Programando con Hilos de Windows* Intel Software College.

Presentación del tema: "Programando con Hilos de Windows* Intel Software College."— Transcripción de la presentación:

1 Programando con Hilos de Windows* Intel Software College

2 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 2 Programming with Windows Threads Objetivos Al término de este módulo, será capaz de: Escribir programas para crear y terminar hilos Usar objetos de sincronización para coordinar la ejecución entre hilos y accesos a memoria

3 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 3 Programming with Windows Threads Agenda Explorar las funciones del API para hilos en Win32 Crear hilos Esperar que los hilos terminen Sincronizar acceso compartido entre hilos Prácticas para experiencia práctica

4 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 4 Programming with Windows Threads Windows* tipo HANDLE Cada objeto de windows es referenciado por variables de tipo HANDLE Apuntador a objetos del kernel Hilo, proceso, archivo, evento, mutex, semáforo, etc. Las funciones para crear objetos devuelven un HANDLE Los objetos se controlan a través de su HANDLE No se manipulan directamente los objetos

5 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 5 Programming with Windows Threads Creación de Hilos en Windows* HANDLE CreateThread( LPSECURITY_ATTRIBUTES ThreadAttributes, DWORD StackSize, LPTHREAD_START_ROUTINE StartAddress, LPVOID Parameter, DWORD CreationFlags, LPDWORD ThreadId ); // Out

6 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 6 Programming with Windows Threads LPTHREAD_START_ROUTINE CreateThread() espera un apuntador a una función global Devuelve DWORD Convención de llamadas de WINAPI Un solo parámetro LPVOID (void *) El hilo inicia la ejecución de la función DWORD WINAPI MyThreadStart(LPVOID p);

7 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 7 Programming with Windows Threads Usando Hilos Explícitamente Identifica porciones de código a paralelizar Encapsula código en una función Si el código ya es una función, una función de un driver puede necesitar ser escrita para coordinar el trabajo de varios hilos Añadir la llamada CreateThread para asignar hilos para ejecutar la función

8 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 8 Programming with Windows Threads Destruyendo Hilos Libera recursos del SO Limpia si se terminó el trabajo con el hilo antes de que el programa termine La terminación del proceso lo hace BOOL CloseHandle(HANDLE hObject);

9 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 9 Programming with Windows Threads Ejemplo: Creación de Hilos #include DWORD WINAPI helloFunc(LPVOID arg ) { printf(Hello Thread\n); return 0; } main() { HANDLE hThread = CreateThread(NULL, 0, helloFunc, NULL, 0, NULL ); } ¿Qué Sucede?

10 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 10 Programming with Windows Threads Explicación del Ejemplo El hilo principal es un proceso Cuando el proceso termina, todos los hilos terminan Se requiere algún método para esperar que un hilo termine

11 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 11 Programming with Windows Threads #include BOOL threadDone = FALSE ; DWORD WINAPI helloFunc(LPVOID arg ) { printf(Hello Thread\n); threadDone = TRUE ; return 0; } main() { HANDLE hThread = CreateThread(NULL, 0, helloFunc, NULL, 0, NULL ); while (!threadDone); } Esperando un Hilo de Windows* No es una buena idea! // ciclos desperdiciados!

12 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 12 Programming with Windows Threads Esperando un Hilo Espera un objeto (hilo) DWORD WaitForSingleObject( HANDLE hHandle, DWORD dwMilliseconds ); El hilo creador de hilos espera (bloqueado) hasta El tiempo expira Regresa un código para indicarlo El hilo sale (se le indica al manejador) Usa INFINITE para esperar hasta la terminación del hilo No usa ciclos del CPU

13 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 13 Programming with Windows Threads Esperando Muchos Hilos Espera hasta 64 objetos (hilos) DWORD WaitForMultipleObjects( DWORD nCount, CONST HANDLE *lpHandles, // arreglo BOOL fWaitAll, // espera uno o todos DWORD dwMilliseconds) Espera a todos: fWaitAll==TRUE Espera a cualquiera: fWaitAll==FALSE El valor de retorno es el primer índice del arreglo encontrado

