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chromium / external / github.com / sqlite / sqlite / HEAD / . / src / mutex_unix.c
blob: beae877f987816f33d37616367727ee57274d18b [file] [log] [blame]
drh437b9012007-08-28 16:34:42[diff] [blame]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 pthreads
drh437b9012007-08-28 16:34:42[diff] [blame]13*/
14#include "sqliteInt.h"
15
16/*
17** The code in this file is only used if we are compiling threadsafe
18** under unix with pthreads.
19**
20** Note that this implementation requires a version of pthreads that
21** supports recursive mutexes.
22*/
23#ifdef SQLITE_MUTEX_PTHREADS
24
25#include <pthread.h>
26
drh72339a32010-05-13 20:19:17[diff] [blame]27/*
28** The sqlite3_mutex.id, sqlite3_mutex.nRef, and sqlite3_mutex.owner fields
larrybrbc917382023-06-07 08:40:31[diff] [blame]29** are necessary under two conditions: (1) Debug builds and (2) using
drh72339a32010-05-13 20:19:17[diff] [blame]30** home-grown mutexes. Encapsulate these conditions into a single #define.
31*/
32#if defined(SQLITE_DEBUG) || defined(SQLITE_HOMEGROWN_RECURSIVE_MUTEX)
33# define SQLITE_MUTEX_NREF 1
34#else
35# define SQLITE_MUTEX_NREF 0
36#endif
drhed05efb2007-11-28 00:51:34[diff] [blame]37
drh437b9012007-08-28 16:34:42[diff] [blame]38/*
39** Each recursive mutex is an instance of the following structure.
40*/
41struct sqlite3_mutex {
42 pthread_mutex_t mutex; /* Mutex controlling the lock */
drh96c707a2015-02-13 16:36:14[diff] [blame]43#if SQLITE_MUTEX_NREF || defined(SQLITE_ENABLE_API_ARMOR)
drh437b9012007-08-28 16:34:42[diff] [blame]44 int id; /* Mutex type */
drh96c707a2015-02-13 16:36:14[diff] [blame]45#endif
46#if SQLITE_MUTEX_NREF
drh72339a32010-05-13 20:19:17[diff] [blame]47 volatile int nRef; /* Number of entrances */
48 volatile pthread_t owner; /* Thread that is within this mutex */
drhd0679ed2007-08-28 22:24:34[diff] [blame]49 int trace; /* True to trace changes */
50#endif
drh437b9012007-08-28 16:34:42[diff] [blame]51};
drh72339a32010-05-13 20:19:17[diff] [blame]52#if SQLITE_MUTEX_NREF
danc5515502018-02-17 07:38:50[diff] [blame]53# define SQLITE3_MUTEX_INITIALIZER(id) \
54 {PTHREAD_MUTEX_INITIALIZER,id,0,(pthread_t)0,0}
dan3e6a1412015-12-23 16:42:27[diff] [blame]55#elif defined(SQLITE_ENABLE_API_ARMOR)
danc5515502018-02-17 07:38:50[diff] [blame]56# define SQLITE3_MUTEX_INITIALIZER(id) { PTHREAD_MUTEX_INITIALIZER, id }
rse28f667f2008-03-29 12:47:27[diff] [blame]57#else
danc5515502018-02-17 07:38:50[diff] [blame]58#define SQLITE3_MUTEX_INITIALIZER(id) { PTHREAD_MUTEX_INITIALIZER }
rse28f667f2008-03-29 12:47:27[diff] [blame]59#endif
drh437b9012007-08-28 16:34:42[diff] [blame]60
61/*
danielk19776d2ab0e2008-06-17 17:21:18[diff] [blame]62** The sqlite3_mutex_held() and sqlite3_mutex_notheld() routine are
63** intended for use only inside assert() statements. On some platforms,
64** there might be race conditions that can cause these routines to
65** deliver incorrect results. In particular, if pthread_equal() is
66** not an atomic operation, then these routines might delivery
larrybrbc917382023-06-07 08:40:31[diff] [blame]67** incorrect results. On most platforms, pthread_equal() is a
danielk19776d2ab0e2008-06-17 17:21:18[diff] [blame]68** comparison of two integers and is therefore atomic. But we are
69** told that HPUX is not such a platform. If so, then these routines
70** will not always work correctly on HPUX.
