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
  21 struct slow_work;
  22
  23 /*
  24  * The operations used to support slow work items
  25  */
  26 struct slow_work_ops {
  27         /* get a ref on a work item
  28          * - return 0 if successful, -ve if not
  29          */
  30         int (*get_ref)(struct slow_work *work);
  31
  32         /* discard a ref to a work item */
  33         void (*put_ref)(struct slow_work *work);
  34
  35         /* execute a work item */
  36         void (*execute)(struct slow_work *work);
  37 };
  38
  39 /*
  40  * A slow work item
  41  * - A reference is held on the parent object by the thread pool when it is
  42  *   queued
  43  */
  44 struct slow_work {
  45         unsigned long           flags;
  46 #define SLOW_WORK_PENDING       0       /* item pending (further) execution */
  47 #define SLOW_WORK_EXECUTING     1       /* item currently executing */
  48 #define SLOW_WORK_ENQ_DEFERRED  2       /* item enqueue deferred */
  49 #define SLOW_WORK_VERY_SLOW     3       /* item is very slow */
  50         const struct slow_work_ops *ops; /* operations table for this item */
  51         struct list_head        link;   /* link in queue */
  52 };
  53
  54 /**
  55  * slow_work_init - Initialise a slow work item
  56  * @work: The work item to initialise
  57  * @ops: The operations to use to handle the slow work item
  58  *
  59  * Initialise a slow work item.
  60  */
  61 static inline void slow_work_init(struct slow_work *work,
  62                                   const struct slow_work_ops *ops)
  63 {
  64         work->flags = 0;
  65         work->ops = ops;
  66         INIT_LIST_HEAD(&work->link);
  67 }
  68
  69 /**
  70  * vslow_work_init - Initialise a very slow work item
  71  * @work: The work item to initialise
  72  * @ops: The operations to use to handle the slow work item
  73  *
  74  * Initialise a very slow work item.  This item will be restricted such that
  75  * only a certain number of the pool threads will be able to execute items of
  76  * this type.
  77  */
  78 static inline void vslow_work_init(struct slow_work *work,
  79                                    const struct slow_work_ops *ops)
  80 {
  81         work->flags = 1 << SLOW_WORK_VERY_SLOW;
  82         work->ops = ops;
  83         INIT_LIST_HEAD(&work->link);
  84 }
  85
  86 extern int slow_work_enqueue(struct slow_work *work);
  87 extern int slow_work_register_user(void);
  88 extern void slow_work_unregister_user(void);
  89
  90 #ifdef CONFIG_SYSCTL
  91 extern ctl_table slow_work_sysctls[];
  92 #endif
  93
  94 #endif /* CONFIG_SLOW_WORK */
  95 #endif /* _LINUX_SLOW_WORK_H */