14 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 14 Programming with Windows Threads Detalles en las funciones WaitFor* Descriptor (Handle) como parámetro Usado para diferentes tipos de objetos Los objetos del kernel tienen dos estados Signaled Non-signaled El comportamiento se define por el objeto referido por el manejador Hilo: signaled indica terminado

15 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 15 Programming with Windows Threads Ejemplo: Varios Hilos #include const int numThreads = 4; DWORD WINAPI helloFunc(LPVOID arg ) { printf(Hello Thread\n); return 0; } main() { HANDLE hThread[numThreads]; for (int i = 0; i < numThreads; i++) hThread[i] = CreateThread(NULL, 0, helloFunc, NULL, 0, NULL ); WaitForMultipleObjects(numThreads, hThread, TRUE, INFINITE); }

16 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 16 Programming with Windows Threads Activdad 1 - HelloThreads Modifica el ejemplo previo para para mostrar El mensaje Hello Thread apropiaido Número de hilo único Usa el la variable del ciclo for del CreateThread Salida ejemplo: Hello from Thread #0 Hello from Thread #1 Hello from Thread #2 Hello from Thread #3

17 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 17 Programming with Windows Threads ¿Qué es Incorrecto? ¿Qué se muestra en myNum? DWORD WINAPI threadFunc(LPVOID ) { DWORD WINAPI threadFunc(LPVOID pArg) { int* p = (int*)pArg; int* p = (int*)pArg; int myNum = *p; printf( Thread number %d\n, myNum);}... // from main(): for (int i = 0; i < numThreads; i++) { hThread[i] = hThread[i] = CreateThread(NULL, 0, threadFunc, &i, 0, NULL); CreateThread(NULL, 0, threadFunc, &i, 0, NULL);}

18 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 18 Programming with Windows Threads for(int i=0;i<numThreads;i++) { CreateThread(NULL, 0, threadFunc, &i, 0, NULL); } DWORD WINAPI threadFunc(LPVOID ) { DWORD WINAPI threadFunc(LPVOID pArg) { int* p = (int*)pArg; int* p = (int*)pArg; int myNum = *p; printf( Thread number %d\n, myNum);} i=0x0001004 pArg=0x0001008 p=0x000100C mynum=0x0001010 0 0x0001004 1 1 1 Contenido de la dirección 0x0001004

19 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 19 Programming with Windows Threads Línea de Tiempo Hello Threads TiempomainThread 0Thread 1 T0T0 i = 0------- T1T1 create(&i)--- T2T2 i++ (i == 1)launch--- T3T3 create(&i)p = pArg--- T4T4 i++ (i == 2)myNum = *p myNum = 2 launch T5T5 waitprint(2)p = pArg T6T6 waitexitmyNum = *p myNum = 2

20 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 20 Programming with Windows Threads Condiciones de Concurso Varios hilos acceden la misma variable de manera concurrente Conflicto Lectura/Escritura Conflicto Escritura/Escritura El error más común en programas concurrentes No siempre es obvio

21 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 21 Programming with Windows Threads ¿Cómo Evitar Condiciones de Concurso? El alcance de las variables local en los hilos Variables declaradas dentro de las funciones de los hilos Se almacenan en el stack del hilo TLS (Thread Local Storage) Controla el acceso compartido con regiones críticas Exclusión mutua y sincronización Lock, semáforo, evento, sección crítica, mutex …

22 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 22 Programming with Windows Threads Solución – Almacenamiento Local DWORD WINAPI threadFunc(LPVOID ) DWORD WINAPI threadFunc(LPVOID pArg){ (int*)pArg) int myNum = *((int*)pArg); printf( Thread number %d\n, myNum);}... // from main(): for (int i = 0; i < numThreads; i++) { tNum[i] = i; tNum[i] = i; hThread[i] = hThread[i] = CreateThread(NULL, 0, threadFunc, &tNum[i], CreateThread(NULL, 0, threadFunc, &tNum[i], 0, NULL); 0, NULL);}