71**
72** On those platforms where pthread_equal() is not atomic, SQLite
73** should be compiled without -DSQLITE_DEBUG and with -DNDEBUG to
74** make sure no assert() statements are evaluated and hence these
75** routines are never called.
76*/
chw97185482008-11-17 08:05:31[diff] [blame]77#if !defined(NDEBUG) || defined(SQLITE_DEBUG)
danielk19776d2ab0e2008-06-17 17:21:18[diff] [blame]78static int pthreadMutexHeld(sqlite3_mutex *p){
79 return (p->nRef!=0 && pthread_equal(p->owner, pthread_self()));
80}
81static int pthreadMutexNotheld(sqlite3_mutex *p){
82 return p->nRef==0 || pthread_equal(p->owner, pthread_self())==0;
83}
84#endif
85
86/*
drh539482b2015-09-26 03:23:29[diff] [blame]87** Try to provide a memory barrier operation, needed for initialization
88** and also for the implementation of xShmBarrier in the VFS in cases
89** where SQLite is compiled without mutexes.
drh6081c1d2015-09-06 02:51:04[diff] [blame]90*/
91void sqlite3MemoryBarrier(void){
drh2d640342015-09-06 10:31:37[diff] [blame]92#if defined(SQLITE_MEMORY_BARRIER)
drh6081c1d2015-09-06 02:51:04[diff] [blame]93 SQLITE_MEMORY_BARRIER;
mistachkin04abf082015-09-12 18:57:45[diff] [blame]94#elif defined(__GNUC__) && GCC_VERSION>=4001000
drh2d640342015-09-06 10:31:37[diff] [blame]95 __sync_synchronize();
drh6081c1d2015-09-06 02:51:04[diff] [blame]96#endif
97}
98
99/*
drh40257ff2008-06-13 18:24:27[diff] [blame]100** Initialize and deinitialize the mutex subsystem.
101*/
danielk19776d2ab0e2008-06-17 17:21:18[diff] [blame]102static int pthreadMutexInit(void){ return SQLITE_OK; }
103static int pthreadMutexEnd(void){ return SQLITE_OK; }
drh40257ff2008-06-13 18:24:27[diff] [blame]104
105/*
drh437b9012007-08-28 16:34:42[diff] [blame]106** The sqlite3_mutex_alloc() routine allocates a new
107** mutex and returns a pointer to it. If it returns NULL
108** that means that a mutex could not be allocated. SQLite
109** will unwind its stack and return an error. The argument
110** to sqlite3_mutex_alloc() is one of these integer constants:
111**
112** <ul>
113** <li> SQLITE_MUTEX_FAST
114** <li> SQLITE_MUTEX_RECURSIVE
drhccb21132020-06-19 11:34:57[diff] [blame]115** <li> SQLITE_MUTEX_STATIC_MAIN
drh437b9012007-08-28 16:34:42[diff] [blame]116** <li> SQLITE_MUTEX_STATIC_MEM
drhd42d0be2014-07-30 21:10:12[diff] [blame]117** <li> SQLITE_MUTEX_STATIC_OPEN
drh437b9012007-08-28 16:34:42[diff] [blame]118** <li> SQLITE_MUTEX_STATIC_PRNG
119** <li> SQLITE_MUTEX_STATIC_LRU
dan6d4fb832011-01-26 07:25:32[diff] [blame]120** <li> SQLITE_MUTEX_STATIC_PMEM
drhd42d0be2014-07-30 21:10:12[diff] [blame]121** <li> SQLITE_MUTEX_STATIC_APP1
122** <li> SQLITE_MUTEX_STATIC_APP2
123** <li> SQLITE_MUTEX_STATIC_APP3
mistachkin93de6532015-07-03 21:38:09[diff] [blame]124** <li> SQLITE_MUTEX_STATIC_VFS1
125** <li> SQLITE_MUTEX_STATIC_VFS2
126** <li> SQLITE_MUTEX_STATIC_VFS3
drh437b9012007-08-28 16:34:42[diff] [blame]127** </ul>
128**
129** The first two constants cause sqlite3_mutex_alloc() to create
130** a new mutex. The new mutex is recursive when SQLITE_MUTEX_RECURSIVE
131** is used but not necessarily so when SQLITE_MUTEX_FAST is used.
