237 lines
7.6 KiB
C
Executable File
237 lines
7.6 KiB
C
Executable File
/*
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** 2007 August 28
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**
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** The author disclaims copyright to this source code. In place of
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** a legal notice, here is a blessing:
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**
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** May you do good and not evil.
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** May you find forgiveness for yourself and forgive others.
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** May you share freely, never taking more than you give.
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**
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*************************************************************************
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** This file contains the C functions that implement mutexes for OS/2
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**
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** $Id: mutex_os2.c,v 1.3 2007/10/02 19:56:04 pweilbacher Exp $
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*/
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#include "sqliteInt.h"
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/*
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** The code in this file is only used if SQLITE_MUTEX_OS2 is defined.
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** See the mutex.h file for details.
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*/
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#ifdef SQLITE_MUTEX_OS2
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/********************** OS/2 Mutex Implementation **********************
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**
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** This implementation of mutexes is built using the OS/2 API.
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*/
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/*
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** The mutex object
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** Each recursive mutex is an instance of the following structure.
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*/
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struct sqlite3_mutex {
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PSZ mutexName; /* Mutex name controlling the lock */
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HMTX mutex; /* Mutex controlling the lock */
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int id; /* Mutex type */
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int nRef; /* Number of references */
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TID owner; /* Thread holding this mutex */
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};
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/*
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** The sqlite3_mutex_alloc() routine allocates a new
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** mutex and returns a pointer to it. If it returns NULL
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** that means that a mutex could not be allocated.
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** SQLite will unwind its stack and return an error. The argument
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** to sqlite3_mutex_alloc() is one of these integer constants:
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**
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** <ul>
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** <li> SQLITE_MUTEX_FAST 0
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** <li> SQLITE_MUTEX_RECURSIVE 1
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** <li> SQLITE_MUTEX_STATIC_MASTER 2
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** <li> SQLITE_MUTEX_STATIC_MEM 3
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** <li> SQLITE_MUTEX_STATIC_PRNG 4
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** </ul>
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**
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** The first two constants cause sqlite3_mutex_alloc() to create
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** a new mutex. The new mutex is recursive when SQLITE_MUTEX_RECURSIVE
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** is used but not necessarily so when SQLITE_MUTEX_FAST is used.
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** The mutex implementation does not need to make a distinction
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** between SQLITE_MUTEX_RECURSIVE and SQLITE_MUTEX_FAST if it does
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** not want to. But SQLite will only request a recursive mutex in
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** cases where it really needs one. If a faster non-recursive mutex
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** implementation is available on the host platform, the mutex subsystem
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** might return such a mutex in response to SQLITE_MUTEX_FAST.
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**
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** The other allowed parameters to sqlite3_mutex_alloc() each return
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** a pointer to a static preexisting mutex. Three static mutexes are
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** used by the current version of SQLite. Future versions of SQLite
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** may add additional static mutexes. Static mutexes are for internal
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** use by SQLite only. Applications that use SQLite mutexes should
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** use only the dynamic mutexes returned by SQLITE_MUTEX_FAST or
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** SQLITE_MUTEX_RECURSIVE.
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**
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** Note that if one of the dynamic mutex parameters (SQLITE_MUTEX_FAST
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** or SQLITE_MUTEX_RECURSIVE) is used then sqlite3_mutex_alloc()
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** returns a different mutex on every call. But for the static
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** mutex types, the same mutex is returned on every call that has
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** the same type number.
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*/
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sqlite3_mutex *sqlite3_mutex_alloc(int iType){
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PSZ mutex_name = "\\SEM32\\SQLITE\\MUTEX";
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int mutex_name_len = strlen(mutex_name) + 1; /* name length + null byte */
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sqlite3_mutex *p;
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switch( iType ){
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case SQLITE_MUTEX_FAST:
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case SQLITE_MUTEX_RECURSIVE: {
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p = sqlite3MallocZero( sizeof(*p) );
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if( p ){
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p->mutexName = (PSZ)malloc(mutex_name_len);
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sqlite3_snprintf(mutex_name_len, p->mutexName, "%s", mutex_name);
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p->id = iType;
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DosCreateMutexSem(p->mutexName, &p->mutex, 0, FALSE);
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DosOpenMutexSem(p->mutexName, &p->mutex);
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}
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break;
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}
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default: {
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static sqlite3_mutex staticMutexes[5];
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static int isInit = 0;
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while( !isInit ) {
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static long lock = 0;
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DosEnterCritSec();
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lock++;
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if( lock == 1 ) {
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DosExitCritSec();
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int i;
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for(i = 0; i < sizeof(staticMutexes)/sizeof(staticMutexes[0]); i++) {
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staticMutexes[i].mutexName = (PSZ)malloc(mutex_name_len + 1);
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sqlite3_snprintf(mutex_name_len + 1, /* one more for the number */
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staticMutexes[i].mutexName, "%s%1d", mutex_name, i);
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DosCreateMutexSem(staticMutexes[i].mutexName,
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&staticMutexes[i].mutex, 0, FALSE);
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DosOpenMutexSem(staticMutexes[i].mutexName,
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&staticMutexes[i].mutex);
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}
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isInit = 1;
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} else {
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DosExitCritSec();
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DosSleep(1);
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}
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}
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assert( iType-2 >= 0 );
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assert( iType-2 < sizeof(staticMutexes)/sizeof(staticMutexes[0]) );
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p = &staticMutexes[iType-2];
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p->id = iType;
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break;
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}
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}
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return p;
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}
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/*
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** This routine deallocates a previously allocated mutex.
