Programando con Hilos POSIX* Intel Software College.
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Transcript of Programando con Hilos POSIX* Intel Software College.
Programando con Hilos POSIX*
Intel Software College
2
Copyright © 2006, Intel Corporation. All rights reserved.
Programming with POSIX* Threads
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.
Objetivos
Explorar las funciones de la librería Pthreads para crear y sincronizar hilos
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Copyright © 2006, Intel Corporation. All rights reserved.
Programming with POSIX* Threads
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.
¿Qué son los pthreads?
Estándar POSIX.1c
Interfaz en lenguaje C
Los hilos existen dentro del mismo proceso
Todos los hilos son pares
• No es un modelo explícito padre-hijo
• Excepto: “main thread” contiene toda la información del proceso
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Copyright © 2006, Intel Corporation. All rights reserved.
Programming with POSIX* Threads
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.
pthread_create
int pthread_create(tid, attr, function, arg);
pthread_t *tid• descriptor del hilo creado
const pthread_attr_t *attr• atributos del hilo a crearse
void *(*function)(void *)• función que será mapeada al hilo
void *arg• argumento que se envía a la función
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Copyright © 2006, Intel Corporation. All rights reserved.
Programming with POSIX* Threads
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.
pthread_create Detalles
Inicia un hilo ejecutando la función
Descriptor del hilo retornado por medio de la estructura pthread_t
• Especifica NULL para usar los atributos por default
Un solo argumento enviado a la función
• Si no tiene argumentos, especifica NULL
Verificar códigos de error!
EAGAINEAGAIN – recursos insuficientes para crear el hilo – recursos insuficientes para crear el hiloEINVALEINVAL – atributo inválido – atributo inválido
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Copyright © 2006, Intel Corporation. All rights reserved.
Programming with POSIX* Threads
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.
Eejemplo: Creación del hilo
#include <stdio.h>#include <pthread.h>
void *hello (void * arg) { printf(“Hello Thread\n”);
}
main() { pthread_t tid;
pthread_create(&tid, NULL, hello, NULL);
}
¿Qué sucede?¿Qué sucede?
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Copyright © 2006, Intel Corporation. All rights reserved.
Programming with POSIX* Threads
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.
Esperando un Thread
int pthread_join(tid, val_ptr);
pthread_t tid• manejador de un hilo a esperar
void **val_ptr• valor de salida devuelto por un hilo
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Copyright © 2006, Intel Corporation. All rights reserved.
Programming with POSIX* Threads
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.
pthread_join Detalles
Un hilo espera a que un hilo con descriptor tid termine
• Solo espera a que un hilo se una
• El hilo debe ser unible
Un valor de salida se devuelve del hilo unido
• Tipo devuelto es (void *)
• Usar NULL si no se espera un valor de retorno
ESRCH ESRCH - hilo (pthread_t) no encontrado - hilo (pthread_t) no encontradoEINVALEINVAL - hilo (pthread_t) no unible - hilo (pthread_t) no unible
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Copyright © 2006, Intel Corporation. All rights reserved.
Programming with POSIX* Threads
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.
Estados de un hilo
Los hilos Pthread tienen dos estados
• Unible (joinable)
• Desacoplado (detached)
Por default los hilos son unibles
• Los recursos se mantienen hasta el pthread_join
• Pueden ser reseteados con atributos o una llamada API
Los hilos desacoplados no pueden unirse
• Los recursos pueden reclamarse en la terminación
• No se pueden resetear a ser unibles
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Copyright © 2006, Intel Corporation. All rights reserved.
Programming with POSIX* Threads
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.
Ejemplo: Múltiples Hilos
#include <stdio.h>#include <pthread.h>#define NUM_THREADS 4
void *hello (void *arg) { printf(“Hello Thread\n”);
} main() { pthread_t tid[NUM_THREADS]; for (int i = 0; i < NUM_THREADS; i++) pthread_create(&tid[i], NULL, hello, NULL);
for (int i = 0; i < NUM_THREADS; i++) pthread_join(tid[i], NULL);}
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Copyright © 2006, Intel Corporation. All rights reserved.