132** The mutex implementation does not need to make a distinction
133** between SQLITE_MUTEX_RECURSIVE and SQLITE_MUTEX_FAST if it does
134** not want to. But SQLite will only request a recursive mutex in
135** cases where it really needs one. If a faster non-recursive mutex
136** implementation is available on the host platform, the mutex subsystem
137** might return such a mutex in response to SQLITE_MUTEX_FAST.
138**
139** The other allowed parameters to sqlite3_mutex_alloc() each return
shane7c7c3112009-08-17 15:31:23[diff] [blame]140** a pointer to a static preexisting mutex. Six static mutexes are
drh437b9012007-08-28 16:34:42[diff] [blame]141** used by the current version of SQLite. Future versions of SQLite
142** may add additional static mutexes. Static mutexes are for internal
143** use by SQLite only. Applications that use SQLite mutexes should
144** use only the dynamic mutexes returned by SQLITE_MUTEX_FAST or
145** SQLITE_MUTEX_RECURSIVE.
146**
147** Note that if one of the dynamic mutex parameters (SQLITE_MUTEX_FAST
148** or SQLITE_MUTEX_RECURSIVE) is used then sqlite3_mutex_alloc()
larrybrbc917382023-06-07 08:40:31[diff] [blame]149** returns a different mutex on every call. But for the static
drh437b9012007-08-28 16:34:42[diff] [blame]150** mutex types, the same mutex is returned on every call that has
151** the same type number.
152*/
danielk19776d2ab0e2008-06-17 17:21:18[diff] [blame]153static sqlite3_mutex *pthreadMutexAlloc(int iType){
drh437b9012007-08-28 16:34:42[diff] [blame]154 static sqlite3_mutex staticMutexes[] = {
danc5515502018-02-17 07:38:50[diff] [blame]155 SQLITE3_MUTEX_INITIALIZER(2),
156 SQLITE3_MUTEX_INITIALIZER(3),
157 SQLITE3_MUTEX_INITIALIZER(4),
158 SQLITE3_MUTEX_INITIALIZER(5),
159 SQLITE3_MUTEX_INITIALIZER(6),
160 SQLITE3_MUTEX_INITIALIZER(7),
161 SQLITE3_MUTEX_INITIALIZER(8),
162 SQLITE3_MUTEX_INITIALIZER(9),
163 SQLITE3_MUTEX_INITIALIZER(10),
164 SQLITE3_MUTEX_INITIALIZER(11),
165 SQLITE3_MUTEX_INITIALIZER(12),
166 SQLITE3_MUTEX_INITIALIZER(13)
drh437b9012007-08-28 16:34:42[diff] [blame]167 };
168 sqlite3_mutex *p;
169 switch( iType ){
170 case SQLITE_MUTEX_RECURSIVE: {
171 p = sqlite3MallocZero( sizeof(*p) );
172 if( p ){
drh0167f282007-11-28 14:04:57[diff] [blame]173#ifdef SQLITE_HOMEGROWN_RECURSIVE_MUTEX
174 /* If recursive mutexes are not available, we will have to
175 ** build our own. See below. */
176 pthread_mutex_init(&p->mutex, 0);
177#else
drhed05efb2007-11-28 00:51:34[diff] [blame]178 /* Use a recursive mutex if it is available */
drh437b9012007-08-28 16:34:42[diff] [blame]179 pthread_mutexattr_t recursiveAttr;
180 pthread_mutexattr_init(&recursiveAttr);
181 pthread_mutexattr_settype(&recursiveAttr, PTHREAD_MUTEX_RECURSIVE);
182 pthread_mutex_init(&p->mutex, &recursiveAttr);
183 pthread_mutexattr_destroy(&recursiveAttr);
drhed05efb2007-11-28 00:51:34[diff] [blame]184#endif
danc5515502018-02-17 07:38:50[diff] [blame]185#if SQLITE_MUTEX_NREF || defined(SQLITE_ENABLE_API_ARMOR)
186 p->id = SQLITE_MUTEX_RECURSIVE;
187#endif
drh437b9012007-08-28 16:34:42[diff] [blame]188 }
