sqlcipher/src/mutex.c at sqlite-release · securitykernel/sqlcipher · GitHub

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** 2007 August 14

** The author disclaims copyright to this source code. In place of

** a legal notice, here is a blessing:

** May you do good and not evil.

** May you find forgiveness for yourself and forgive others.

** May you share freely, never taking more than you give.

*************************************************************************

** This file contains the C functions that implement mutexes.

** This file contains code that is common across all mutex implementations.

#include "sqliteInt.h"

#if defined(SQLITE_DEBUG) && !defined(SQLITE_MUTEX_OMIT)

** For debugging purposes, record when the mutex subsystem is initialized

** and uninitialized so that we can assert() if there is an attempt to

** allocate a mutex while the system is uninitialized.

static SQLITE_WSD int mutexIsInit = 0;

#endif /* SQLITE_DEBUG && !defined(SQLITE_MUTEX_OMIT) */

#ifndef SQLITE_MUTEX_OMIT

#ifdef SQLITE_ENABLE_MULTITHREADED_CHECKS

** This block (enclosed by SQLITE_ENABLE_MULTITHREADED_CHECKS) contains

** the implementation of a wrapper around the system default mutex

** implementation (sqlite3DefaultMutex()).

** Most calls are passed directly through to the underlying default

** mutex implementation. Except, if a mutex is configured by calling

** sqlite3MutexWarnOnContention() on it, then if contention is ever

** encountered within xMutexEnter() a warning is emitted via sqlite3_log().

** This type of mutex is used as the database handle mutex when testing

** apps that usually use SQLITE_CONFIG_MULTITHREAD mode.

** Type for all mutexes used when SQLITE_ENABLE_MULTITHREADED_CHECKS

** is defined. Variable CheckMutex.mutex is a pointer to the real mutex

** allocated by the system mutex implementation. Variable iType is usually set

** to the type of mutex requested - SQLITE_MUTEX_RECURSIVE, SQLITE_MUTEX_FAST

** or one of the static mutex identifiers. Or, if this is a recursive mutex

** that has been configured using sqlite3MutexWarnOnContention(), it is

** set to SQLITE_MUTEX_WARNONCONTENTION.

typedef struct CheckMutex CheckMutex;

struct CheckMutex {

int iType;

sqlite3_mutex *mutex;

};

#define SQLITE_MUTEX_WARNONCONTENTION (-1)

** Pointer to real mutex methods object used by the CheckMutex

** implementation. Set by checkMutexInit().

static SQLITE_WSD const sqlite3_mutex_methods *pGlobalMutexMethods;

#ifdef SQLITE_DEBUG

static int checkMutexHeld(sqlite3_mutex *p){

return pGlobalMutexMethods->xMutexHeld(((CheckMutex*)p)->mutex);

}

static int checkMutexNotheld(sqlite3_mutex *p){

return pGlobalMutexMethods->xMutexNotheld(((CheckMutex*)p)->mutex);

}

#endif

** Initialize and deinitialize the mutex subsystem.

static int checkMutexInit(void){

pGlobalMutexMethods = sqlite3DefaultMutex();

return SQLITE_OK;

}

static int checkMutexEnd(void){

pGlobalMutexMethods = 0;

return SQLITE_OK;

}

** Allocate a mutex.

static sqlite3_mutex *checkMutexAlloc(int iType){

static CheckMutex staticMutexes[] = {

{2, 0}, {3, 0}, {4, 0}, {5, 0},

{6, 0}, {7, 0}, {8, 0}, {9, 0},

{10, 0}, {11, 0}, {12, 0}, {13, 0}

};

CheckMutex *p = 0;

assert( SQLITE_MUTEX_RECURSIVE==1 && SQLITE_MUTEX_FAST==0 );

if( iType<2 ){

p = sqlite3MallocZero(sizeof(CheckMutex));

if( p==0 ) return 0;

p->iType = iType;

}else{

#ifdef SQLITE_ENABLE_API_ARMOR

if( iType-2>=ArraySize(staticMutexes) ){

(void)SQLITE_MISUSE_BKPT;

return 0;

}

#endif

p = &staticMutexes[iType-2];

