work() was called.
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*/
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struct cpu_workqueue_struct {
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spinlock_t lock;
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long remove_sequence; /* Least-recently added (next to run) */
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long insert_sequence; /* Next to add */
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struct list_head worklist;
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wait_queue_head_t more_work;
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wait_queue_head_t work_done;
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struct workqueue_struct *wq;
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task_t *thread;
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int run_depth; /* Detect run_workqueue() recursion depth */
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} ____cacheline_aligned;
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/*
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* The externally visible workqueue abstraction is an array of
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* per-CPU workqueues:
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*/
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struct workqueue_struct {
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struct cpu_workqueue_struct *cpu_wq;
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const char *name;
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struct list_head list; /* Empty if single thread */
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};
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/* All the per-cpu workqueues on the system, for hotplug cpu to add/remove
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threads to each one as cpus come/go. */
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static DEFINE_SPINLOCK(workqueue_lock);
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static LIST_HEAD(workqueues);
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static int singlethread_cpu;
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/* If it's single threaded, it isn't in the list of workqueues. */
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static inline int is_single_threaded(struct workqueue_struct *wq)
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{
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return list_empty(&wq->list);
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}
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/* Preempt must be disabled. */
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static void __queue_work(struct cpu_workqueue_struct *cwq,
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struct work_struct *work)
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{
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unsigned long flags;
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spin_lock_irqsave(&cwq->lock, flags);
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work->wq_data = cwq;
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list_add_tail(&work->entry, &cwq->worklist);
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cwq->insert_sequence++;
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wake_up(&cwq->more_work);
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spin_unlock_irqrestore(&cwq->lock, flags);
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}
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/*
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* Queue work on a workqueue. Return non-zero if it was successfully
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* added.
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*
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* We queue the work to the CPU it was submitted, but there is no
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* guarantee that it will be processed by that CPU.
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*/
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int fastcall queue_work(struct workqueue_struct *wq, struct work_struct *work)
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{
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int ret = 0, cpu = get_cpu();
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if (!test_and_set_bit(0, &work->pending)) {
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if (unlikely(is_single_threaded(wq)))
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cpu = singlethread_cpu;
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BUG_ON(!list_empty(&work->entry));
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__queue_work(per_cpu_ptr(wq->cpu_wq, cpu), work);
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ret = 1;
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}
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put_cpu();
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return ret;
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}
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static void delayed_work_timer_fn(unsigned long __data)
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{
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struct work_struct *work = (struct work_struct *)__data;
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struct workqueue_struct *wq = work->wq_data;
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int cpu = smp_processor_id();
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if (unlikely(is_single_threaded(wq)))
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cpu = singlethread_cpu;
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__queue_work(per_cpu_ptr(wq->cpu_wq, cpu), work);
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}
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int fastcall queue_delayed_work(struct workqueue_struct *wq,
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struct work_struct *work, unsigned long delay)
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{
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int ret = 0;
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struct timer_list *timer = &work->timer;
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if (!test_and_set_bit(0, &work->pending)) {
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BUG_ON(timer_pending(timer));
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BUG_ON(!list_empty(&work->entry));
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/* This stores wq for the moment, for the timer_fn */
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work->wq_data = wq;
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timer->expires = jiffies + delay;
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timer->data = (unsigned long)work;
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timer->function = delayed_work_timer_fn;
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add_timer(timer);
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ret = 1;
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}
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return ret;
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}
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static void run_workqueue(struct cpu_workqueue_struct *cwq)
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{
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unsigned long flags;
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/*
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* Keep taking off work from the queue until
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* done.