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** SQLite is careful to deallocate every mutex that it allocates.
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*/
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void sqlite3_mutex_free(sqlite3_mutex *p){
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assert( p );
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assert( p->nRef==0 );
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assert( p->id==SQLITE_MUTEX_FAST || p->id==SQLITE_MUTEX_RECURSIVE );
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DosCloseMutexSem(p->mutex);
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free(p->mutexName);
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sqlite3_free(p);
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}
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/*
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** The sqlite3_mutex_enter() and sqlite3_mutex_try() routines attempt
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** to enter a mutex. If another thread is already within the mutex,
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** sqlite3_mutex_enter() will block and sqlite3_mutex_try() will return
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** SQLITE_BUSY. The sqlite3_mutex_try() interface returns SQLITE_OK
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** upon successful entry. Mutexes created using SQLITE_MUTEX_RECURSIVE can
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** be entered multiple times by the same thread. In such cases the,
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** mutex must be exited an equal number of times before another thread
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** can enter. If the same thread tries to enter any other kind of mutex
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** more than once, the behavior is undefined.
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*/
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void sqlite3_mutex_enter(sqlite3_mutex *p){
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TID tid;
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PID holder1;
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ULONG holder2;
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assert( p );
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assert( p->id==SQLITE_MUTEX_RECURSIVE || sqlite3_mutex_notheld(p) );
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DosRequestMutexSem(p->mutex, SEM_INDEFINITE_WAIT);
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DosQueryMutexSem(p->mutex, &holder1, &tid, &holder2);
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p->owner = tid;
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p->nRef++;
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}
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int sqlite3_mutex_try(sqlite3_mutex *p){
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int rc;
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TID tid;
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PID holder1;
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ULONG holder2;
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assert( p );
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assert( p->id==SQLITE_MUTEX_RECURSIVE || sqlite3_mutex_notheld(p) );
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if( DosRequestMutexSem(p->mutex, SEM_IMMEDIATE_RETURN) == NO_ERROR) {
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DosQueryMutexSem(p->mutex, &holder1, &tid, &holder2);
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p->owner = tid;
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p->nRef++;
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rc = SQLITE_OK;
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} else {
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rc = SQLITE_BUSY;
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}
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return rc;
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}
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/*
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** The sqlite3_mutex_leave() routine exits a mutex that was
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** previously entered by the same thread. The behavior
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** is undefined if the mutex is not currently entered or
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** is not currently allocated. SQLite will never do either.
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*/
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void sqlite3_mutex_leave(sqlite3_mutex *p){
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TID tid;
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PID holder1;
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ULONG holder2;
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assert( p->nRef>0 );
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DosQueryMutexSem(p->mutex, &holder1, &tid, &holder2);
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assert( p->owner==tid );
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p->nRef--;
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assert( p->nRef==0 || p->id==SQLITE_MUTEX_RECURSIVE );
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DosReleaseMutexSem(p->mutex);
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}
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/*
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** The sqlite3_mutex_held() and sqlite3_mutex_notheld() routine are
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** intended for use inside assert() statements.
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*/
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int sqlite3_mutex_held(sqlite3_mutex *p){
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TID tid;
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PID pid;
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ULONG ulCount;
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PTIB ptib;
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if( p!=0 ) {
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DosQueryMutexSem(p->mutex, &pid, &tid, &ulCount);
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} else {
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DosGetInfoBlocks(&ptib, NULL);
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tid = ptib->tib_ptib2->tib2_ultid;
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}
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return p==0 || (p->nRef!=0 && p->owner==tid);
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}
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int sqlite3_mutex_notheld(sqlite3_mutex *p){
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TID tid;
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PID pid;
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ULONG ulCount;
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PTIB ptib;
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if( p!= 0 ) {
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DosQueryMutexSem(p->mutex, &pid, &tid, &ulCount);
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} else {
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DosGetInfoBlocks(&ptib, NULL);
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tid = ptib->tib_ptib2->tib2_ultid;
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}
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return p==0 || p->nRef==0 || p->owner!=tid;
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}
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#endif /* SQLITE_MUTEX_OS2 */
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