Lecture 6 : Multitasking & DLL

Size: px

Start display at page:

Download "Lecture 6 : Multitasking & DLL"

Alban King
5 years ago
Views:

1 Lecture 6 : Multitasking & DLL Multitask CreadThread, ExitThread, TerminateThread beginthreadex, endthreadex : memory leak SuspendThread, ResumeThread Sleep Thread priorities Synchronization CreateSemaphore, WaitForSingleObject, ReleaseSemaphore DLL Static library work vs Dynamic library work Load-time, Run-time How to create DLL How to use DLL 1

2 Part I :Multitasking Windows application can consist of more than one process (a program) A process can consist of more than one thread Win 32 API support multitasking Create the effect of simultaneous execution of multiple processes and threads Focus on multi-thread a process consist of more than one thread 2

3 Threads Concept Multiple threads on multiple CPUs Multiple threads sharing a single CPU Thread 1 Thread 2 Thread 3 Thread 1 Thread 2 Thread 3 3

4 thread1 thread 2 Multitasking (cont.) A multitasking operating system divides the available CPU time among the threads that need it. In windows, the Win 32 API is designed for preemptive multitasking Means the system allocates small slices of CPU time among the competing threads Currently executing thread is suspended when its time slice elapses (20 ms.) single processor system Advantage of multitasking To the user Ability to have several applications open and working at the same time. Ex: A user can edit a file with one app while another app is printing a spreadsheet To the application developer Ability to create app that to create a process that use more than one thread of execution ex. One thread for handling interactions with the user while other threads with low priority perform the other work of the process 4

5 Creating a Thread To create a thread, use th API function CreateThread() HANDLE CreateThread( LPSECURITY_ATTRIBUTES lpthreadattributes, // pointer to security attributes DWORD dwstacksize, // initial thread stack size LPTHREAD_START_ROUTINE lpstartaddress, // pointer to thread function LPVOID lpparameter, // Pointer to a variable to be passed to the thread DWORD dwcreationflags, // creation flags LPDWORD lpthreadid // pointer to receive thread ID ); A thread of execution terminates when its entry function returns DWORD WINAPI ThreadProc( LPVOID lpparameter); ThreadProc เป นช ออะไรก ได 5

6 Creating a Thread Parameters 1: NULL to get the default security descriptor 2: the size of the new thread s stack, in bytes, common approach 0 3: thread function: DWORD WINAPI ThreadProc( LPVOID lpparameter); 4: any argument that needs to pass to the new thread (lpparameter) 5: the execution state of the thread 0 : begin execution immediately CREATE_SUSPENDED : awaiting execution, Call to ResumeThread() function 6: identifier associated with a thread Thread ID If successful the function returns a handle to the thread If failure returns NULL Hthread1 = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)MyThread1, (LPVOID) hwnd, 0, &Tid1) ; DWORD WINAPI MyThread1(LPVOID param) {..} 6

7 Thread s Life cycle Blocked ResumeThread() new Ready scheduler Running t1=createthread( p1,p2,p3,p4,0,p6) Fn.thread return t1=createthread( p1,p2,p3,p4, CREATE_SUSPENDED,p6) Finished 7

8 DWORD Tid; LRESULT CALLBACK WindowProc(HWND hwnd, UINT message, WPARAM wparam, LPARAM lparam) { HANDLE hthread; int response; } switch(message) { case WM_COMMAND: switch(loword(wparam)) { case IDM_THREAD: /* เมส ไว ส าหร บสร าง Thread create the threads */ hthread = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)MyThread1, break; Demo Program :ThreadEx1 threadex1 (LPVOID)hwnd, 0, &Tid1); DWORD WINAPI MyThread1(LPVOID param) { } int i; HDC hdc; for(i=0; i<max; i++) { } sprintf(str, "Thread 1: loop # %5d ", i); hdc = GetDC((HWND) param);// ใช พาราม เตอร ท ส งมา TextOut(hdc, 1, 1, str, strlen(str)); ReleaseDC((HWND) param, hdc); return 0; 8

9 Terminating a Thread Terminate the thread manually BOOL TerminateThread(HANDLE hthread,dword dwexitcode); May stop a thread during an important operation Does not perform any special cleanup activities For example, TerminateThread can result in the following problems: If the target thread owns a critical section, the critical section will not be released. If the target thread is allocating memory from the heap, the heap lock will not be released. Return values Nonzero success Zero fail VOID ExitThread(DWORD dwexitcode); Stack is properly reset : return normally 9

