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1/*
2** 2007 August 28
3**
4** The author disclaims copyright to this source code. In place of
5** a legal notice, here is a blessing:
6**
7** May you do good and not evil.
8** May you find forgiveness for yourself and forgive others.
9** May you share freely, never taking more than you give.
10**
11*************************************************************************
12** This file contains the C functions that implement mutexes for OS/2
13**
14** $Id: mutex_os2.c,v 1.3 2007/10/02 19:56:04 pweilbacher Exp $
15*/
16#include "sqliteInt.h"
17
18/*
19** The code in this file is only used if SQLITE_MUTEX_OS2 is defined.
20** See the mutex.h file for details.
21*/
22#ifdef SQLITE_MUTEX_OS2
23
24/********************** OS/2 Mutex Implementation **********************
25**
26** This implementation of mutexes is built using the OS/2 API.
27*/
28
29/*
30** The mutex object
31** Each recursive mutex is an instance of the following structure.
32*/
33struct sqlite3_mutex {
34 PSZ mutexName; /* Mutex name controlling the lock */
35 HMTX mutex; /* Mutex controlling the lock */
36 int id; /* Mutex type */
37 int nRef; /* Number of references */
38 TID owner; /* Thread holding this mutex */
39};
40
41/*
42** The sqlite3_mutex_alloc() routine allocates a new
43** mutex and returns a pointer to it. If it returns NULL
44** that means that a mutex could not be allocated.
45** SQLite will unwind its stack and return an error. The argument
46** to sqlite3_mutex_alloc() is one of these integer constants:
47**
48** <ul>
49** <li> SQLITE_MUTEX_FAST 0
50** <li> SQLITE_MUTEX_RECURSIVE 1
51** <li> SQLITE_MUTEX_STATIC_MASTER 2
52** <li> SQLITE_MUTEX_STATIC_MEM 3
53** <li> SQLITE_MUTEX_STATIC_PRNG 4
54** </ul>
55**
56** The first two constants cause sqlite3_mutex_alloc() to create
57** a new mutex. The new mutex is recursive when SQLITE_MUTEX_RECURSIVE
58** is used but not necessarily so when SQLITE_MUTEX_FAST is used.
59** The mutex implementation does not need to make a distinction
60** between SQLITE_MUTEX_RECURSIVE and SQLITE_MUTEX_FAST if it does
61** not want to. But SQLite will only request a recursive mutex in
62** cases where it really needs one. If a faster non-recursive mutex
63** implementation is available on the host platform, the mutex subsystem
64** might return such a mutex in response to SQLITE_MUTEX_FAST.
65**
66** The other allowed parameters to sqlite3_mutex_alloc() each return
67** a pointer to a static preexisting mutex. Three static mutexes are
68** used by the current version of SQLite. Future versions of SQLite
69** may add additional static mutexes. Static mutexes are for internal
70** use by SQLite only. Applications that use SQLite mutexes should
71** use only the dynamic mutexes returned by SQLITE_MUTEX_FAST or
72** SQLITE_MUTEX_RECURSIVE.
73**
74** Note that if one of the dynamic mutex parameters (SQLITE_MUTEX_FAST
75** or SQLITE_MUTEX_RECURSIVE) is used then sqlite3_mutex_alloc()
76** returns a different mutex on every call. But for the static
77** mutex types, the same mutex is returned on every call that has
78** the same type number.
79*/
80sqlite3_mutex *sqlite3_mutex_alloc(int iType){
81 PSZ mutex_name = "\\SEM32\\SQLITE\\MUTEX";
82 int mutex_name_len = strlen(mutex_name) + 1; /* name length + null byte */
83 sqlite3_mutex *p;
84
85 switch( iType ){
86 case SQLITE_MUTEX_FAST:
87 case SQLITE_MUTEX_RECURSIVE: {
88 p = sqlite3MallocZero( sizeof(*p) );
89 if( p ){
90 p->mutexName = (PSZ)malloc(mutex_name_len);
91 sqlite3_snprintf(mutex_name_len, p->mutexName, "%s", mutex_name);
92 p->id = iType;
93 DosCreateMutexSem(p->mutexName, &p->mutex, 0, FALSE);
94 DosOpenMutexSem(p->mutexName, &p->mutex);
95 }
96 break;
97 }
98 default: {
99 static sqlite3_mutex staticMutexes[5];
100 static int isInit = 0;
101 while( !isInit ) {
102 static long lock = 0;
103 DosEnterCritSec();
104 lock++;
105 if( lock == 1 ) {
106 DosExitCritSec();
107 int i;
108 for(i = 0; i < sizeof(staticMutexes)/sizeof(staticMutexes[0]); i++) {
109 staticMutexes[i].mutexName = (PSZ)malloc(mutex_name_len + 1);
110 sqlite3_snprintf(mutex_name_len + 1, /* one more for the number */
111 staticMutexes[i].mutexName, "%s%1d", mutex_name, i);
112 DosCreateMutexSem(staticMutexes[i].mutexName,
113 &staticMutexes[i].mutex, 0, FALSE);
114 DosOpenMutexSem(staticMutexes[i].mutexName,
115 &staticMutexes[i].mutex);
116 }
117 isInit = 1;
118 } else {
119 DosExitCritSec();
120 DosSleep(1);
121 }
122 }
123 assert( iType-2 >= 0 );
124 assert( iType-2 < sizeof(staticMutexes)/sizeof(staticMutexes[0]) );
125 p = &staticMutexes[iType-2];
126 p->id = iType;
127 break;
128 }
129 }
130 return p;
131}
132
133
134/*
135** This routine deallocates a previously allocated mutex.