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*/
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spin_lock_irqsave(&cwq->lock, flags);
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cwq->run_depth++;
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if (cwq->run_depth > 3) {
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/* morton gets to eat his hat */
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printk("%s: recursion depth exceeded: %d\n",
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__FUNCTION__, cwq->run_depth);
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dump_stack();
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}
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while (!list_empty(&cwq->worklist)) {
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struct work_struct *work = list_entry(cwq->worklist.next,
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struct work_struct, entry);
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void (*f) (void *) = work->func;
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void *data = work->data;
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list_del_init(cwq->worklist.next);
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spin_unlock_irqrestore(&cwq->lock, flags);
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BUG_ON(work->wq_data != cwq);
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clear_bit(0, &work->pending);
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f(data);
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spin_lock_irqsave(&cwq->lock, flags);
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cwq->remove_sequence++;
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wake_up(&cwq->work_done);
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}
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cwq->run_depth--;
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spin_unlock_irqrestore(&cwq->lock, flags);
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}
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static int worker_thread(void *__cwq)
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{
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struct cpu_workqueue_struct *cwq = __cwq;
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DECLARE_WAITQUEUE(wait, current);
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struct k_sigaction sa;
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sigset_t blocked;
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current->flags |= PF_NOFREEZE;
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set_user_nice(current, -5);
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/* Block and flush all signals */
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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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/* SIG_IGN makes children autoreap: see do_notify_parent(). */
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sa.sa.sa_handler = SIG_IGN;
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sa.sa.sa_flags = 0;
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siginitset(&sa.sa.sa_mask, sigmask(SIGCHLD));
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do_sigaction(SIGCHLD, &sa, (struct k_sigaction *)0);
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set_current_state(TASK_INTERRUPTIBLE);
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while (!kthread_should_stop()) {
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add_wait_queue(&cwq->more_work, &wait);
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if (list_empty(&cwq->worklist))
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schedule();
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else
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__set_current_state(TASK_RUNNING);
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remove_wait_queue(&cwq->more_work, &wait);
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if (!list_empty(&cwq->worklist))
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run_workqueue(cwq);
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set_current_state(TASK_INTERRUPTIBLE);
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}
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__set_current_state(TASK_RUNNING);
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return 0;
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}
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static void flush_cpu_workqueue(struct cpu_workqueue_struct *cwq)
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{
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if (cwq->thread == current) {
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/*
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* Probably keventd trying to flush its own queue. So simply run
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* it by hand rather than deadlocking.
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*/
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run_workqueue(cwq);
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} else {
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DEFINE_WAIT(wait);
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long sequence_needed;
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spin_lock_irq(&cwq->lock);
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sequence_needed = cwq->insert_sequence;
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while (sequence_needed - cwq->remove_sequence > 0) {
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prepare_to_wait(&cwq->work_done, &wait,
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TASK_UNINTERRUPTIBLE);
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spin_unlock_irq(&cwq->lock);
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schedule();
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spin_lock_irq(&cwq->lock);
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}
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finish_wait(&cwq->work_done, &wait);
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spin_unlock_irq(&cwq->lock);
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}
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}
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/*
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* flush_workqueue - ensure that any scheduled work has run to completion.
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*
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* Forces execution of the workqueue and blocks until its completion.
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* This is typically used in driver shutdown handlers.
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*
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* This function will sample each workqueue's current insert_sequence number and
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* will sleep until the head sequence is greater than or equal to that. This
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* means that we sleep until all works which were queued on entry have been
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* handled, but we are not livelocked by new incoming ones.
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*
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* This function used to run the workqueues itself. Now we just wait for the
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* helper threads to do it.
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*/
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void fastcall flush_workqueue(struct workqueue_struct *wq)
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{
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might_sleep();
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if (is_single_threaded(wq)) {
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/* Always use first cpu's area. */
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flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, singlethread_cpu));
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} else {
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int cpu;
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lock_cpu_hotplug();
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for_each_online_cpu(cpu)
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flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, cpu));
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unlock_cpu_hotplug();
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}
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}
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static struct task_struct *create_workqueue_thread(struct workqueue_struct *wq,
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int cpu)
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{
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struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);
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struct task_struct *p;
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spin_lock_init(&cwq->lock);
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cwq->wq = wq;
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cwq->thread = NULL;
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cwq->insert_sequence = 0;
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cwq->remove_sequence = 0;
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INIT_LIST_HEAD(&cwq->worklist);
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init_waitqueue_head(&cwq->more_work);
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init_waitqueue_head(&cwq->work_done);
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if (is_single_threaded(wq))
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p = kthread_create(worker_thread, cwq, "%s", wq->name);
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else
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p = kthread_create(worker_thread, cwq, "%s/%d", wq->name, cpu);
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if (IS_ERR(p))
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return NULL;
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cwq->thread = p;
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return p;
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}
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struct workqueue_struct *__create_workqueue(const char *name,
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int singlethread)
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{
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int cpu, destroy = 0;
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struct workqueue_struct *wq;
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struct task_struct *p;
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wq = kzalloc(sizeof(*wq), GFP_KERNEL);
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if (!wq)
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return NULL;
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wq->cpu_wq = alloc_percpu(struct cpu_workqueue_struct);
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if (!wq->cpu_wq) {