189 break;
190 }
191 case SQLITE_MUTEX_FAST: {
192 p = sqlite3MallocZero( sizeof(*p) );
193 if( p ){
drh437b9012007-08-28 16:34:42[diff] [blame]194 pthread_mutex_init(&p->mutex, 0);
danc5515502018-02-17 07:38:50[diff] [blame]195#if SQLITE_MUTEX_NREF || defined(SQLITE_ENABLE_API_ARMOR)
196 p->id = SQLITE_MUTEX_FAST;
197#endif
drh437b9012007-08-28 16:34:42[diff] [blame]198 }
199 break;
200 }
201 default: {
drh9ca95732014-10-24 00:35:58[diff] [blame]202#ifdef SQLITE_ENABLE_API_ARMOR
203 if( iType-2<0 || iType-2>=ArraySize(staticMutexes) ){
204 (void)SQLITE_MISUSE_BKPT;
205 return 0;
206 }
207#endif
drh437b9012007-08-28 16:34:42[diff] [blame]208 p = &staticMutexes[iType-2];
drh437b9012007-08-28 16:34:42[diff] [blame]209 break;
210 }
211 }
drh96c707a2015-02-13 16:36:14[diff] [blame]212#if SQLITE_MUTEX_NREF || defined(SQLITE_ENABLE_API_ARMOR)
danc5515502018-02-17 07:38:50[diff] [blame]213 assert( p==0 || p->id==iType );
drh96c707a2015-02-13 16:36:14[diff] [blame]214#endif
drh437b9012007-08-28 16:34:42[diff] [blame]215 return p;
216}
217
218
219/*
220** This routine deallocates a previously
221** allocated mutex. SQLite is careful to deallocate every
222** mutex that it allocates.
223*/
danielk19776d2ab0e2008-06-17 17:21:18[diff] [blame]224static void pthreadMutexFree(sqlite3_mutex *p){
225 assert( p->nRef==0 );
stephan24f6bac2023-10-15 13:36:21[diff] [blame]226#ifdef SQLITE_ENABLE_API_ARMOR
drh96c707a2015-02-13 16:36:14[diff] [blame]227 if( p->id==SQLITE_MUTEX_FAST || p->id==SQLITE_MUTEX_RECURSIVE )
228#endif
229 {
230 pthread_mutex_destroy(&p->mutex);
231 sqlite3_free(p);
232 }
233#ifdef SQLITE_ENABLE_API_ARMOR
234 else{
235 (void)SQLITE_MISUSE_BKPT;
236 }
237#endif
drh437b9012007-08-28 16:34:42[diff] [blame]238}
239
240/*
241** The sqlite3_mutex_enter() and sqlite3_mutex_try() routines attempt
242** to enter a mutex. If another thread is already within the mutex,
243** sqlite3_mutex_enter() will block and sqlite3_mutex_try() will return
244** SQLITE_BUSY. The sqlite3_mutex_try() interface returns SQLITE_OK
245** upon successful entry. Mutexes created using SQLITE_MUTEX_RECURSIVE can
246** be entered multiple times by the same thread. In such cases the,
247** mutex must be exited an equal number of times before another thread
248** can enter. If the same thread tries to enter any other kind of mutex
249** more than once, the behavior is undefined.
250*/
danielk19776d2ab0e2008-06-17 17:21:18[diff] [blame]251static void pthreadMutexEnter(sqlite3_mutex *p){
252 assert( p->id==SQLITE_MUTEX_RECURSIVE || pthreadMutexNotheld(p) );
drhed05efb2007-11-28 00:51:34[diff] [blame]253
drh0167f282007-11-28 14:04:57[diff] [blame]254#ifdef SQLITE_HOMEGROWN_RECURSIVE_MUTEX
drhed05efb2007-11-28 00:51:34[diff] [blame]255 /* If recursive mutexes are not available, then we have to grow
256 ** our own. This implementation assumes that pthread_equal()
257 ** is atomic - that it cannot be deceived into thinking self
258 ** and p->owner are equal if p->owner changes between two values
259 ** that are not equal to self while the comparison is taking place.