10 Alternatives to CreateThread() and ExitThread() If a multithreaded program utilizes standard C library functions (sprintf, strlen, etc.) Use of the CreateThread() and ExitThread() causes small memory leaks ม ว ธ แก 2 ว ธ ค อ ใช CreateThread() & ExitThread() ของ win 32 ก บ functionท ท างานเหม อน standard C library fn. ของ win 32 ใช C runtime library to start และ stop thread แทนการ ใช CreateThread() & ExitThread() 10

11 ว ธ ท หน ง: Avoiding the C Library Functions Still use a function CreateThread(), ExitThread() Win 32 contains substitutes for several C string handling functions wsprintf(), lstrlen(), lstrcat(), lstrcpy(), CharUpper(), CharLower(), IsCharAlpha(), IsCharAlphaNumeric(), etc. 11

12 ว ธ ท สอง:Using C runtime library using C runtime library to start and stop thread _beginthreadex() and endthreadex() #include <process.h> setting a project property to be multi-threaded debug _beginthreadex(null, 0, MyThread1,(LPVOID) hwnd, 0,(unsigned *) &Tid1); #include <process.h>... unsigned _stdcall MyThread1(void * param) { TextOut(hdc, 250, 180, str, strlen(str)); ReleaseDC((HWND) param, hdc); } return 0; } Demo Program: ThreadEx2 เป ดโปรเจ ค 12

13 Project [ThreadEx2]Properties.. Visual 2005 จะเป น default ให แต Visual 2003 ต องมาเซ ตเอง 13

14 Suspending and Resuming a Thread DWORD SuspendThread(HANDLE hthread); DWORD ResumeThread(HANDLE hthread); hthread is a returned value of function CreateThread() VOID Sleep(DWORD Duration // length of time, in milliseconds); ไว ในฟ งก ช นของ Thread hthread = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)MyThread1, (LPVOID)hwnd, 0, &Tid1); 5 th Parameter :CREATE_SUSPENDED 14

15 Thread s Life cycle Time out ResumeThread() Blocked Sleep() SuspendThread() new Ready Running scheduler t1=createthread( p1,p2,p3,p4,0,p6) Fn.thread return Finished 15

16 Thread Priorities A thread s priority determines how much CPU time a thread receives Low-priority threads receive little High-priority threads receive a lot A thread s priority setting is the combination of two values: The overall priority class of the process and The priority setting of the individual thread relative to that priority class BOOL SetThreadPriority( HANDLE hthread, // handle to the thread int npriority // thread priority level ); int GetThreadPriority( HANDLE hthread // handle to thread ); 16

17 SetThreadPriority(HANDLE hthread, int npriority ) Priority Meaning THREAD_PRIORITY_ABOVE_NORMAL Priority 1 point above the priority class THREAD_PRIORITY_BELOW_NORMAL Priority 1 point below the priority class THREAD_PRIORITY_HIGHEST Priority 2 points above the priority class THREAD_PRIORITY_LOWEST Priority 2 points below the priority class. THREAD_PRIORITY_NORMAL Normal priority for the priority class. link DWORD GetPriorityClass( HANDLE hprocess ); ร บค า priority ของ process 17

18 Synchronization When using multiple threads, it is sometimes necessary to coordinate the activities of two or more. This process is called synchronization The most common reason for this is when two or more threads need access to a shared resource One thread is writing a file A second thread must be prevented from doing so at the same time There are two general states that a task may be in: Executing ( or ready to execute as soon as it obtain its time slice) Blocked, awaiting some resource, in which case its execution is suspended until the needed resource is available 18

19 Semaphore File File is is not in in use. use. Thread Write a file File Thread Read a file 19

20 Using a Semaphore to Synchronize Threads HANDLE CreateSemaphore( LPSECURITY_ATTRIBUTES lpsemaphoreattributes, // pointer to //security attributes, NULL LONG linitialcount, //ม ท ว างส าหร บเทรดก ท 0 linitialcount lmaximumcount LONG lmaximumcount, // maximum count,ร นพร อมๆ ก นได ก เทรด lmaximumcount 0 LPCTSTR lpname // pointer to semaphore-object name ); DWORD WaitForSingleObject( HANDLE hhandle, // handle to semaphore object to wait for DWORD dwmilliseconds // time-out interval in milliseconds ); BOOL ReleaseSemaphore( HANDLE hsemaphore, // handle to the semaphore object LONG lreleasecount, // amount to add to current count LPLONG lppreviouscount // address of previous count,null ); ย งคงใช ค าส ง CreateThread() เหม อนเด ม Demo: Semaphore 20