Programming with POSIX* Threads
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.
¿Qué falla?
¿Qué se muesta de myNum?
void *threadFunc(void *void *threadFunc(void *pArg) { ) { int* p = (int*)pArg;int* p = (int*)pArg; int myNum = *p; printf( “Thread number %d\n”, myNum);}}. . .. . .// from main():// from main():for (int i = 0; i < numThreads; i++) {for (int i = 0; i < numThreads; i++) { pthread_create(&tid[i], NULL, threadFunc, &i);pthread_create(&tid[i], NULL, threadFunc, &i);}}
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Copyright © 2006, Intel Corporation. All rights reserved.
Programming with POSIX* Threads
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.
for(int i=0;i<numThreads;i++) {pthread_create(&tid[i], NULL, thread, (void *) &i);
}
void *thread(void *pArg){ int *p =(int *) arg; int mynum = *p;
printf(“…….. %d\n",mynum);
pthread_exit(NULL);}
i=0x0001004
pArg=0x0001008
p=0x000100C
mynum=0x0001010
0
0x0001004
1
1
1
Contenido de la dirección 0x0001004Contenido de la dirección 0x0001004
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Copyright © 2006, Intel Corporation. All rights reserved.
Programming with POSIX* Threads
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.
Solución – Almacenamiento “Local”
void *threadFunc(void *void *threadFunc(void *pArg) ) { { int myNum = *((int*)pArg)(int*)pArg); printf( “Thread number %d\n”, myNum);}}. . .. . .
// from main():// from main():for (int i = 0; i < numThreads; i++) {for (int i = 0; i < numThreads; i++) { tNum[i] = i;tNum[i] = i; pthread_create(&tid[i], NULL, threadFunc, pthread_create(&tid[i], NULL, threadFunc, &tNum[i]&tNum[i]););}}
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Copyright © 2006, Intel Corporation. All rights reserved.
Programming with POSIX* Threads
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.
Pthreads Variables Mutex
Simple, flexible, y eficiente
Permiten estructuras de programación correctas para evitar condiciones de concurso
Nuevos tipos
• pthread_mutex_t• Variable mutex
• pthread_mutexattr_t• Atributos de mutex
Antes de usar, mutex debe ser inicializada
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Copyright © 2006, Intel Corporation. All rights reserved.
Programming with POSIX* Threads
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.
pthread_mutex_init
int pthread_mutex_init( mutex, attr );
pthread_mutex_t *mutex• mutex a ser inicializada
const pthread_mutexattr_t *attr• atributos a ser establecidos a mutex
ENOMEMENOMEM – memoria insuficiente para mutex – memoria insuficiente para mutexEAGAINEAGAIN – recursos insuficientes (otros que no son – recursos insuficientes (otros que no son memoria)memoria)EPERM EPERM - no privilegios para ejecutar la operación - no privilegios para ejecutar la operación
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Copyright © 2006, Intel Corporation. All rights reserved.
Programming with POSIX* Threads
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.
Inicialización Alternativa
Puede usarse el inicializador estático
PTHREAD_MUTEX_INITIALIZER
• Usa los atributos por default
El programador debe poner atención al alcance de los mutex
• Deben ser visibles a los hilos
pthread_mutex_t mtx1 = PTHREAD_MUTEX_INITIALIZER;
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Copyright © 2006, Intel Corporation. All rights reserved.
Programming with POSIX* Threads
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.
pthread_mutex_lock
int pthread_mutex_lock( mutex );
pthread_mutex_t *mutex• mutex que intenta hacer el lock
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Copyright © 2006, Intel Corporation. All rights reserved.