23 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 23 Programming with Windows Threads Windows* Mutexes Objeto del kérnel que se referencía por un descriptor Signaled cuando está disponible Operaciones: CreateMutex(…) // crear nuevo WaitForSingleObject // wait y lock ReleaseMutex(…) // unlock Disponible entre procesos

24 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 24 Programming with Windows Threads Sección Crítica en Windows* Ligero, entre procesos solo mutex El más útil y más usado Nuevo tipo CRITICAL_SECTION cs; Operaciones de crear y destruir InitializeCriticalSection(&cs) DeleteCriticalSection(&cs);

25 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 25 Programming with Windows Threads Sección Crítica en Windows* CRITICAL_SECTION cs ; Intenta entrar al código protegido EnterCriticalSection(&cs) Se bloquea si otro hilo está en la sección crítica Regresa cuando no hay hilos en la sección crítica Al salir de la sección crítica LeaveCriticalSection(&cs) Debe ser desde el hilo que la obtiene

26 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 26 Programming with Windows Threads Ejemplo: Sección Crítica #define NUMTHREADS 4 CRITICAL_SECTION g_cs; // ¿Por qué tiene que ser global? int g_sum = 0; DWORD WINAPI threadFunc(LPVOID arg ) { int mySum = bigComputation(); EnterCriticalSection(&g_cs); g_sum += mySum;// Los hilos acceden una a la vez LeaveCriticalSection(&g_cs); return 0; } main() { HANDLE hThread[NUMTHREADS]; InitializeCriticalSection(&g_cs); for (int i = 0; i < NUMTHREADS; i++) hThread[i] = CreateThread(NULL,0,threadFunc,NULL,0,NULL); WaitForMultipleObjects(NUMTHREADS, hThread, TRUE, INFINITE); DeleteCriticalSection(&g_cs); }

27 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 27 Programming with Windows Threads Ejemplo de Integración Numérica 4.0 2.0 1.0 0.0 4.0 (1+x 2 ) f(x) = 4.0 (1+x 2 ) dx = 0 1 X static long num_steps=100000; double step, pi; void main() { int i; double x, sum = 0.0; step = 1.0/(double) num_steps; for (i=0; i< num_steps; i++){ x = (i+0.5)*step; sum = sum + 4.0/(1.0 + x*x); } pi = step * sum; printf(Pi = %f\n,pi); }

28 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 28 Programming with Windows Threads Actividad 2 - Calculando Pi Paraleliza la integración numérica usando hilos de Windows* Como pueden las iteraciones de los ciclos dividirse entre los hilos ¿Qué variables pueden ser locales? ¿Qué variables necesitan ser visibles a todos los hilos? static long num_steps=100000; double step, pi; void main() { int i; double x, sum = 0.0; step = 1.0/(double) num_steps; for (i=0; i< num_steps; i++){ x = (i+0.5)*step; sum = sum + 4.0/(1.0 + x*x); } pi = step * sum; printf(Pi = %f\n,pi);}

29 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 29 Programming with Windows Threads Eventos de Windows* Usados para enviarle a otros hilos señales de que ha ocurrido un evento Ejemplo: los datos están disponibles, el mensaje está listo Los hilos esperan señales con la función WaitFor * Dos tipos de eventos Auto-reset Manual-reset

30 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 30 Programming with Windows Threads Tipos de Eventos El sistema automáticamente resetea el evento al estado non-signaled después de que un hilo es liberado El evento permanece en estado signaled y requiere que una función ResetEvent establezca el estado del evento a non- signaled. Precaución: Sea cuidadoso cuando se usa WaitForMultipleObjects para esperar TODOS los eventos Manual-resetAuto-reset

