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399 lines (374 loc) · 11.5 KB
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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 for Win32.
*/
#include "sqliteInt.h"
#if SQLITE_OS_WIN
/*
** Include code that is common to all os_*.c files
*/
#include "os_common.h"
/*
** Include the header file for the Windows VFS.
*/
#include "os_win.h"
#endif
/*
** The code in this file is only used if we are compiling multithreaded
** on a Win32 system.
*/
#ifdef SQLITE_MUTEX_W32
/*
** Each recursive mutex is an instance of the following structure.
*/
struct sqlite3_mutex {
CRITICAL_SECTION mutex; /* Mutex controlling the lock */
int id; /* Mutex type */
#ifdef SQLITE_DEBUG
volatile int nRef; /* Number of enterances */
volatile DWORD owner; /* Thread holding this mutex */
volatile int trace; /* True to trace changes */
#endif
};
/*
** These are the initializer values used when declaring a "static" mutex
** on Win32. It should be noted that all mutexes require initialization
** on the Win32 platform.
*/
#define SQLITE_W32_MUTEX_INITIALIZER { 0 }
#ifdef SQLITE_DEBUG
#define SQLITE3_MUTEX_INITIALIZER { SQLITE_W32_MUTEX_INITIALIZER, 0, \
0L, (DWORD)0, 0 }
#else
#define SQLITE3_MUTEX_INITIALIZER { SQLITE_W32_MUTEX_INITIALIZER, 0 }
#endif
#ifdef SQLITE_DEBUG
/*
** The sqlite3_mutex_held() and sqlite3_mutex_notheld() routine are
** intended for use only inside assert() statements.
*/
static int winMutexHeld(sqlite3_mutex *p){
return p->nRef!=0 && p->owner==GetCurrentThreadId();
}
static int winMutexNotheld2(sqlite3_mutex *p, DWORD tid){
return p->nRef==0 || p->owner!=tid;
}
static int winMutexNotheld(sqlite3_mutex *p){
DWORD tid = GetCurrentThreadId();
return winMutexNotheld2(p, tid);
}
#endif
/*
** Try to provide a memory barrier operation, needed for initialization
** and also for the xShmBarrier method of the VFS in cases when SQLite is
** compiled without mutexes (SQLITE_THREADSAFE=0).
*/
void sqlite3MemoryBarrier(void){
#if defined(SQLITE_MEMORY_BARRIER)
SQLITE_MEMORY_BARRIER;
#elif defined(__GNUC__)
__sync_synchronize();
#elif MSVC_VERSION>=1300
_ReadWriteBarrier();
#elif defined(MemoryBarrier)
MemoryBarrier();
#endif
}
/*
** Initialize and deinitialize the mutex subsystem.
*/
static sqlite3_mutex winMutex_staticMutexes[] = {
SQLITE3_MUTEX_INITIALIZER,
SQLITE3_MUTEX_INITIALIZER,
SQLITE3_MUTEX_INITIALIZER,
SQLITE3_MUTEX_INITIALIZER,
SQLITE3_MUTEX_INITIALIZER,
SQLITE3_MUTEX_INITIALIZER,
SQLITE3_MUTEX_INITIALIZER,
SQLITE3_MUTEX_INITIALIZER,
SQLITE3_MUTEX_INITIALIZER,
SQLITE3_MUTEX_INITIALIZER,
SQLITE3_MUTEX_INITIALIZER,
SQLITE3_MUTEX_INITIALIZER
};
static int winMutex_isInit = 0;