larrybrbc917382023-06-07 08:40:31[diff] [blame]260 ** This implementation also assumes a coherent cache - that
drh5f3d6522007-11-28 13:55:55[diff] [blame]261 ** separate processes cannot read different values from the same
262 ** address at the same time. If either of these two conditions
263 ** are not met, then the mutexes will fail and problems will result.
drhed05efb2007-11-28 00:51:34[diff] [blame]264 */
265 {
266 pthread_t self = pthread_self();
267 if( p->nRef>0 && pthread_equal(p->owner, self) ){
268 p->nRef++;
269 }else{
270 pthread_mutex_lock(&p->mutex);
271 assert( p->nRef==0 );
272 p->owner = self;
273 p->nRef = 1;
274 }
275 }
drh0167f282007-11-28 14:04:57[diff] [blame]276#else
277 /* Use the built-in recursive mutexes if they are available.
278 */
279 pthread_mutex_lock(&p->mutex);
drh72339a32010-05-13 20:19:17[diff] [blame]280#if SQLITE_MUTEX_NREF
dan84612fe2010-08-10 07:12:26[diff] [blame]281 assert( p->nRef>0 || p->owner==0 );
drh0167f282007-11-28 14:04:57[diff] [blame]282 p->owner = pthread_self();
283 p->nRef++;
drhed05efb2007-11-28 00:51:34[diff] [blame]284#endif
drh72339a32010-05-13 20:19:17[diff] [blame]285#endif
drhed05efb2007-11-28 00:51:34[diff] [blame]286
drhd0679ed2007-08-28 22:24:34[diff] [blame]287#ifdef SQLITE_DEBUG
288 if( p->trace ){
289 printf("enter mutex %p (%d) with nRef=%d\n", p, p->trace, p->nRef);
290 }
291#endif
drh437b9012007-08-28 16:34:42[diff] [blame]292}
danielk19776d2ab0e2008-06-17 17:21:18[diff] [blame]293static int pthreadMutexTry(sqlite3_mutex *p){
drh437b9012007-08-28 16:34:42[diff] [blame]294 int rc;
danielk19776d2ab0e2008-06-17 17:21:18[diff] [blame]295 assert( p->id==SQLITE_MUTEX_RECURSIVE || pthreadMutexNotheld(p) );
drhed05efb2007-11-28 00:51:34[diff] [blame]296
drh0167f282007-11-28 14:04:57[diff] [blame]297#ifdef SQLITE_HOMEGROWN_RECURSIVE_MUTEX
drhed05efb2007-11-28 00:51:34[diff] [blame]298 /* If recursive mutexes are not available, then we have to grow
299 ** our own. This implementation assumes that pthread_equal()
300 ** is atomic - that it cannot be deceived into thinking self
301 ** and p->owner are equal if p->owner changes between two values
302 ** that are not equal to self while the comparison is taking place.
larrybrbc917382023-06-07 08:40:31[diff] [blame]303 ** This implementation also assumes a coherent cache - that
drh5f3d6522007-11-28 13:55:55[diff] [blame]304 ** separate processes cannot read different values from the same
305 ** address at the same time. If either of these two conditions
306 ** are not met, then the mutexes will fail and problems will result.
drhed05efb2007-11-28 00:51:34[diff] [blame]307 */
308 {
309 pthread_t self = pthread_self();
310 if( p->nRef>0 && pthread_equal(p->owner, self) ){
311 p->nRef++;
312 rc = SQLITE_OK;
drh3bbc0e72008-07-16 12:33:23[diff] [blame]313 }else if( pthread_mutex_trylock(&p->mutex)==0 ){
drhed05efb2007-11-28 00:51:34[diff] [blame]314 assert( p->nRef==0 );
315 p->owner = self;
316 p->nRef = 1;
317 rc = SQLITE_OK;
318 }else{
319 rc = SQLITE_BUSY;
320 }
321 }
drh0167f282007-11-28 14:04:57[diff] [blame]322#else
323 /* Use the built-in recursive mutexes if they are available.
