1 /*
2 * GPL HEADER START
3 *
4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 only,
8 * as published by the Free Software Foundation.
9 *
10 * This program is distributed in the hope that it will be useful, but
11 * WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * General Public License version 2 for more details (a copy is included
14 * in the LICENSE file that accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License
17 * version 2 along with this program; If not, see
18 * http://www.gnu.org/licenses/gpl-2.0.html
19 *
20 * GPL HEADER END
21 */
22 /*
23 * Copyright (c) 2008, 2010, Oracle and/or its affiliates. All rights reserved.
24 * Use is subject to license terms.
25 *
26 * Copyright (c) 2012, Intel Corporation.
27 */
28 /*
29 * This file is part of Lustre, http://www.lustre.org/
30 * Lustre is a trademark of Sun Microsystems, Inc.
31 *
32 * libcfs/include/libcfs/libcfs_workitem.h
33 *
34 * Author: Isaac Huang <he.h.huang@oracle.com>
35 * Liang Zhen <zhen.liang@sun.com>
36 *
37 * A workitems is deferred work with these semantics:
38 * - a workitem always runs in thread context.
39 * - a workitem can be concurrent with other workitems but is strictly
40 * serialized with respect to itself.
41 * - no CPU affinity, a workitem does not necessarily run on the same CPU
42 * that schedules it. However, this might change in the future.
43 * - if a workitem is scheduled again before it has a chance to run, it
44 * runs only once.
45 * - if a workitem is scheduled while it runs, it runs again after it
46 * completes; this ensures that events occurring while other events are
47 * being processed receive due attention. This behavior also allows a
48 * workitem to reschedule itself.
49 *
50 * Usage notes:
51 * - a workitem can sleep but it should be aware of how that sleep might
52 * affect others.
53 * - a workitem runs inside a kernel thread so there's no user space to access.
54 * - do not use a workitem if the scheduling latency can't be tolerated.
55 *
56 * When wi_action returns non-zero, it means the workitem has either been
57 * freed or reused and workitem scheduler won't touch it any more.
58 */
59
60 #ifndef __LIBCFS_WORKITEM_H__
61 #define __LIBCFS_WORKITEM_H__
62
63 struct cfs_wi_sched;
64
65 void cfs_wi_sched_destroy(struct cfs_wi_sched *);
66 int cfs_wi_sched_create(char *name, struct cfs_cpt_table *cptab, int cpt,
67 int nthrs, struct cfs_wi_sched **);
68
69 struct cfs_workitem;
70
71 typedef int (*cfs_wi_action_t) (struct cfs_workitem *);
72 struct cfs_workitem {
73 /** chain on runq or rerunq */
74 struct list_head wi_list;
75 /** working function */
76 cfs_wi_action_t wi_action;
77 /** arg for working function */
78 void *wi_data;
79 /** in running */
80 unsigned short wi_running:1;
81 /** scheduled */
82 unsigned short wi_scheduled:1;
83 };
84
85 static inline void
cfs_wi_init(struct cfs_workitem * wi,void * data,cfs_wi_action_t action)86 cfs_wi_init(struct cfs_workitem *wi, void *data, cfs_wi_action_t action)
87 {
88 INIT_LIST_HEAD(&wi->wi_list);
89
90 wi->wi_running = 0;
91 wi->wi_scheduled = 0;
92 wi->wi_data = data;
93 wi->wi_action = action;
94 }
95
96 void cfs_wi_schedule(struct cfs_wi_sched *sched, struct cfs_workitem *wi);
97 int cfs_wi_deschedule(struct cfs_wi_sched *sched, struct cfs_workitem *wi);
98 void cfs_wi_exit(struct cfs_wi_sched *sched, struct cfs_workitem *wi);
99
100 int cfs_wi_startup(void);
101 void cfs_wi_shutdown(void);
102
103 /** # workitem scheduler loops before reschedule */
104 #define CFS_WI_RESCHED 128
105
106 #endif /* __LIBCFS_WORKITEM_H__ */
107