21 Using a Semaphore to Control Resource :MyThread1, MyThread2 Count = 1 Initialize Semaphore Resource status Thread1 be in use Count = 0 Thread2 wait on Semaphore Handle Thread2 release Semaphore Thread2 be in use Count = 0 Thread1 release Semaphore Count = 1 Resource status Available for Thread2 21

22 HANDLE hsema; LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wparam, LPARAM lparam) { switch (message) {... case WM_CREATE: hsema = CreateSemaphore(NULL, 1, 1, NULL);// case WM_COMMAND: wmid = LOWORD(wParam); // Parse the menu selections: switch (wmid) { case IDM_THREAD: break; CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)MyThread1, (LPVOID)hWnd, 0, &Tid1); CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)MyThread2, (LPVOID)hWnd, 0, &Tid2); } break; Create a Semaphore 22

23 DWORD WINAPI MyThread1(LPVOID param) { int i; HDC hdc; // wait for access to be granted if (WaitForSingleObject(hSema, INTERVAL) == WAIT_TIMEOUT) { MessageBox((HWND)param, "Time out Thread 1", "Semaphore Error", MB_OK); return 0; } for (i = 0; i < MAX; i++) { if (i == MAX/2) { // Release at half way point. This allows MyThread2 to run ReleaseSemaphore(hSema, 1, NULL);... } 23

24 DWORD WINAPI MyThread2(LPVOID param) { char str[255]; int i; HDC hdc; // wait for access to be granted if (WaitForSingleObject(hSema, INTERVAL) == WAIT_TIMEOUT){ MessageBox((HWND)param, "Time out Thread 2 ", "Semaphore Error", MB_OK); return 0; } for (i = 0; i < MAX; i++){ wsprintf(str, "Thread 2 : loop # %5d ", i); hdc = GetDC((HWND)param); TextOut(hdc, 1, 20, str, lstrlen(str)); ReleaseDC((HWND)param, hdc); } ReleaseSemaphore(hSema, 1, NULL); return 0; }/ Semaphore1_1.exe ด ไฟล semaphore.pdf 24

$C:\Program Files\Microsoft Visual Studio 8$

25 C:\Program Files\Microsoft Visual Studio 8 \Common7\Tools\Bin\winnt\pview.exe link 25

26 Part II : Creating DLLs How does Static Library work? Static Library Copy added to each program during linking Library function ProgramA.exe ProgramB.exe ProgramC.exe Library function Library function Library function 26

27 How DLLsWork: Load-time Dynamic Linking 4.ProgramB loaded 1.ProgramA loaded Library.dll ProgramC.exe ProgramB.exe ProgramA.exe 2.DLL loaded 6.ProgramC loaded ProgramA ProgramB ProgramC Library.dll 5. Linkage to DLL function Library function 3.Linkage to DLL function 7. Linkage to DLL function Computer Memory 27

28 How DLLsWork: Run-time Dynamic Linking Library1.dll Library2.dll 3.Library2.dll loaded at the request of the program. 1.ProgramA loaded but no DLL is loaded. The program may use any one of three DLLs. Library3.dll Program.exe Program 2. At this point the program Determines that Library2.dll is required and causes it to be loaded. 4. The program obtains the address of a function from the DLL and uses it to call the function Library2.dll Library function Computer Memory 28

29 Creating DLLs Why? Placing functions in a DLL reduces the size of each component because the functions are not duplicated in each program Using DLLs makes upgrades easier Only the DLL file must be recompiled DLL Basics Any function contained in a DLL that will be called by code outside the DLL must be exported (use dllexport keyword) To use a function contained in a DLL, u must import (use dllimport keyword) it 29

30 Creating a DLL The dllexport and dllimport keywords cannot be used by themselves They need to be preceded by keyword: _declspec(specifier) Ex: Creating a DLL _declspec(dllexport) void MyFunc(int a) { } สร างเป น macro name #define DllExport _declspec (dllexport)... DllExport void MyFuncOne(int a){ } DllExport void MyFuncTwo(){ } If yr Dll is compiled as a C++ program, u want it to also be usable by C program #define DllExport extern C _declspec (dllexport) ต องใช C พ มพ ใหญ 30