31 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 31 Programming with Windows Threads Creación de Eventos en Windows* HANDLE CreateEvent( LPSECURITY_ATTRIBUTES lpEventAttributes, BOOL bManualReset, // TRUE => manual reset BOOL bInitialState, // TRUE => begin signaled LPCSTR lpName); // text name for object Establecer bManualReset a TRUE para un evento manual-reset event; FALSE para un evento auto-reset Establecer bInitialState a TRUE para que un evento inicie en estado signaled; FALSE para iniciar unsignaled

32 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 32 Programming with Windows Threads Establecer y Reiniciar Eventos Establecer un evento a un estado signaled BOOL SetEvent( HANDLE event ); Reiniciar un evento manualmente BOOL ResetEvent( HANDLE event ); Pulsar evento BOOL PulseEvent( HANDLE event );

33 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 33 Programming with Windows Threads Ejemplo: Un Hilo Buscador Un hilo creado busca un elemento Manda una señal si el elemento se encuentra El hilo principal (Main Thread) espera la señal y terminación del hilo Muestra un mensaje si el elemento se encuentra Muestra mensaje hasta la terminación del hilo Ilustra Usando el tipo HANDLE genérico No esperar que cada objeto haga un signal

34 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 34 Programming with Windows Threads Eejemplo: Eventos DWORD WINAPI threadFunc(LPVOID arg) { BOOL bFound = bigFind() ; if (bFound) { SetEvent(hObj[0]); // señal, el dato fue encontrado bigFound() ; } moreBigStuff() ; return 0; } HANDLE hObj[2]; // 0 es evento, 1 es hilo

35 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 35 Programming with Windows Threads Ejempo: Función Principal... hObj[0] = CreateEvent(NULL, FALSE, FALSE, NULL); hObj[1] = CreateThread(NULL,0,threadFunc,NULL,0,NULL); /* Hacer otra cosa mientras el hilo realiza la búsqueda */ DWORD waitRet = WaitForMultipleObjects(2, hObj, FALSE, INFINITE); switch(waitRet) { case WAIT_OBJECT_0: // señal del evento printf("found it!\n"); WaitForSingleObject(hObj[1], INFINITE) ; // case WAIT_OBJECT_0+1:// señal del hilo printf("thread done\n"); break ; default: printf("wait error: ret %u\n", waitRet); break ; }...

36 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 36 Programming with Windows Threads Ejempo: Función Principal... hObj[0] = CreateEvent(NULL, FALSE, FALSE, NULL); hObj[1] = CreateThread(NULL,0,threadFunc,NULL,0,NULL); /* Do some other work while thread executes search */ DWORD waitRet = WaitForMultipleObjects(2, hObj, FALSE, INFINITE); switch(waitRet) { case WAIT_OBJECT_0: // señal del evento printf(encontrado!\n"); WaitForSingleObject(hObj[1], INFINITE) ; // fall thru case WAIT_OBJECT_0+1:// señal del hilo printf(hilo terminado\n"); break ; default: printf("wait error: ret %u\n", waitRet); break ; }...

37 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 37 Programming with Windows Threads Actividad 3 – Usando Eventos Remplazar el spin-wait y la variable contador de hilos con eventos para enviar señal de terminación de hilo de la pieza computacional

38 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 38 Programming with Windows Threads Semáforos de Windows* Objetos de sincronización que contienen un contador Representa el número de recursos disponibles Formalizados por Edsger Dijkstra (1968) Dos operaciones en los semáforos Wait [P(s)]: El hilo espera hasta que s > 0, entonces s = s-1 Post [V(s)]: s = s + 1 El semáforo está en estado signaled si el contador > 0