}

if( p->mutex==0 ){

p->mutex = pGlobalMutexMethods->xMutexAlloc(iType);

if( p->mutex==0 ){

if( iType<2 ){

sqlite3_free(p);

}

p = 0;

}

return (sqlite3_mutex*)p;

}

** Free a mutex.

static void checkMutexFree(sqlite3_mutex *p){

assert( SQLITE_MUTEX_RECURSIVE<2 );

assert( SQLITE_MUTEX_FAST<2 );

assert( SQLITE_MUTEX_WARNONCONTENTION<2 );

#if SQLITE_ENABLE_API_ARMOR

if( ((CheckMutex*)p)->iType<2 )

#endif

{

CheckMutex *pCheck = (CheckMutex*)p;

pGlobalMutexMethods->xMutexFree(pCheck->mutex);

sqlite3_free(pCheck);

}

#ifdef SQLITE_ENABLE_API_ARMOR

else{

(void)SQLITE_MISUSE_BKPT;

}

#endif

}

** Enter the mutex.

static void checkMutexEnter(sqlite3_mutex *p){

CheckMutex *pCheck = (CheckMutex*)p;

if( pCheck->iType==SQLITE_MUTEX_WARNONCONTENTION ){

if( SQLITE_OK==pGlobalMutexMethods->xMutexTry(pCheck->mutex) ){

return;

}

sqlite3_log(SQLITE_MISUSE,

"illegal multi-threaded access to database connection"

);

}

pGlobalMutexMethods->xMutexEnter(pCheck->mutex);

}

** Enter the mutex (do not block).

static int checkMutexTry(sqlite3_mutex *p){

CheckMutex *pCheck = (CheckMutex*)p;

return pGlobalMutexMethods->xMutexTry(pCheck->mutex);

}

** Leave the mutex.

static void checkMutexLeave(sqlite3_mutex *p){

CheckMutex *pCheck = (CheckMutex*)p;

pGlobalMutexMethods->xMutexLeave(pCheck->mutex);

}

sqlite3_mutex_methods const *multiThreadedCheckMutex(void){

static const sqlite3_mutex_methods sMutex = {

checkMutexInit,

checkMutexEnd,

checkMutexAlloc,

checkMutexFree,

checkMutexEnter,

checkMutexTry,

checkMutexLeave,

#ifdef SQLITE_DEBUG

checkMutexHeld,

checkMutexNotheld

#else

#endif

};

return &sMutex;

}

** Mark the SQLITE_MUTEX_RECURSIVE mutex passed as the only argument as

** one on which there should be no contention.

void sqlite3MutexWarnOnContention(sqlite3_mutex *p){

if( sqlite3GlobalConfig.mutex.xMutexAlloc==checkMutexAlloc ){

CheckMutex *pCheck = (CheckMutex*)p;

assert( pCheck->iType==SQLITE_MUTEX_RECURSIVE );

pCheck->iType = SQLITE_MUTEX_WARNONCONTENTION;

}

#endif /* ifdef SQLITE_ENABLE_MULTITHREADED_CHECKS */

** Initialize the mutex system.

int sqlite3MutexInit(void){

int rc = SQLITE_OK;

if( !sqlite3GlobalConfig.mutex.xMutexAlloc ){

/* If the xMutexAlloc method has not been set, then the user did not

** install a mutex implementation via sqlite3_config() prior to

** sqlite3_initialize() being called. This block copies pointers to

** the default implementation into the sqlite3GlobalConfig structure.

sqlite3_mutex_methods const *pFrom;

sqlite3_mutex_methods *pTo = &sqlite3GlobalConfig.mutex;

if( sqlite3GlobalConfig.bCoreMutex ){

#ifdef SQLITE_ENABLE_MULTITHREADED_CHECKS

pFrom = multiThreadedCheckMutex();

#else

pFrom = sqlite3DefaultMutex();

#endif

}else{

pFrom = sqlite3NoopMutex();

}

pTo->xMutexInit = pFrom->xMutexInit;

pTo->xMutexEnd = pFrom->xMutexEnd;

pTo->xMutexFree = pFrom->xMutexFree;

pTo->xMutexEnter = pFrom->xMutexEnter;

pTo->xMutexTry = pFrom->xMutexTry;

pTo->xMutexLeave = pFrom->xMutexLeave;

pTo->xMutexHeld = pFrom->xMutexHeld;

pTo->xMutexNotheld = pFrom->xMutexNotheld;

sqlite3MemoryBarrier();

pTo->xMutexAlloc = pFrom->xMutexAlloc;

