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07fe7cb7c7
Create a dynamically sized pool of threads for doing very slow work items, such as invoking mkdir() or rmdir() - things that may take a long time and may sleep, holding mutexes/semaphores and hogging a thread, and are thus unsuitable for workqueues. The number of threads is always at least a settable minimum, but more are started when there's more work to do, up to a limit. Because of the nature of the load, it's not suitable for a 1-thread-per-CPU type pool. A system with one CPU may well want several threads. This is used by FS-Cache to do slow caching operations in the background, such as looking up, creating or deleting cache objects. Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Serge Hallyn <serue@us.ibm.com> Acked-by: Steve Dickson <steved@redhat.com> Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Tested-by: Daire Byrne <Daire.Byrne@framestore.com>
88 lines
2.4 KiB
C
88 lines
2.4 KiB
C
/* Worker thread pool for slow items, such as filesystem lookups or mkdirs
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*
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* Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public Licence
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* as published by the Free Software Foundation; either version
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* 2 of the Licence, or (at your option) any later version.
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*/
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#ifndef _LINUX_SLOW_WORK_H
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#define _LINUX_SLOW_WORK_H
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#ifdef CONFIG_SLOW_WORK
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struct slow_work;
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/*
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* The operations used to support slow work items
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*/
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struct slow_work_ops {
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/* get a ref on a work item
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* - return 0 if successful, -ve if not
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*/
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int (*get_ref)(struct slow_work *work);
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/* discard a ref to a work item */
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void (*put_ref)(struct slow_work *work);
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/* execute a work item */
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void (*execute)(struct slow_work *work);
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};
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/*
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* A slow work item
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* - A reference is held on the parent object by the thread pool when it is
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* queued
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*/
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struct slow_work {
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unsigned long flags;
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#define SLOW_WORK_PENDING 0 /* item pending (further) execution */
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#define SLOW_WORK_EXECUTING 1 /* item currently executing */
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#define SLOW_WORK_ENQ_DEFERRED 2 /* item enqueue deferred */
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#define SLOW_WORK_VERY_SLOW 3 /* item is very slow */
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const struct slow_work_ops *ops; /* operations table for this item */
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struct list_head link; /* link in queue */
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};
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/**
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* slow_work_init - Initialise a slow work item
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* @work: The work item to initialise
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* @ops: The operations to use to handle the slow work item
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*
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* Initialise a slow work item.
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*/
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static inline void slow_work_init(struct slow_work *work,
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const struct slow_work_ops *ops)
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{
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work->flags = 0;
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work->ops = ops;
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INIT_LIST_HEAD(&work->link);
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}
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/**
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* slow_work_init - Initialise a very slow work item
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* @work: The work item to initialise
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* @ops: The operations to use to handle the slow work item
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*
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* Initialise a very slow work item. This item will be restricted such that
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* only a certain number of the pool threads will be able to execute items of
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* this type.
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*/
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static inline void vslow_work_init(struct slow_work *work,
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const struct slow_work_ops *ops)
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{
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work->flags = 1 << SLOW_WORK_VERY_SLOW;
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work->ops = ops;
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INIT_LIST_HEAD(&work->link);
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}
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extern int slow_work_enqueue(struct slow_work *work);
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extern int slow_work_register_user(void);
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extern void slow_work_unregister_user(void);
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#endif /* CONFIG_SLOW_WORK */
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#endif /* _LINUX_SLOW_WORK_H */
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