static int winMutex_isNt = -1; /* <0 means "need to query" */
/* As the winMutexInit() and winMutexEnd() functions are called as part
** of the sqlite3_initialize() and sqlite3_shutdown() processing, the
** "interlocked" magic used here is probably not strictly necessary.
*/
static LONG SQLITE_WIN32_VOLATILE winMutex_lock = 0;
int sqlite3_win32_is_nt(void); /* os_win.c */
void sqlite3_win32_sleep(DWORD milliseconds); /* os_win.c */
static int winMutexInit(void){
/* The first to increment to 1 does actual initialization */
if( InterlockedCompareExchange(&winMutex_lock, 1, 0)==0 ){
int i;
for(i=0; i<ArraySize(winMutex_staticMutexes); i++){
#if SQLITE_OS_WINRT
InitializeCriticalSectionEx(&winMutex_staticMutexes[i].mutex, 0, 0);
#else
InitializeCriticalSection(&winMutex_staticMutexes[i].mutex);
#endif
}
winMutex_isInit = 1;
}else{
/* Another thread is (in the process of) initializing the static
** mutexes */
while( !winMutex_isInit ){
sqlite3_win32_sleep(1);
}
}
return SQLITE_OK;
}
static int winMutexEnd(void){
/* The first to decrement to 0 does actual shutdown
** (which should be the last to shutdown.) */
if( InterlockedCompareExchange(&winMutex_lock, 0, 1)==1 ){
if( winMutex_isInit==1 ){
int i;
for(i=0; i<ArraySize(winMutex_staticMutexes); i++){
DeleteCriticalSection(&winMutex_staticMutexes[i].mutex);
}
winMutex_isInit = 0;
}
}
return SQLITE_OK;
}
/*
** The sqlite3_mutex_alloc() routine allocates a new
** mutex and returns a pointer to it. If it returns NULL
** that means that a mutex could not be allocated. SQLite
** will unwind its stack and return an error. The argument
** to sqlite3_mutex_alloc() is one of these integer constants:
**
** <ul>
** <li> SQLITE_MUTEX_FAST
** <li> SQLITE_MUTEX_RECURSIVE
** <li> SQLITE_MUTEX_STATIC_MASTER
** <li> SQLITE_MUTEX_STATIC_MEM
** <li> SQLITE_MUTEX_STATIC_OPEN
** <li> SQLITE_MUTEX_STATIC_PRNG
** <li> SQLITE_MUTEX_STATIC_LRU
** <li> SQLITE_MUTEX_STATIC_PMEM
** <li> SQLITE_MUTEX_STATIC_APP1
** <li> SQLITE_MUTEX_STATIC_APP2
** <li> SQLITE_MUTEX_STATIC_APP3
** <li> SQLITE_MUTEX_STATIC_VFS1
** <li> SQLITE_MUTEX_STATIC_VFS2
** <li> SQLITE_MUTEX_STATIC_VFS3
** </ul>
**
** The first two constants cause sqlite3_mutex_alloc() to create
** a new mutex. The new mutex is recursive when SQLITE_MUTEX_RECURSIVE
** is used but not necessarily so when SQLITE_MUTEX_FAST is used.
** The mutex implementation does not need to make a distinction
** between SQLITE_MUTEX_RECURSIVE and SQLITE_MUTEX_FAST if it does
** not want to. But SQLite will only request a recursive mutex in
** cases where it really needs one. If a faster non-recursive mutex
** implementation is available on the host platform, the mutex subsystem
** might return such a mutex in response to SQLITE_MUTEX_FAST.
**
** The other allowed parameters to sqlite3_mutex_alloc() each return
** a pointer to a static preexisting mutex. Six static mutexes are
** used by the current version of SQLite. Future versions of SQLite
** may add additional static mutexes. Static mutexes are for internal
** use by SQLite only. Applications that use SQLite mutexes should
** use only the dynamic mutexes returned by SQLITE_MUTEX_FAST or
** SQLITE_MUTEX_RECURSIVE.
**
** Note that if one of the dynamic mutex parameters (SQLITE_MUTEX_FAST
** or SQLITE_MUTEX_RECURSIVE) is used then sqlite3_mutex_alloc()
** returns a different mutex on every call. But for the static
** mutex types, the same mutex is returned on every call that has
** the same type number.
*/
static sqlite3_mutex *winMutexAlloc(int iType){
sqlite3_mutex *p;
switch( iType ){
case SQLITE_MUTEX_FAST:
case SQLITE_MUTEX_RECURSIVE: {
p = sqlite3MallocZero( sizeof(*p) );
if( p ){
p->id = iType;
#ifdef SQLITE_DEBUG
#ifdef SQLITE_WIN32_MUTEX_TRACE_DYNAMIC
p->trace = 1;
#endif
#endif
#if SQLITE_OS_WINRT
InitializeCriticalSectionEx(&p->mutex, 0, 0);
#else
InitializeCriticalSection(&p->mutex);
#endif
}
break;
}
default: {
#ifdef SQLITE_ENABLE_API_ARMOR
if( iType-2<0 || iType-2>=ArraySize(winMutex_staticMutexes) ){
(void)SQLITE_MISUSE_BKPT;
return 0;
}
#endif
p = &winMutex_staticMutexes[iType-2];
p->id = iType;
#ifdef SQLITE_DEBUG
#ifdef SQLITE_WIN32_MUTEX_TRACE_STATIC
p->trace = 1;
#endif
#endif
break;
}
}
return p;