}

assert( sqlite3GlobalConfig.mutex.xMutexInit );

rc = sqlite3GlobalConfig.mutex.xMutexInit();

#ifdef SQLITE_DEBUG

GLOBAL(int, mutexIsInit) = 1;

#endif

return rc;

}

** Shutdown the mutex system. This call frees resources allocated by

** sqlite3MutexInit().

int sqlite3MutexEnd(void){

int rc = SQLITE_OK;

if( sqlite3GlobalConfig.mutex.xMutexEnd ){

rc = sqlite3GlobalConfig.mutex.xMutexEnd();

}

#ifdef SQLITE_DEBUG

GLOBAL(int, mutexIsInit) = 0;

#endif

return rc;

}

** Retrieve a pointer to a static mutex or allocate a new dynamic one.

sqlite3_mutex *sqlite3_mutex_alloc(int id){

#ifndef SQLITE_OMIT_AUTOINIT

if( id<=SQLITE_MUTEX_RECURSIVE && sqlite3_initialize() ) return 0;

if( id>SQLITE_MUTEX_RECURSIVE && sqlite3MutexInit() ) return 0;

#endif

assert( sqlite3GlobalConfig.mutex.xMutexAlloc );

return sqlite3GlobalConfig.mutex.xMutexAlloc(id);

}

sqlite3_mutex *sqlite3MutexAlloc(int id){

if( !sqlite3GlobalConfig.bCoreMutex ){

return 0;

}

assert( GLOBAL(int, mutexIsInit) );

assert( sqlite3GlobalConfig.mutex.xMutexAlloc );

return sqlite3GlobalConfig.mutex.xMutexAlloc(id);

}

** Free a dynamic mutex.

void sqlite3_mutex_free(sqlite3_mutex *p){

if( p ){

assert( sqlite3GlobalConfig.mutex.xMutexFree );

sqlite3GlobalConfig.mutex.xMutexFree(p);

}

** Obtain the mutex p. If some other thread already has the mutex, block

** until it can be obtained.

void sqlite3_mutex_enter(sqlite3_mutex *p){

if( p ){

assert( sqlite3GlobalConfig.mutex.xMutexEnter );

sqlite3GlobalConfig.mutex.xMutexEnter(p);

}

** Obtain the mutex p. If successful, return SQLITE_OK. Otherwise, if another

** thread holds the mutex and it cannot be obtained, return SQLITE_BUSY.

int sqlite3_mutex_try(sqlite3_mutex *p){

int rc = SQLITE_OK;

if( p ){

assert( sqlite3GlobalConfig.mutex.xMutexTry );

return sqlite3GlobalConfig.mutex.xMutexTry(p);

}

return rc;

}

** The sqlite3_mutex_leave() routine exits a mutex that was previously

** entered by the same thread. The behavior is undefined if the mutex

** is not currently entered. If a NULL pointer is passed as an argument

** this function is a no-op.

void sqlite3_mutex_leave(sqlite3_mutex *p){

if( p ){

assert( sqlite3GlobalConfig.mutex.xMutexLeave );

sqlite3GlobalConfig.mutex.xMutexLeave(p);

}

#ifndef NDEBUG

** The sqlite3_mutex_held() and sqlite3_mutex_notheld() routine are

** intended for use inside assert() statements.

int sqlite3_mutex_held(sqlite3_mutex *p){

assert( p==0 || sqlite3GlobalConfig.mutex.xMutexHeld );

return p==0 || sqlite3GlobalConfig.mutex.xMutexHeld(p);

}

int sqlite3_mutex_notheld(sqlite3_mutex *p){

assert( p==0 || sqlite3GlobalConfig.mutex.xMutexNotheld );

return p==0 || sqlite3GlobalConfig.mutex.xMutexNotheld(p);

}

#endif

#endif /* !defined(SQLITE_MUTEX_OMIT) */

sqlcipher/src/mutex.c at sqlite-release · securitykernel/sqlcipher · GitHub

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