2 * Copyright (c) 2008, 2010, Oracle and/or its affiliates. All rights reserved.
3 * Use is subject to license terms.
5 * Author: Nikita Danilov <nikita.danilov@sun.com>
7 * This file is part of Lustre, http://www.lustre.org.
9 * Lustre is free software; you can redistribute it and/or
10 * modify it under the terms of version 2 of the GNU General Public
11 * License as published by the Free Software Foundation.
13 * Lustre is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 * GNU General Public License for more details.
18 * You should have received a copy of the GNU General Public License
19 * along with Lustre; if not, write to the Free Software
20 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
24 #ifndef __LUSTRE_LU_REF_H
25 #define __LUSTRE_LU_REF_H
27 #include <libcfs/list.h>
29 /** \defgroup lu_ref lu_ref
31 * An interface to track references between objects. Mostly for debugging.
33 * Suppose there is a reference counted data-structure struct foo. To track
34 * who acquired references to instance of struct foo, add lu_ref field to it:
38 * atomic_t foo_refcount;
39 * struct lu_ref foo_reference;
44 * foo::foo_reference has to be initialized by calling
45 * lu_ref_init(). Typically there will be functions or macros to increment and
46 * decrement foo::foo_refcount, let's say they are foo_get(struct foo *foo)
47 * and foo_put(struct foo *foo), respectively.
49 * Whenever foo_get() is called to acquire a reference on a foo, lu_ref_add()
50 * has to be called to insert into foo::foo_reference a record, describing
51 * acquired reference. Dually, lu_ref_del() removes matching record. Typical
57 * // bar owns a reference to foo.
58 * bar->bar_foo = foo_get(foo);
59 * lu_ref_add(&foo->foo_reference, "bar", bar);
63 * // reference from bar to foo is released.
64 * lu_ref_del(&foo->foo_reference, "bar", bar);
65 * foo_put(bar->bar_foo);
68 * // current thread acquired a temporary reference to foo.
70 * lu_ref_add(&foo->reference, __FUNCTION__, cfs_current());
74 * // temporary reference is released.
75 * lu_ref_del(&foo->reference, __FUNCTION__, cfs_current());
79 * \e Et \e cetera. Often it makes sense to include lu_ref_add() and
80 * lu_ref_del() calls into foo_get() and foo_put(). When an instance of struct
81 * foo is destroyed, lu_ref_fini() has to be called that checks that no
82 * pending references remain. lu_ref_print() can be used to dump a list of
83 * pending references, while hunting down a leak.
85 * For objects to which a large number of references can be acquired,
86 * lu_ref_del() can become cpu consuming, as it has to scan the list of
87 * references. To work around this, remember result of lu_ref_add() (usually
88 * in the same place where pointer to struct foo is stored), and use
92 * // There is a large number of bar's for a single foo.
93 * bar->bar_foo = foo_get(foo);
94 * bar->bar_foo_ref = lu_ref_add(&foo->foo_reference, "bar", bar);
98 * // reference from bar to foo is released.
99 * lu_ref_del_at(&foo->foo_reference, bar->bar_foo_ref, "bar", bar);
100 * foo_put(bar->bar_foo);
103 * lu_ref interface degrades gracefully in case of memory shortages.
110 /* An incomplete type (defined locally in lu_ref.c) */
114 * Data-structure to keep track of references to a given object. This is used
117 * lu_ref is embedded into an object which other entities (objects, threads,
122 * Spin-lock protecting lu_ref::lf_list.
126 * List of all outstanding references (each represented by struct
127 * lu_ref_link), pointing to this object.
135 * Flag set when lu_ref_add() failed to allocate lu_ref_link. It is
136 * used to mask spurious failure of the following lu_ref_del().
140 * flags - attribute for the lu_ref, for pad and future use.
144 * Where was I initialized?
149 * Linkage into a global list of all lu_ref's (lu_ref_refs).
151 cfs_list_t lf_linkage;
154 void lu_ref_init_loc(struct lu_ref *ref, const char *func, const int line);
155 void lu_ref_fini (struct lu_ref *ref);
156 #define lu_ref_init(ref) lu_ref_init_loc(ref, __FUNCTION__, __LINE__)
158 struct lu_ref_link *lu_ref_add (struct lu_ref *ref, const char *scope,
160 struct lu_ref_link *lu_ref_add_atomic(struct lu_ref *ref, const char *scope,
162 void lu_ref_del (struct lu_ref *ref, const char *scope,
164 void lu_ref_set_at (struct lu_ref *ref,
165 struct lu_ref_link *link,
166 const char *scope, const void *source0,
167 const void *source1);
168 void lu_ref_del_at (struct lu_ref *ref,
169 struct lu_ref_link *link,
170 const char *scope, const void *source);
171 void lu_ref_print (const struct lu_ref *ref);
172 void lu_ref_print_all (void);
174 #else /* !USE_LU_REF */
178 static inline void lu_ref_init(struct lu_ref *ref)
182 static inline void lu_ref_fini(struct lu_ref *ref)
186 static inline struct lu_ref_link *lu_ref_add(struct lu_ref *ref,
193 static inline struct lu_ref_link *lu_ref_add_atomic(struct lu_ref *ref,
200 static inline void lu_ref_del(struct lu_ref *ref, const char *scope,
205 static inline void lu_ref_set_at(struct lu_ref *ref, struct lu_ref_link *link,
206 const char *scope, const void *source0,
211 static inline void lu_ref_del_at(struct lu_ref *ref, struct lu_ref_link *link,
212 const char *scope, const void *source)
216 static inline int lu_ref_global_init(void)
221 static inline void lu_ref_global_fini(void)
225 static inline void lu_ref_print(const struct lu_ref *ref)
229 static inline void lu_ref_print_all(void)
232 #endif /* USE_LU_REF */
236 #endif /* __LUSTRE_LU_REF_H */