Programming with POSIX* Threads
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.
pthread_mutex_lock Detalles
Intenta hacer el lock del mutex
• Si el mutex está bloqueado por otro hilo, el hilo que llama al lock se bloquea
Mutex es detenido por el hilo que lo llama hasta que se desbloquea
• Mutex lock/unlock deben ser pares, si no puede ocurrir un interbloqueo
EINVAL EINVAL - mutex invalido - mutex invalidoEDEADLKEDEADLK – el hilo llamante ya es dueño del mutex – el hilo llamante ya es dueño del mutex
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Copyright © 2006, Intel Corporation. All rights reserved.
Programming with POSIX* Threads
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.
pthread_mutex_unlock
int pthread_mutex_unlock( mutex );
pthread_mutex_t *mutex• mutex a ser desbloqueado
EINVALEINVAL - mutex es inválido - mutex es inválidoEPERM EPERM - el hilo llamante no es dueño del mutex - el hilo llamante no es dueño del mutex
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Copyright © 2006, Intel Corporation. All rights reserved.
Programming with POSIX* Threads
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.
Exjemplo: Uso del mutex
#define NUMTHREADS 4pthread_mutex_t gMutex; // ¿porque debe ser global?int g_sum = 0;
void *threadFunc(void *arg) { int mySum = bigComputation(); pthread_mutex_lock( &gMutex ); g_sum += mySum; // los hilos acceden uno a la vez pthread_mutex_unlock( &gMutex );}
main() { pthread_t hThread[NUMTHREADS];
pthread_mutex_init( &gMutex, NULL ); for (int i = 0; i < NUMTHREADS; i++) pthread_create(&hThread[i],NULL,threadFunc,NULL);
for (int i = 0; i < NUMTHREADS; i++) pthread_join(hThread[i]); printf (“Global sum = %f\n”, g_sum);}
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Copyright © 2006, Intel Corporation. All rights reserved.
Programming with POSIX* Threads
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.
Variables Condición
Los semáforos son condicionales en el contador del semáforo
Las variables condición están asociadas con una condición arbitraria
• Las mismas operaciones: wait y signal
Proveen exclusión mutua
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Copyright © 2006, Intel Corporation. All rights reserved.
Programming with POSIX* Threads
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.
Variable condición y Mutex
Un mutex está asociado con una variable condición
• Protege la evaluación de la expresión condicional
• Previene condiciones de concurso entre los hilos que están enviando la señal y los hilos que esperan en la variable condición
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Copyright © 2006, Intel Corporation. All rights reserved.
Programming with POSIX* Threads
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.
Señales perdidas y falsas
Una señal a una variable de condición no se guarda
• Si no hay un hilo esperando, la señal se pierde
• Un hilo puede interbloquearse esperando una señal que no será enviada
Una variable de condición (rara vez) puede recibir señales falsas
• Si las señales se hacen predecibles la ejecución es más lenta
• Se requiere volver a probar la expresión de condición
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Copyright © 2006, Intel Corporation. All rights reserved.
Programming with POSIX* Threads
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.
Algoritmo de variables de condición
Evita problemas con señales perdidas y señales falsas
adquiere mutex;adquiere mutex;
while (condición es verdadera)while (condición es verdadera)
espera en la variable de condición;espera en la variable de condición;
ejecuta región crítica;ejecuta región crítica;
actualiza condición;actualiza condición;
envía señal a los hilos que esperan;envía señal a los hilos que esperan;
libera mutex;libera mutex;
Se niega la condición se necesita proceder
El mutex se libera automáticamente
cuando el hilo espera
Puede ser
opcional
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Copyright © 2006, Intel Corporation. All rights reserved.
Programming with POSIX* Threads
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.
Variables Condición
pthread_cond_init, pthread_cond_destroy
• Inicializa/destruye variables de condición
pthread_cond_wait
• El hilo duerme hasta que se efectúa un signal a la variable de condición
pthread_cond_signal
• Señal que libera la variable de condición
pthread_cond_broadcast
• Broadcast que libera la variable de condición
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Copyright © 2006, Intel Corporation. All rights reserved.
Programming with POSIX* Threads
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.
Tipos de variables de condición
Tipos de datos usados
• pthread_cond_t• La variable de condición
• pthread_condattr_t• Atributos de la variable de condición
Antes de usar, la variable condición (y el mutex) deben inicializarse
27
Copyright © 2006, Intel Corporation. All rights reserved.
