include/linux/slow-work.h

   1 /* Worker thread pool for slow items, such as filesystem lookups or mkdirs
   2  *
   3  * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public Licence
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the Licence, or (at your option) any later version.
  10  *
  11  * See Documentation/slow-work.txt
  12  */
  13
  14 #ifndef _LINUX_SLOW_WORK_H
  15 #define _LINUX_SLOW_WORK_H
  16
  17 #ifdef CONFIG_SLOW_WORK
  18
  19 #include <linux/sysctl.h>
  20 #include <linux/timer.h>
  21
  22 struct slow_work;
  23 #ifdef CONFIG_SLOW_WORK_DEBUG
  24 struct seq_file;
  25 #endif
  26
  27 /*
  28  * The operations used to support slow work items
  29  */
  30 struct slow_work_ops {
  31         /* owner */
  32         struct module *owner;
  33
  34         /* get a ref on a work item
  35          * - return 0 if successful, -ve if not
  36          */
  37         int (*get_ref)(struct slow_work *work);
  38
  39         /* discard a ref to a work item */
  40         void (*put_ref)(struct slow_work *work);
  41
  42         /* execute a work item */
  43         void (*execute)(struct slow_work *work);
  44
  45 #ifdef CONFIG_SLOW_WORK_DEBUG
  46         /* describe a work item for debugfs */
  47         void (*desc)(struct slow_work *work, struct seq_file *m);
  48 #endif
  49 };
  50
  51 /*
  52  * A slow work item
  53  * - A reference is held on the parent object by the thread pool when it is
  54  *   queued
  55  */
  56 struct slow_work {
  57         struct module           *owner; /* the owning module */
  58         unsigned long           flags;
  59 #define SLOW_WORK_PENDING       0       /* item pending (further) execution */
  60 #define SLOW_WORK_EXECUTING     1       /* item currently executing */
  61 #define SLOW_WORK_ENQ_DEFERRED  2       /* item enqueue deferred */
  62 #define SLOW_WORK_VERY_SLOW     3       /* item is very slow */
  63 #define SLOW_WORK_CANCELLING    4       /* item is being cancelled, don't enqueue */
  64 #define SLOW_WORK_DELAYED       5       /* item is struct delayed_slow_work with active timer */
  65         const struct slow_work_ops *ops; /* operations table for this item */
  66         struct list_head        link;   /* link in queue */
  67 #ifdef CONFIG_SLOW_WORK_DEBUG
  68         struct timespec         mark;   /* jiffies at which queued or exec begun */
  69 #endif
  70 };
  71
  72 struct delayed_slow_work {
  73         struct slow_work        work;
  74         struct timer_list       timer;
  75 };
  76
  77 /**
  78  * slow_work_init - Initialise a slow work item
  79  * @work: The work item to initialise
  80  * @ops: The operations to use to handle the slow work item
  81  *
  82  * Initialise a slow work item.
  83  */
  84 static inline void slow_work_init(struct slow_work *work,
  85                                   const struct slow_work_ops *ops)
  86 {
  87         work->flags = 0;
  88         work->ops = ops;
  89         INIT_LIST_HEAD(&work->link);
  90 }
  91
  92 /**
  93  * slow_work_init - Initialise a delayed slow work item
  94  * @work: The work item to initialise
  95  * @ops: The operations to use to handle the slow work item
  96  *
  97  * Initialise a delayed slow work item.
  98  */
  99 static inline void delayed_slow_work_init(struct delayed_slow_work *dwork,
 100                                           const struct slow_work_ops *ops)
 101 {
 102         init_timer(&dwork->timer);
 103         slow_work_init(&dwork->work, ops);
 104 }
 105
 106 /**
 107  * vslow_work_init - Initialise a very slow work item
 108  * @work: The work item to initialise
 109  * @ops: The operations to use to handle the slow work item
 110  *
 111  * Initialise a very slow work item.  This item will be restricted such that
 112  * only a certain number of the pool threads will be able to execute items of
 113  * this type.
 114  */
 115 static inline void vslow_work_init(struct slow_work *work,
 116                                    const struct slow_work_ops *ops)
 117 {
 118         work->flags = 1 << SLOW_WORK_VERY_SLOW;
 119         work->ops = ops;
 120         INIT_LIST_HEAD(&work->link);
 121 }
 122
 123 /**
 124  * slow_work_is_queued - Determine if a slow work item is on the work queue
 125  * work: The work item to test
 126  *
 127  * Determine if the specified slow-work item is on the work queue.  This
 128  * returns true if it is actually on the queue.
 129  *
 130  * If the item is executing and has been marked for requeue when execution
 131  * finishes, then false will be returned.
 132  *
 133  * Anyone wishing to wait for completion of execution can wait on the
 134  * SLOW_WORK_EXECUTING bit.
 135  */
 136 static inline bool slow_work_is_queued(struct slow_work *work)
 137 {
 138         unsigned long flags = work->flags;
 139         return flags & SLOW_WORK_PENDING && !(flags & SLOW_WORK_EXECUTING);
 140 }
 141
 142 extern int slow_work_enqueue(struct slow_work *work);
 143 extern void slow_work_cancel(struct slow_work *work);
 144 extern int slow_work_register_user(struct module *owner);
 145 extern void slow_work_unregister_user(struct module *owner);
 146
 147 extern int delayed_slow_work_enqueue(struct delayed_slow_work *dwork,
 148                                      unsigned long delay);
 149
 150 static inline void delayed_slow_work_cancel(struct delayed_slow_work *dwork)
 151 {
 152         slow_work_cancel(&dwork->work);
 153 }
 154
 155 extern bool slow_work_sleep_till_thread_needed(struct slow_work *work,
 156                                                signed long *_timeout);
 157
 158 #ifdef CONFIG_SYSCTL
 159 extern ctl_table slow_work_sysctls[];
 160 #endif
 161
 162 #endif /* CONFIG_SLOW_WORK */
 163 #endif /* _LINUX_SLOW_WORK_H */