324 */
325 if( pthread_mutex_trylock(&p->mutex)==0 ){
drh72339a32010-05-13 20:19:17[diff] [blame]326#if SQLITE_MUTEX_NREF
drh0167f282007-11-28 14:04:57[diff] [blame]327 p->owner = pthread_self();
328 p->nRef++;
drh72339a32010-05-13 20:19:17[diff] [blame]329#endif
drh0167f282007-11-28 14:04:57[diff] [blame]330 rc = SQLITE_OK;
331 }else{
332 rc = SQLITE_BUSY;
333 }
drhed05efb2007-11-28 00:51:34[diff] [blame]334#endif
335
336#ifdef SQLITE_DEBUG
337 if( rc==SQLITE_OK && p->trace ){
338 printf("enter mutex %p (%d) with nRef=%d\n", p, p->trace, p->nRef);
339 }
340#endif
drh437b9012007-08-28 16:34:42[diff] [blame]341 return rc;
342}
343
344/*
345** The sqlite3_mutex_leave() routine exits a mutex that was
346** previously entered by the same thread. The behavior
347** is undefined if the mutex is not currently entered or
348** is not currently allocated. SQLite will never do either.
349*/
danielk19776d2ab0e2008-06-17 17:21:18[diff] [blame]350static void pthreadMutexLeave(sqlite3_mutex *p){
danielk19771a9ed0b2008-06-18 09:45:56[diff] [blame]351 assert( pthreadMutexHeld(p) );
drh72339a32010-05-13 20:19:17[diff] [blame]352#if SQLITE_MUTEX_NREF
drh437b9012007-08-28 16:34:42[diff] [blame]353 p->nRef--;
dan84612fe2010-08-10 07:12:26[diff] [blame]354 if( p->nRef==0 ) p->owner = 0;
drh72339a32010-05-13 20:19:17[diff] [blame]355#endif
drh437b9012007-08-28 16:34:42[diff] [blame]356 assert( p->nRef==0 || p->id==SQLITE_MUTEX_RECURSIVE );
drhed05efb2007-11-28 00:51:34[diff] [blame]357
drh0167f282007-11-28 14:04:57[diff] [blame]358#ifdef SQLITE_HOMEGROWN_RECURSIVE_MUTEX
drhed05efb2007-11-28 00:51:34[diff] [blame]359 if( p->nRef==0 ){
360 pthread_mutex_unlock(&p->mutex);
361 }
drh0167f282007-11-28 14:04:57[diff] [blame]362#else
363 pthread_mutex_unlock(&p->mutex);
drhed05efb2007-11-28 00:51:34[diff] [blame]364#endif
365
drhd0679ed2007-08-28 22:24:34[diff] [blame]366#ifdef SQLITE_DEBUG
367 if( p->trace ){
368 printf("leave mutex %p (%d) with nRef=%d\n", p, p->trace, p->nRef);
369 }
370#endif
drh437b9012007-08-28 16:34:42[diff] [blame]371}
372
dan558814f2010-06-02 05:53:53[diff] [blame]373sqlite3_mutex_methods const *sqlite3DefaultMutex(void){
374 static const sqlite3_mutex_methods sMutex = {
danielk19776d2ab0e2008-06-17 17:21:18[diff] [blame]375 pthreadMutexInit,
danielk19774a9d1f62008-06-19 08:51:23[diff] [blame]376 pthreadMutexEnd,
danielk19776d2ab0e2008-06-17 17:21:18[diff] [blame]377 pthreadMutexAlloc,
378 pthreadMutexFree,
379 pthreadMutexEnter,
380 pthreadMutexTry,
381 pthreadMutexLeave,
drha4189802008-06-19 16:07:07[diff] [blame]382#ifdef SQLITE_DEBUG
danielk19776d2ab0e2008-06-17 17:21:18[diff] [blame]383 pthreadMutexHeld,
384 pthreadMutexNotheld
drh1875f7a2008-12-08 18:19:17[diff] [blame]385#else
386 0,
387 0
drha4189802008-06-19 16:07:07[diff] [blame]388#endif
danielk19776d2ab0e2008-06-17 17:21:18[diff] [blame]389 };
390
391 return &sMutex;
drh437b9012007-08-28 16:34:42[diff] [blame]392}
danielk19776d2ab0e2008-06-17 17:21:18[diff] [blame]393
drhe4c88c02012-01-04 12:57:45[diff] [blame]394#endif /* SQLITE_MUTEX_PTHREADS */