31 Creating a DLL 31

32 Select DLL & Empty project 32

33 Project Add NewItem.. 33

34 Creating a Simple DLL Mydll.cpp #include <windows.h> #include <cstring> #define DllExport extern "C" _declspec (dllexport) /* This function displays the coordinates of the mouse at the point at which a mouse button was pressed. hdc: Specifies the device context in which to output the coordinates. lparam: Specifies the value of lparam when the button was pressed. */ DllExport void ShowMouseLoc(HDC hdc, LPARAM lparam) { char str[80]; wsprintf(str, "Button is down at %d, %d", LOWORD(lParam), HIWORD(lParam)); TextOut(hdc, LOWORD(lParam), HIWORD(lParam),str, strlen(str)); } Create a c++ file(*.cpp) that contains some functions to be a DLL. 34

35 Next Step Build DLL, can not run! If success u will get a *.dll & *.lib files in the directory Debug.dll file will contain the code for the functions that will be dynamically linked.lib file contains loading information that must be linked with any application that uses the library (during compile need this file) Open project :MyDll 35

36 Using the DLL :Load-time Dynamic Linking #include <windows.h> #include <cstring> #include testmydll.h // import dll s function LRESULT CALLBACK WindowFunc(HWND, UINT, WPARAM, LPARAM); char szwinname[] = "MyWin"; // name of window class testmydll.cpp int WINAPI WinMain(HINSTANCE hthisinst, HINSTANCE hprevinst, LPSTR lpszargs, int nwinmode) { } LRESULT CALLBACK WindowProc(HWND hwnd, UINT message, WPARAM wparam, LPARAM lparam) { HDC hdc; switch(message) { case WM_RBUTTONDOWN: // process right button hdc = GetDC(hwnd); // get DC ShowMouseLoc(hdc, lparam); // call DLL function ReleaseDC(hwnd, hdc); // Release DC break; case WM_LBUTTONDOWN: // process left button hdc = GetDC(hwnd); // get DC ShowMouseLoc(hdc, lparam); // call DLL function ReleaseDC(hwnd, hdc); // Release DC break; case WM_DESTROY: // terminate the program PostQuitMessage(0); break; default: return DefWindowProc(hwnd, message, wparam, lparam); } return 0; } 36

37 --Header file --Implement a DLL testmydll.h file #define DllImport extern "C" _declspec (dllimport) DllImport void ShowMouseLoc(HDC hdc, LPARAM lparm); เป นการบ งบอกว าจะ import function อะไรจาก dll เข ามาใน application การจ ดสภาพแวดล อมของ app ท เร ยกใช dll During development an application using a dll Two files ; *.dll, *.lib ; contains in the directory of the application Project AddExisting item ส าหร บไฟล.lib After that we need only.dll file to carry with *.exe file Demo Project: TestMyDll 37

38 Run-time Dynamic Linking Most often, when you use functions defined in a DLL, yr program calls those functions by name in its source code. Ex.. ShowMouseLoc() For this case, the Dll that contains the function is loaded when the application is loaded called loadtime dynamic linking (เป นว ธ ในสไลด ท กล าวมาแล ว) It is possible to load dynamic link libraries at runtime called run-time dynamic linking Yr program must manually load the Dll and then obtain pointers to the function that it wishes to use 38

39 Run-time Dynamic Linking At the core of run-time dynamic linking are these three functions: HMODULE LoadLibrary(LPCTSTR lpfilename); Loads the DLL specified by lpfilename and returns a handle to it FARPROC GetProcAddress( HMODULE hmodule, LPCSTR lpprocname ); Returns a pointer to the function named by lpprocname that is contained in the DLL specified by hmodule lpprocname must match exactly the name specified within the DLL BOOL FreeLibrary( HMODULE hmodule ); Frees the DLL when it is no longer needed hlib = LoadLibrary("MYDLL.DLL"); void (*f)(hdc, LPARAM); // get pointer to ShowMouseLoc f = (void (*)(HDC, LPARAM)) GetProcAddress(hlib, "ShowMouseLoc"); // call ShowMouseLoc (*f)(hdc, lparam); FreeLibrary(hlib); Demo Program : UsingLoadLibrary 39

$C:\Program Files\Microsoft Visual Studio$

40 C:\Program Files\Microsoft Visual Studio 8 \Common7\Tools\Bin\Depends.Exe link 40

Multi-core Architecture and Programming

Multi-core Architecture and Programming Yang Quansheng( 杨全胜 ) http://www.njyangqs.com School of Computer Science & Engineering 1 http://www.njyangqs.com Programming with Windows Threads Content Windows