136** SQLite is careful to deallocate every mutex that it allocates.
137*/
138void sqlite3_mutex_free(sqlite3_mutex *p){
139 assert( p );
140 assert( p->nRef==0 );
141 assert( p->id==SQLITE_MUTEX_FAST || p->id==SQLITE_MUTEX_RECURSIVE );
142 DosCloseMutexSem(p->mutex);
143 free(p->mutexName);
144 sqlite3_free(p);
145}
146
147/*
148** The sqlite3_mutex_enter() and sqlite3_mutex_try() routines attempt
149** to enter a mutex. If another thread is already within the mutex,
150** sqlite3_mutex_enter() will block and sqlite3_mutex_try() will return
151** SQLITE_BUSY. The sqlite3_mutex_try() interface returns SQLITE_OK
152** upon successful entry. Mutexes created using SQLITE_MUTEX_RECURSIVE can
153** be entered multiple times by the same thread. In such cases the,
154** mutex must be exited an equal number of times before another thread
155** can enter. If the same thread tries to enter any other kind of mutex
156** more than once, the behavior is undefined.
157*/
158void sqlite3_mutex_enter(sqlite3_mutex *p){
159 TID tid;
160 PID holder1;
161 ULONG holder2;
162 assert( p );
163 assert( p->id==SQLITE_MUTEX_RECURSIVE || sqlite3_mutex_notheld(p) );
164 DosRequestMutexSem(p->mutex, SEM_INDEFINITE_WAIT);
165 DosQueryMutexSem(p->mutex, &holder1, &tid, &holder2);
166 p->owner = tid;
167 p->nRef++;
168}
169int sqlite3_mutex_try(sqlite3_mutex *p){
170 int rc;
171 TID tid;
172 PID holder1;
173 ULONG holder2;
174 assert( p );
175 assert( p->id==SQLITE_MUTEX_RECURSIVE || sqlite3_mutex_notheld(p) );
176 if( DosRequestMutexSem(p->mutex, SEM_IMMEDIATE_RETURN) == NO_ERROR) {
177 DosQueryMutexSem(p->mutex, &holder1, &tid, &holder2);
178 p->owner = tid;
179 p->nRef++;
180 rc = SQLITE_OK;
181 } else {
182 rc = SQLITE_BUSY;
183 }
184
185 return rc;
186}
187
188/*
189** The sqlite3_mutex_leave() routine exits a mutex that was
190** previously entered by the same thread. The behavior
191** is undefined if the mutex is not currently entered or
192** is not currently allocated. SQLite will never do either.
193*/
194void sqlite3_mutex_leave(sqlite3_mutex *p){
195 TID tid;
196 PID holder1;
197 ULONG holder2;
198 assert( p->nRef>0 );
199 DosQueryMutexSem(p->mutex, &holder1, &tid, &holder2);
200 assert( p->owner==tid );
201 p->nRef--;
202 assert( p->nRef==0 || p->id==SQLITE_MUTEX_RECURSIVE );
203 DosReleaseMutexSem(p->mutex);
204}
205
206/*
207** The sqlite3_mutex_held() and sqlite3_mutex_notheld() routine are
208** intended for use inside assert() statements.
209*/
210int sqlite3_mutex_held(sqlite3_mutex *p){
211 TID tid;
212 PID pid;
213 ULONG ulCount;
214 PTIB ptib;
215 if( p!=0 ) {
216 DosQueryMutexSem(p->mutex, &pid, &tid, &ulCount);
217 } else {
218 DosGetInfoBlocks(&ptib, NULL);
219 tid = ptib->tib_ptib2->tib2_ultid;
220 }
221 return p==0 || (p->nRef!=0 && p->owner==tid);
222}
223int sqlite3_mutex_notheld(sqlite3_mutex *p){
224 TID tid;
225 PID pid;
226 ULONG ulCount;
227 PTIB ptib;
228 if( p!= 0 ) {
229 DosQueryMutexSem(p->mutex, &pid, &tid, &ulCount);
230 } else {
231 DosGetInfoBlocks(&ptib, NULL);
232 tid = ptib->tib_ptib2->tib2_ultid;
233 }
234 return p==0 || p->nRef==0 || p->owner!=tid;
235}
236#endif /* SQLITE_MUTEX_OS2 */
generated by cgit v1.1 at 2024-11-11 07:27:37 +0000