}
/*
** This routine deallocates a previously
** allocated mutex. SQLite is careful to deallocate every
** mutex that it allocates.
*/
static void winMutexFree(sqlite3_mutex *p){
assert( p );
assert( p->nRef==0 && p->owner==0 );
if( p->id==SQLITE_MUTEX_FAST || p->id==SQLITE_MUTEX_RECURSIVE ){
DeleteCriticalSection(&p->mutex);
sqlite3_free(p);
}else{
#ifdef SQLITE_ENABLE_API_ARMOR
(void)SQLITE_MISUSE_BKPT;
#endif
}
}
/*
** The sqlite3_mutex_enter() and sqlite3_mutex_try() routines attempt
** to enter a mutex. If another thread is already within the mutex,
** sqlite3_mutex_enter() will block and sqlite3_mutex_try() will return
** SQLITE_BUSY. The sqlite3_mutex_try() interface returns SQLITE_OK
** upon successful entry. Mutexes created using SQLITE_MUTEX_RECURSIVE can
** be entered multiple times by the same thread. In such cases the,
** mutex must be exited an equal number of times before another thread
** can enter. If the same thread tries to enter any other kind of mutex
** more than once, the behavior is undefined.
*/
static void winMutexEnter(sqlite3_mutex *p){
#if defined(SQLITE_DEBUG) || defined(SQLITE_TEST)
DWORD tid = GetCurrentThreadId();
#endif
#ifdef SQLITE_DEBUG
assert( p );
assert( p->id==SQLITE_MUTEX_RECURSIVE || winMutexNotheld2(p, tid) );
#else
assert( p );
#endif
assert( winMutex_isInit==1 );
EnterCriticalSection(&p->mutex);
#ifdef SQLITE_DEBUG
assert( p->nRef>0 || p->owner==0 );
p->owner = tid;
p->nRef++;
if( p->trace ){
OSTRACE(("ENTER-MUTEX tid=%lu, mutex(%d)=%p (%d), nRef=%d\n",
tid, p->id, p, p->trace, p->nRef));
}
#endif
}
static int winMutexTry(sqlite3_mutex *p){
#if defined(SQLITE_DEBUG) || defined(SQLITE_TEST)
DWORD tid = GetCurrentThreadId();
#endif
int rc = SQLITE_BUSY;
assert( p );
assert( p->id==SQLITE_MUTEX_RECURSIVE || winMutexNotheld2(p, tid) );
/*
** The sqlite3_mutex_try() routine is very rarely used, and when it
** is used it is merely an optimization. So it is OK for it to always
** fail.
**
** The TryEnterCriticalSection() interface is only available on WinNT.
** And some windows compilers complain if you try to use it without
** first doing some #defines that prevent SQLite from building on Win98.
** For that reason, we will omit this optimization for now. See
** ticket #2685.
*/
#if defined(_WIN32_WINNT) && _WIN32_WINNT >= 0x0400
assert( winMutex_isInit==1 );
assert( winMutex_isNt>=-1 && winMutex_isNt<=1 );
if( winMutex_isNt<0 ){
winMutex_isNt = sqlite3_win32_is_nt();
}
assert( winMutex_isNt==0 || winMutex_isNt==1 );
if( winMutex_isNt && TryEnterCriticalSection(&p->mutex) ){
#ifdef SQLITE_DEBUG
p->owner = tid;
p->nRef++;
#endif
rc = SQLITE_OK;
}
#else
UNUSED_PARAMETER(p);
#endif
#ifdef SQLITE_DEBUG
if( p->trace ){
OSTRACE(("TRY-MUTEX tid=%lu, mutex(%d)=%p (%d), owner=%lu, nRef=%d, rc=%s\n",
tid, p->id, p, p->trace, p->owner, p->nRef, sqlite3ErrName(rc)));
}
#endif
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 or
** is not currently allocated. SQLite will never do either.
*/
static void winMutexLeave(sqlite3_mutex *p){
#if defined(SQLITE_DEBUG) || defined(SQLITE_TEST)
DWORD tid = GetCurrentThreadId();
#endif
assert( p );
#ifdef SQLITE_DEBUG
assert( p->nRef>0 );
assert( p->owner==tid );
p->nRef--;
if( p->nRef==0 ) p->owner = 0;
assert( p->nRef==0 || p->id==SQLITE_MUTEX_RECURSIVE );
#endif
assert( winMutex_isInit==1 );
LeaveCriticalSection(&p->mutex);
#ifdef SQLITE_DEBUG
if( p->trace ){
OSTRACE(("LEAVE-MUTEX tid=%lu, mutex(%d)=%p (%d), nRef=%d\n",
tid, p->id, p, p->trace, p->nRef));
}
#endif
}
sqlite3_mutex_methods const *sqlite3DefaultMutex(void){
static const sqlite3_mutex_methods sMutex = {
winMutexInit,
winMutexEnd,
winMutexAlloc,
winMutexFree,
winMutexEnter,
winMutexTry,
winMutexLeave,
#ifdef SQLITE_DEBUG
winMutexHeld,
winMutexNotheld
#else
0,
0
#endif
};
return &sMutex;
}
#endif /* SQLITE_MUTEX_W32 */