1 /* BLURB lgpl
2 
3                            Coda File System
4                               Release 5
5 
6           Copyright (c) 1987-1999 Carnegie Mellon University
7                   Additional copyrights listed below
8 
9 This  code  is  distributed "AS IS" without warranty of any kind under
10 the  terms of the  GNU  Library General Public Licence  Version 2,  as
11 shown in the file LICENSE. The technical and financial contributors to
12 Coda are listed in the file CREDITS.
13 
14                         Additional copyrights
15 
16 #*/
17 
18 /*
19                          IBM COPYRIGHT NOTICE
20 
21                           Copyright (C) 1986
22              International Business Machines Corporation
23                          All Rights Reserved
24 
25 This  file  contains  some  code identical to or derived from the 1986
26 version of the Andrew File System ("AFS"), which is owned by  the  IBM
27 Corporation.   This  code is provided "AS IS" and IBM does not warrant
28 that it is free of infringement of  any  intellectual  rights  of  any
29 third  party.    IBM  disclaims  liability of any kind for any damages
30 whatsoever resulting directly or indirectly from use of this  software
31 or  of  any  derivative work.  Carnegie Mellon University has obtained
32 permission to  modify,  distribute and sublicense this code,  which is
33 based on Version 2  of  AFS  and  does  not  contain  the features and
34 enhancements that are part of  Version 3 of  AFS.  Version 3 of AFS is
35 commercially   available   and  supported  by   Transarc  Corporation,
36 Pittsburgh, PA.
37 
38 */
39 
40 #ifndef _LWP_LOCK_H_
41 #define _LWP_LOCK_H_
42 
43 #ifdef __cplusplus
44 extern "C" {
45 #endif
46 
47 #include <lwp/lwp.h>
48 
49 #define READ_LOCK	1
50 #define WRITE_LOCK	2
51 #define SHARED_LOCK	4
52 
53 /* When compiling for pthreads, always compile with -D_REENTRANT (on glibc
54  * systems) or -D_THREAD_SAFE and -pthread/-kthread (on FreeBSD) */
55 #if !defined(_REENTRANT) && !defined(_THREAD_SAFE)
56 
57 /* all locks wait on excl_locked except for READ_LOCK, which waits on
58  * readers_reading */
59 struct Lock {
60 	unsigned char   wait_states;	/* type of lockers waiting */
61 	unsigned char   excl_locked;	/* anyone have boosted, shared or write lock? */
62 	unsigned char   readers_reading;/* # readers actually with read locks */
63 	unsigned char   num_waiting;	/* probably need this soon */
64 	PROCESS         excl_locker;
65 };
66 
67 /* next defines wait_states for which we wait on excl_locked */
68 #define EXCL_LOCKS (WRITE_LOCK|SHARED_LOCK)
69 
70 void Lock_Obtain (struct Lock*, int);
71 void Lock_ReleaseR (struct Lock *);
72 void Lock_ReleaseW (struct Lock *);
73 
74 #else /* _REENTRANT || _THREAD_SAFE */
75 #include <pthread.h>
76 
77 struct Lock {
78     char             initialized;
79     char             readers;
80     PROCESS          excl;
81     pthread_mutex_t  _access;
82     pthread_cond_t   wakeup;
83 };
84 #endif /* _REENTRANT || _THREAD_SAFE */
85 
86 typedef struct Lock Lock;
87 
88 /* extern definitions for lock manager routines */
89 void ObtainReadLock(struct Lock *lock);
90 void ObtainWriteLock(struct Lock *lock);
91 void ObtainSharedLock(struct Lock *lock);
92 void ReleaseReadLock(struct Lock *lock);
93 void ReleaseWriteLock(struct Lock *lock);
94 void ReleaseSharedLock(struct Lock *lock);
95 int CheckLock(struct Lock *lock);
96 int WriteLocked(struct Lock *lock);
97 void Lock_Init (struct Lock *lock);
98 
99 #ifdef __cplusplus
100 }
101 #endif
102 
103 #endif /* _LWP_LOCK_H_ */
104 
105