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Overview
Comment:Added fix to os_win.c for race conditions from os_unix.c; added saving of errno in two places.
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SHA1:13ed106c8c279422a6159e28c6887d13a88b7b8b
User & Date: shaneh 2010-07-20 20:23:38
Original Comment: Added fix for race conditions from os_unix.c; added saving of errno in two places.
Context
2010-07-21
16:16
Version 3.7.0 check-in: b36b105e user: drh tags: trunk, release
2010-07-20
20:23
Added fix to os_win.c for race conditions from os_unix.c; added saving of errno in two places. check-in: 13ed106c user: shaneh tags: trunk
18:59
Fix a race condition in os_unix.c that may occur when one thread is opening a connection to a shared-memory block and another is either closing or locking the same shared-memory. check-in: 3b7330c1 user: dan tags: trunk
Changes
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Changes to src/os_win.c.

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**
** Function winShmMutexHeld() is used to assert() that the global mutex 
** is held when required. This function is only used as part of assert() 
** statements. e.g.
**
**   winShmEnterMutex()
**     assert( winShmMutexHeld() );
**   winEnterLeave()
*/
static void winShmEnterMutex(void){
  sqlite3_mutex_enter(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
}
static void winShmLeaveMutex(void){
  sqlite3_mutex_leave(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
}
................................................................................

  /* Release/Acquire the system-level lock */
  if( lockType==_SHM_UNLCK ){
    rc = UnlockFileEx(pFile->hFile.h, 0, nByte, 0, &ovlp);
  }else{
    rc = LockFileEx(pFile->hFile.h, dwFlags, 0, nByte, 0, &ovlp);
  }





  rc = (rc!=0) ? SQLITE_OK : SQLITE_BUSY;


  OSTRACE(("SHM-LOCK %d %s %s 0x%08lx\n", 
           pFile->hFile.h,
           rc==SQLITE_OK ? "ok" : "failed",
           lockType==_SHM_UNLCK ? "UnlockFileEx" : "LockFileEx",
           GetLastError()));

  return rc;
}

/* Forward references to VFS methods */
static int winOpen(sqlite3_vfs*,const char*,sqlite3_file*,int,int*);
static int winDelete(sqlite3_vfs *,const char*,int);
................................................................................
      rc = winShmSystemLock(pShmNode, _SHM_RDLCK, WIN_SHM_DMS, 1);
    }
    if( rc ) goto shm_open_err;
  }

  /* Make the new connection a child of the winShmNode */
  p->pShmNode = pShmNode;
  p->pNext = pShmNode->pFirst;
#ifdef SQLITE_DEBUG
  p->id = pShmNode->nextShmId++;
#endif
  pShmNode->pFirst = p;
  pShmNode->nRef++;
  pDbFd->pShm = p;
  winShmLeaveMutex();












  return SQLITE_OK;

  /* Jump here on any error */
shm_open_err:
  winShmSystemLock(pShmNode, _SHM_UNLCK, WIN_SHM_DMS, 1);
  winShmPurge(pDbFd->pVfs, 0);      /* This call frees pShmNode if required */
  sqlite3_free(p);
................................................................................
    );
#endif
  }
  OSTRACE(("OPEN %d %s 0x%lx %s\n", 
           h, zName, dwDesiredAccess, 
           h==INVALID_HANDLE_VALUE ? "failed" : "ok"));
  if( h==INVALID_HANDLE_VALUE ){

    free(zConverted);
    if( flags & SQLITE_OPEN_READWRITE ){
      return winOpen(pVfs, zName, id, 
             ((flags|SQLITE_OPEN_READONLY)&~SQLITE_OPEN_READWRITE), pOutFlags);
    }else{
      return SQLITE_CANTOPEN_BKPT;
    }







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**
** Function winShmMutexHeld() is used to assert() that the global mutex 
** is held when required. This function is only used as part of assert() 
** statements. e.g.
**
**   winShmEnterMutex()
**     assert( winShmMutexHeld() );
**   winShmLeaveMutex()
*/
static void winShmEnterMutex(void){
  sqlite3_mutex_enter(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
}
static void winShmLeaveMutex(void){
  sqlite3_mutex_leave(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
}
................................................................................

  /* Release/Acquire the system-level lock */
  if( lockType==_SHM_UNLCK ){
    rc = UnlockFileEx(pFile->hFile.h, 0, nByte, 0, &ovlp);
  }else{
    rc = LockFileEx(pFile->hFile.h, dwFlags, 0, nByte, 0, &ovlp);
  }
  
  if( rc!= 0 ){
    rc = SQLITE_OK;
  }else{
    pFile->lastErrno =  GetLastError();
    rc = SQLITE_BUSY;
  }

  OSTRACE(("SHM-LOCK %d %s %s 0x%08lx\n", 
           pFile->hFile.h,
           rc==SQLITE_OK ? "ok" : "failed",
           lockType==_SHM_UNLCK ? "UnlockFileEx" : "LockFileEx",
           pFile->lastErrno));

  return rc;
}

/* Forward references to VFS methods */
static int winOpen(sqlite3_vfs*,const char*,sqlite3_file*,int,int*);
static int winDelete(sqlite3_vfs *,const char*,int);
................................................................................
      rc = winShmSystemLock(pShmNode, _SHM_RDLCK, WIN_SHM_DMS, 1);
    }
    if( rc ) goto shm_open_err;
  }

  /* Make the new connection a child of the winShmNode */
  p->pShmNode = pShmNode;

#ifdef SQLITE_DEBUG
  p->id = pShmNode->nextShmId++;
#endif

  pShmNode->nRef++;
  pDbFd->pShm = p;
  winShmLeaveMutex();

  /* The reference count on pShmNode has already been incremented under
  ** the cover of the winShmEnterMutex() mutex and the pointer from the
  ** new (struct winShm) object to the pShmNode has been set. All that is
  ** left to do is to link the new object into the linked list starting
  ** at pShmNode->pFirst. This must be done while holding the pShmNode->mutex 
  ** mutex.
  */
  sqlite3_mutex_enter(pShmNode->mutex);
  p->pNext = pShmNode->pFirst;
  pShmNode->pFirst = p;
  sqlite3_mutex_leave(pShmNode->mutex);
  return SQLITE_OK;

  /* Jump here on any error */
shm_open_err:
  winShmSystemLock(pShmNode, _SHM_UNLCK, WIN_SHM_DMS, 1);
  winShmPurge(pDbFd->pVfs, 0);      /* This call frees pShmNode if required */
  sqlite3_free(p);
................................................................................
    );
#endif
  }
  OSTRACE(("OPEN %d %s 0x%lx %s\n", 
           h, zName, dwDesiredAccess, 
           h==INVALID_HANDLE_VALUE ? "failed" : "ok"));
  if( h==INVALID_HANDLE_VALUE ){
    pFile->lastErrno = GetLastError();
    free(zConverted);
    if( flags & SQLITE_OPEN_READWRITE ){
      return winOpen(pVfs, zName, id, 
             ((flags|SQLITE_OPEN_READONLY)&~SQLITE_OPEN_READWRITE), pOutFlags);
    }else{
      return SQLITE_CANTOPEN_BKPT;
    }