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kfree(wq);
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return NULL;
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}
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wq->name = name;
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/* We don't need the distraction of CPUs appearing and vanishing. */
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lock_cpu_hotplug();
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if (singlethread) {
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INIT_LIST_HEAD(&wq->list);
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p = create_workqueue_thread(wq, singlethread_cpu);
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if (!p)
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destroy = 1;
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else
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wake_up_process(p);
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} else {
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spin_lock(&workqueue_lock);
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list_add(&wq->list, &workqueues);
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spin_unlock(&workqueue_lock);
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for_each_online_cpu(cpu) {
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p = create_workqueue_thread(wq, cpu);
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if (p) {
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kthread_bind(p, cpu);
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wake_up_process(p);
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} else
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destroy = 1;
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}
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}
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unlock_cpu_hotplug();
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/*
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* Was there any error during startup? If yes then clean up:
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*/
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if (destroy) {
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destroy_workqueue(wq);
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wq = NULL;
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}
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return wq;
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}
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static void cleanup_workqueue_thread(struct workqueue_struct *wq, int cpu)
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{
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struct cpu_workqueue_struct *cwq;
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unsigned long flags;
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struct task_struct *p;
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cwq = per_cpu_ptr(wq->cpu_wq, cpu);
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spin_lock_irqsave(&cwq->lock, flags);
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p = cwq->thread;
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cwq->thread = NULL;
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spin_unlock_irqrestore(&cwq->lock, flags);
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if (p)
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kthread_stop(p);
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}
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void destroy_workqueue(struct workqueue_struct *wq)
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{
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int cpu;
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flush_workqueue(wq);
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/* We don't need the distraction of CPUs appearing and vanishing. */
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lock_cpu_hotplug();
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if (is_single_threaded(wq))
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cleanup_workqueue_thread(wq, singlethread_cpu);
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else {
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for_each_online_cpu(cpu)
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cleanup_workqueue_thread(wq, cpu);
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spin_lock(&workqueue_lock);
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list_del(&wq->list);
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spin_unlock(&workqueue_lock);
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}
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unlock_cpu_hotplug();
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free_percpu(wq->cpu_wq);
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kfree(wq);
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}
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static struct workqueue_struct *keventd_wq;
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int fastcall schedule_work(struct work_struct *work)
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{
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return queue_work(keventd_wq, work);
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}
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int fastcall schedule_delayed_work(struct work_struct *work, unsigned long delay)
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{
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return queue_delayed_work(keventd_wq, work, delay);
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}
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int schedule_delayed_work_on(int cpu,
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struct work_struct *work, unsigned long delay)
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{
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int ret = 0;
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struct timer_list *timer = &work->timer;
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if (!test_and_set_bit(0, &work->pending)) {
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BUG_ON(timer_pending(timer));
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BUG_ON(!list_empty(&work->entry));
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/* This stores keventd_wq for the moment, for the timer_fn */
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work->wq_data = keventd_wq;
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timer->expires = jiffies + delay;
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timer->data = (unsigned long)work;
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timer->function = delayed_work_timer_fn;
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add_timer_on(timer, cpu);
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ret = 1;
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}
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return ret;
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}
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int schedule_on_each_cpu(void (*func) (void *info), void *info)
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{
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int cpu;
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struct work_struct *work;
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work = kmalloc(NR_CPUS * sizeof(struct work_struct), GFP_KERNEL);
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if (!work)
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return -ENOMEM;
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for_each_online_cpu(cpu) {
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INIT_WORK(work + cpu, func, info);
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__queue_work(per_cpu_ptr(keventd_wq->cpu_wq, cpu),
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work + cpu);
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}
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flush_workqueue(keventd_wq);
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kfree(work);
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return 0;
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}
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void flush_scheduled_work(void)
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{
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flush_workqueue(keventd_wq);
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}
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/**
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* cancel_rearming_delayed_workqueue - reliably kill off a delayed
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* work whose handler rearms the delayed work.
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* @wq: the controlling workqueue structure
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* @work: the delayed work struct
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*/
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void cancel_rearming_delayed_workqueue(struct workqueue_struct *wq,
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struct work_struct *work)
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{
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while (!cancel_delayed_work(work))
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flush_workqueue(wq);
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}
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EXPORT_SYMBOL(cancel_rearming_delayed_workqueue);
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/**
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* cancel_rearming_delayed_work - reliably kill off a delayed keventd
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* work whose handler rearms the delayed work.
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* @work: the delayed work struct
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*/
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void cancel_rearming_delayed_work(struct work_struct *work)
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{
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cancel_rearming_delayed_workqueue(keventd_wq, work);
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}
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EXPORT_SYMBOL(cancel_rearming_delayed_work);
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/**
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* execute_in_process_context - reliably execute the routine with user context
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* @fn: the function to execute
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* @data: data to pass to the function
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* @ew: guaranteed storage for the execute work structure (must
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* be available when the work executes)
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*
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* Executes the function immediately if process context is available,
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* otherwise schedules the function for delayed execution.