39 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 39 Programming with Windows Threads Win32* Creación de Semáforos HANDLE CreateSemaphore( LPSECURITY_ATTRIBUTES lpEventAttributes, LONG lSemInitial, // Initial count value LONG lSemMax, // Maximum value for count LPCSTR lpSemName); // text name for object Valor de lSemMax debe ser 1 o mayor Valor de lSemInitial debe ser Mayor o igual a cero, Menor o igual que lSemMax, y No puede estar fuera del rango

40 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 40 Programming with Windows Threads Operaciones Wait y Post Usa WaitForSingleObject para esperar en un semáforo Si el contador es == 0, el hilo espera Decrementa el contador en 1 cuando el contador > 0 Incrementa el semáforo (Operación Post) BOOL ReleaseSemaphore( HANDLE hSemaphore, LONG cReleaseCount, LPLONG lpPreviousCount ); Incrementa el contador del semáforo según el valor de cReleaseCount Devuelve el valor previo del contador a través de lpPreviousCount

41 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 41 Programming with Windows Threads Aplicaciones de los Semáforos Controlar el acceso a estructuras de datos de tamaño limitado Colas, stacks, deques Usa un contador para enumerar elementos disponibles Controla el acceso a un número finito de recursos Descriptores de archivos, unidades de cinta, … Regula la cantidad de hilos activos dentro de una región Un semáforo binario [0,1] puede funcionar como un mutex

42 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 42 Programming with Windows Threads Cuidados con el uso de Semáforos No hay propietario del semáforo Cualquier hilo puede liberar un semáforo, no solo el ultimo hilo que realizó el wait Usar una buena práctica de programación para evitar esto No existe el concepto de semáforo abandonado Si el hilo termina antes de realizar la operación post, se pierde el incremento del semáforo Deadlock

43 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 43 Programming with Windows Threads Ejemplo: Semáforo como Mutex El hilo principal abre el archivo de entrada, espera la terminación del hilo Los hilos Leen la línea del archivo de entrada Cuentan todas las palabras de cinco letras en una línea

44 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 44 Programming with Windows Threads Ejemplo: Principal main() { HANDLE hThread[NUMTHREADS]; hSem1 = CreateSemaphore(NULL, 1, 1, NULL); // Binary semaphore hSem2 = CreateSemaphore(NULL, 1, 1, NULL); // Binary semaphore fd = fopen(InFile, r); // Open file for read for (int i = 0; i < NUMTHREADS; i++) hThread[i] = CreateThread(NULL,0,CountFives,NULL,0,NULL); WaitForMultipleObjects(NUMTHREADS, hThread, TRUE, INFINITE); fclose(fd); printf(Number of five letter words is %d\n, fiveLetterCount); } HANDLE hSem1, hSem2; FILE *fd; int fiveLetterCount = 0;

45 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 45 Programming with Windows Threads Ejemplo: Semáforos DWORD WINAPI CountFives(LPVOID arg) { BOOL bDone = FALSE ; char inLine[132]; int lCount = 0; while (!bDone) { WaitForSingleObject(hSem1, INFINITE); // accede la entrada bDone = (GetNextLine(fd, inLine) == EOF); ReleaseSemaphore(hSem1, 1, NULL); if (!bDone) if (lCount = GetFiveLetterWordCount(inLine)) { WaitForSingleObject(hSem2, INFINITE);//actualiza var fiveLetterCount += lCount; ReleaseSemaphore(hsem2, 1, NULL); }

46 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 46 Programming with Windows Threads Actividad 4 – Usando Semáforos Usar semáforos binarios para controlar el acceso a variables compartidas

47 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 47 Programming with Windows Threads Programando con Hilos de Windows Que se ha Cubierto Crear hilos para ejecutar trabajo encapsulado dentro de funciones Lo normal de esperar hilos para terminar Coordinar acceso compartido entre hilos para evitar condiciones de concurso Almacenamiento local para evitar concursos Objetos de sincronización para organizar el uso

48 Copyright © 2006, Intel Corporation. All rights reserved. Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States or other countries. *Other brands and names are the property of their respective owners. 48 Programming with Windows Threads