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         /* owner */
  28         struct module *owner;
  29
  30         /* get a ref on a work item
  31          * - return 0 if successful, -ve if not
  32          */
  33         int (*get_ref)(struct slow_work *work);
  34
  35         /* discard a ref to a work item */
  36         void (*put_ref)(struct slow_work *work);
  37
  38         /* execute a work item */
  39         void (*execute)(struct slow_work *work);
  40 };
  41
  42 /*
  43  * A slow work item
  44  * - A reference is held on the parent object by the thread pool when it is
  45  *   queued
  46  */
  47 struct slow_work {
  48         struct module           *owner; /* the owning module */
  49         unsigned long           flags;
  50 #define SLOW_WORK_PENDING       0       /* item pending (further) execution */
  51 #define SLOW_WORK_EXECUTING     1       /* item currently executing */
  52 #define SLOW_WORK_ENQ_DEFERRED  2       /* item enqueue deferred */
  53 #define SLOW_WORK_VERY_SLOW     3       /* item is very slow */
  54 #define SLOW_WORK_CANCELLING    4       /* item is being cancelled, don't enqueue */
  55         const struct slow_work_ops *ops; /* operations table for this item */
  56         struct list_head        link;   /* link in queue */
  57 };
  58
  59 /**
  60  * slow_work_init - Initialise a slow work item
  61  * @work: The work item to initialise
  62  * @ops: The operations to use to handle the slow work item
  63  *
  64  * Initialise a slow work item.
  65  */
  66 static inline void slow_work_init(struct slow_work *work,
  67                                   const struct slow_work_ops *ops)
  68 {
  69         work->flags = 0;
  70         work->ops = ops;
  71         INIT_LIST_HEAD(&work->link);
  72 }
  73
  74 /**
  75  * vslow_work_init - Initialise a very slow work item
  76  * @work: The work item to initialise
  77  * @ops: The operations to use to handle the slow work item
  78  *
  79  * Initialise a very slow work item.  This item will be restricted such that
  80  * only a certain number of the pool threads will be able to execute items of
  81  * this type.
  82  */
  83 static inline void vslow_work_init(struct slow_work *work,
  84                                    const struct slow_work_ops *ops)
  85 {
  86         work->flags = 1 << SLOW_WORK_VERY_SLOW;
  87         work->ops = ops;
  88         INIT_LIST_HEAD(&work->link);
  89 }
  90
  91 extern int slow_work_enqueue(struct slow_work *work);
  92 extern void slow_work_cancel(struct slow_work *work);
  93 extern int slow_work_register_user(struct module *owner);
  94 extern void slow_work_unregister_user(struct module *owner);
  95
  96 #ifdef CONFIG_SYSCTL
  97 extern ctl_table slow_work_sysctls[];
  98 #endif
  99
 100 #endif /* CONFIG_SLOW_WORK */
 101 #endif /* _LINUX_SLOW_WORK_H */