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*
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* Returns: 0 - function was executed
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* 1 - function was scheduled for execution
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*/
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int execute_in_process_context(void (*fn)(void *data), void *data,
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struct execute_work *ew)
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{
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if (!in_interrupt()) {
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fn(data);
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return 0;
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}
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INIT_WORK(&ew->work, fn, data);
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schedule_work(&ew->work);
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return 1;
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}
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EXPORT_SYMBOL_GPL(execute_in_process_context);
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int keventd_up(void)
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{
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return keventd_wq != NULL;
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}
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int current_is_keventd(void)
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{
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struct cpu_workqueue_struct *cwq;
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int cpu = smp_processor_id(); /* preempt-safe: keventd is per-cpu */
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int ret = 0;
|
|
|
|
BUG_ON(!keventd_wq);
|
|
|
|
cwq = per_cpu_ptr(keventd_wq->cpu_wq, cpu);
|
|
if (current == cwq->thread)
|
|
ret = 1;
|
|
|
|
return ret;
|
|
|
|
}
|
|
|
|
#ifdef CONFIG_HOTPLUG_CPU
|
|
/* Take the work from this (downed) CPU. */
|
|
static void take_over_work(struct workqueue_struct *wq, unsigned int cpu)
|
|
{
|
|
struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);
|
|
LIST_HEAD(list);
|
|
struct work_struct *work;
|
|
|
|
spin_lock_irq(&cwq->lock);
|
|
list_splice_init(&cwq->worklist, &list);
|
|
|
|
while (!list_empty(&list)) {
|
|
printk("Taking work for %s\n", wq->name);
|
|
work = list_entry(list.next,struct work_struct,entry);
|
|
list_del(&work->entry);
|
|
__queue_work(per_cpu_ptr(wq->cpu_wq, smp_processor_id()), work);
|
|
}
|
|
spin_unlock_irq(&cwq->lock);
|
|
}
|
|
|
|
/* We're holding the cpucontrol mutex here */
|
|
static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
|
|
unsigned long action,
|
|
void *hcpu)
|
|
{
|
|
unsigned int hotcpu = (unsigned long)hcpu;
|
|
struct workqueue_struct *wq;
|
|
|
|
switch (action) {
|
|
case CPU_UP_PREPARE:
|
|
/* Create a new workqueue thread for it. */
|
|
list_for_each_entry(wq, &workqueues, list) {
|
|
if (!create_workqueue_thread(wq, hotcpu)) {
|
|
printk("workqueue for %i failed\n", hotcpu);
|
|
return NOTIFY_BAD;
|
|
}
|
|
}
|
|
break;
|
|
|
|
case CPU_ONLINE:
|
|
/* Kick off worker threads. */
|
|
list_for_each_entry(wq, &workqueues, list) {
|
|
struct cpu_workqueue_struct *cwq;
|
|
|
|
cwq = per_cpu_ptr(wq->cpu_wq, hotcpu);
|
|
kthread_bind(cwq->thread, hotcpu);
|
|
wake_up_process(cwq->thread);
|
|
}
|
|
break;
|
|
|
|
case CPU_UP_CANCELED:
|
|
list_for_each_entry(wq, &workqueues, list) {
|
|
/* Unbind so it can run. */
|
|
kthread_bind(per_cpu_ptr(wq->cpu_wq, hotcpu)->thread,
|
|
any_online_cpu(cpu_online_map));
|
|
cleanup_workqueue_thread(wq, hotcpu);
|
|
}
|
|
break;
|
|
|
|
case CPU_DEAD:
|
|
list_for_each_entry(wq, &workqueues, list)
|
|
cleanup_workqueue_thread(wq, hotcpu);
|
|
list_for_each_entry(wq, &workqueues, list)
|
|
take_over_work(wq, hotcpu);
|
|
break;
|
|
}
|
|
|
|
return NOTIFY_OK;
|
|
}
|
|
#endif
|
|
|
|
void init_workqueues(void)
|
|
{
|
|
singlethread_cpu = first_cpu(cpu_possible_map);
|
|
hotcpu_notifier(workqueue_cpu_callback, 0);
|
|
keventd_wq = create_workqueue("events");
|
|
BUG_ON(!keventd_wq);
|
|
}
|
|
|
|
EXPORT_SYMBOL_GPL(__create_workqueue);
|
|
EXPORT_SYMBOL_GPL(queue_work);
|
|
EXPORT_SYMBOL_GPL(queue_delayed_work);
|
|
EXPORT_SYMBOL_GPL(flush_workqueue);
|
|
EXPORT_SYMBOL_GPL(destroy_workqueue);
|
|
|
|
EXPORT_SYMBOL(schedule_work);
|
|
EXPORT_SYMBOL(schedule_delayed_work);
|
|
EXPORT_SYMBOL(schedule_delayed_work_on);
|
|
EXPORT_SYMBOL(flush_scheduled_work);
|