CSE 451: Introduction to Operating Systems

Section 5, April/26/2001

Jochen Jäger

1. Project 2 turn in

2. Project 3 hand out

3. pthread

4. threads on other systems

Threadpool_test.c

#include <stdio.h>

#include <stdlib.h>

#include <unistd.h>

#include <pthread.h>

#include <errno.h>

#include "threadpool.h"

extern int errno;

void dispatch_to_me(void *arg) {

int seconds = (int) arg;

fprintf(stdout, " in dispatch %d\n", seconds);

sleep(seconds);

fprintf(stdout, " done dispatch %d\n", seconds);

}

int main(int argc, char **argv) {

threadpool tp;

tp = create_threadpool(2);

fprintf(stdout, "**main** dispatch 3\n");

dispatch(tp, dispatch_to_me, (void *) 3);

fprintf(stdout, "**main** dispatch 6\n");

dispatch(tp, dispatch_to_me, (void *) 6);

fprintf(stdout, "**main** dispatch 7\n");

dispatch(tp, dispatch_to_me, (void *) 7);

fprintf(stdout, "**main** done first\n");

sleep(20);

fprintf(stdout, "\n\n");

fprintf(stdout, "**main** dispatch 3\n");

dispatch(tp, dispatch_to_me, (void *) 3);

fprintf(stdout, "**main** dispatch 6\n");

dispatch(tp, dispatch_to_me, (void *) 6);

fprintf(stdout, "**main** dispatch 7\n");

dispatch(tp, dispatch_to_me, (void *) 7);

fprintf(stdout, "**main done second\n");

sleep(20);

exit(-1);

}
int pthread_create(pthread_t * thread, pthread_attr_t * attr, void * (*start_routine)(void *), void * arg);

pthread_create creates a new thread of control that executes concurrently with the calling thread.

Example for locking:

pthread_mutex_t Locker = PTHREAD_MUTEX_INITIALIZER;

...

pthread_mutex_lock(&Locker);

... do critical stuff

pthread_mutex_unlock(&Locker);

#include <pthread.h>

#include <stdio.h>

void *child(void *) {

printf("child\n");

int *result = new int; // storage for exit status

*result = 25; // exit-Status

return result;

}

int main() {

pthread_t pid;

void *res;

printf("Create child\n");

pthread_create(&pid,NULL,child,NULL);

printf("Pid of child: %d\n",pid);

pthread_join(pid,&res);

printf("result from child: %d\n",*(int *)res);

delete res;

}

Threads and synchronization on other systems

Create a thread:

POSIX:

pthread_create(&threadID, &threadAttr, threadRoutine, ThreadArg);

C:

cthread_t tid;

tid = cthread_fork(threadRoutine, threadArg);

Win32:

HANDLE hThread;

hThread = CreateThread(NULL, stackSize, (LPTHREAD_START_ROUTINE) threadRoutine, (LPVOID) threadArg, 0, &threadId);

OS/2:

TID tid;

tid = _beginthread(threadRoutine, NULL, stackSize, threadArg);

Thread Synchronization (e.g. Mutex locks):

POSIX:

pthread_mutex_t lock;

pthread_mutex_lock(&lock);

pthread_mutex_unlock(&lock);

C:

mutex_t lock;

mutex_lock(lock);

mutex_unlock(lock);

Win32:

HANDLE lock;

WaitForSingleObject(lock, INFINITE);

ReleaseMutex(lock);

OS/2:

HMTX lock;

DosRequestMutexSem(lock, timeOut); DosReleaseMutexSem(lock);