Programming with POSIX* Threads
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.
pthread_cond_init
int pthread_cond_init( cond, attr );
pthread_cond_t *cond• variable condición a ser inicializada
const pthread_condattr_t *attr• attributos a ser establecidos en la variable de
conidiciónENOMEMENOMEM - insuficiente memoria para la variable - insuficiente memoria para la variable condicióncondiciónEAGAINEAGAIN - insuficientes recursos (diferentes a la - insuficientes recursos (diferentes a la memoria)memoria)EBUSY EBUSY - variable de condición ya inicializada - variable de condición ya inicializadaEINVALEINVAL - - attrattr inválido inválido
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Copyright © 2006, Intel Corporation. All rights reserved.
Programming with POSIX* Threads
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.
Inicialización alternativa
Puede usuarse un inicializador estático
PTHREAD_COND_INITIALIZER
• Usa los atributos por default
Los programadores deben estar atentos a la condición y alcance (del mutex)
• Debe ser visible a los hilos
pthread_cond_t cond1 = PTHREAD_COND_INITIALIZER;
29
Copyright © 2006, Intel Corporation. All rights reserved.
Programming with POSIX* Threads
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.
pthread_cond_wait
int pthread_cond_wait( cond, mutex );
pthread_cond_t *cond• Variable condición a esperar
pthread_mutex_t *mutex• Debe desbloquearse
30
Copyright © 2006, Intel Corporation. All rights reserved.
Programming with POSIX* Threads
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.
pthread_cond_wait Detalles
El hilo se bloquea esperando una señal en cond
El mutex se desbloquea
• Permite que otros hilos adquiran el lock
• Cuando llega una señal, el mutex será readquirido antes de salir del pthread_cond_wait
EINVAL EINVAL - cond o mutex inválido - cond o mutex inválidoEINVAL EINVAL - mutex diferentes para esperaas concurrentes - mutex diferentes para esperaas concurrentesEINVAL EINVAL - el hilo llamante no es dueño del mutex - el hilo llamante no es dueño del mutex
31
Copyright © 2006, Intel Corporation. All rights reserved.
Programming with POSIX* Threads
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.
pthread_cond_signal
int pthread_cond_signal( cond );
pthread_cond_t *cond• Variable condición a la que se le enviará la señal
32
Copyright © 2006, Intel Corporation. All rights reserved.
Programming with POSIX* Threads
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.
pthread_cond_signal Detalles
Envía una señal a una variable condición, desbloquea un hilo bloqueado
Si no hay hilos esperando, no se toma ninguna acción
• La señal no se guarda para futuros hilos
El hilo que envía la señal no requiere tener el mutex
• Puede ser más eficiente
• Puede haber problemas si se usan prioridades de hilos
EINVAL EINVAL - cond es inválida - cond es inválida
33
Copyright © 2006, Intel Corporation. All rights reserved.
Programming with POSIX* Threads
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.
pthread_cond_broadcast
int pthread_cond_broadcast( cond );
pthread_cond_t *cond• variable condición a recibir la señal
34
Copyright © 2006, Intel Corporation. All rights reserved.
Programming with POSIX* Threads
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.
pthread_cond_broadcast detalles
Desbloquea todos los hilos que están esperando una variable de condición
Si no hay hilos esperando, no se toma ninguna acción
• Broadcast no se almacena para hilos futuros
El hilo que envía la señal no necesita tener el mutex
EINVAL EINVAL - cond is inválida - cond is inválida
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Copyright © 2006, Intel Corporation. All rights reserved.
Programming with POSIX* Threads
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.
Programando con hilos POSIX* Temas cubiertos
Como crear hilos que hagan trabajo encapsulado dentro de las funciones
Coordinar acceso compartido entre hilos para evitar condiciones de concurso
36
Copyright © 2006, Intel Corporation. All rights reserved.
Programming with POSIX* Threads
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.