/* * multithread.c * * Demonstrate use of a multi threading and scheduling using pthreads * * compile with cc multithread.c -o multithread -lrt -lpthread * */ #define _GNU_SOURCE #define _REENTRANT /* macro to ensure system calls are reentrant */ #include <pthread.h> /* header file for pthreads */ #include <unistd.h> /* header file for POSIX conformance */ #include <time.h> /* header file for POSIX time management */ #include <sched.h> /* header file for POSIX scheduling */ #include <stdio.h> /* header file for standard input/outputlibrary */ void *threadA(void *); /* predefine threadA routine */ void *threadB(void *); /* predefine threadB routine */ void *threadC(void *); /* predefine threadC routine */ pthread_t threadA_id,threadB_id,threadC_id,main_id; /* thread identifiers */ pthread_attr_t attrA,attrB,attrC; /* thread attribute structures */ struct sched_param param; /* scheduling structure for thread attributes */ int policy=SCHED_FIFO; int priority_min,priority_max; /* for range of priority levels */ /* main routine */ int main() { struct timespec start; int status; /* check that system calls return ok */ clock_gettime(CLOCK_REALTIME, &start); /* get the time */ printf("Start time is: %d seconds %d nano_seconds\n",start.tv_sec,start.tv_nsec); /* Set processor affinity */ cpu_set_t mask; CPU_ZERO(&mask); CPU_SET(0,&mask); /* use only 1 CPU core */ unsigned int len = sizeof(mask); status = sched_setaffinity(0, len, &mask); if (status < 0) perror("sched_setaffinity"); status = sched_getaffinity(0, len, &mask); if (status < 0) perror("sched_getaffinity"); /* Find priority limits */ priority_max = sched_get_priority_max(policy); priority_min = sched_get_priority_min(policy); /* Set priority and policy of main thread */ main_id = pthread_self(); param.sched_priority=priority_min+1; status = pthread_setschedparam(main_id, policy, ¶m); if (status != 0) perror("pthread_setschedparam"); /* error check */ /* Create threadA */ param.sched_priority = priority_min+1; pthread_attr_init(&attrA); status = pthread_attr_setschedpolicy(&attrA,policy); if (status != 0) perror("pthread_attr_setschedpolicy"); /* error check */ status = pthread_attr_setschedparam(&attrA,¶m); if (status != 0) perror("pthread_attr_setschedparam"); /* error check */ status = pthread_create(&threadA_id, &attrA, threadA, NULL); if (status != 0) perror("pthread_create"); /* error check */ status = pthread_setschedparam(threadA_id,policy,¶m); if (status != 0) perror("pthread_setschedparam"); /* Create threadB */ param.sched_priority = priority_min+1; pthread_attr_init(&attrB); status = pthread_attr_setschedpolicy(&attrB,policy); if (status != 0) perror("pthread_attr_setschedpolicy"); /* error check */ status = pthread_attr_setschedparam(&attrB,¶m); if (status != 0) perror("pthread_attr_setschedparam"); /* error check */ status = pthread_create(&threadB_id, &attrB, threadB, NULL); if (status != 0) perror("pthread_create"); /* error check */ status = pthread_setschedparam(threadB_id,policy,¶m); if (status != 0) perror("pthread_setschedparam"); /* Create threadC */ param.sched_priority = priority_min+1; pthread_attr_init(&attrC); status = pthread_attr_setschedpolicy(&attrC,policy); if (status != 0) perror("pthread_attr_setschedpolicy"); /* error check */ status = pthread_attr_setschedparam(&attrC,¶m); if (status != 0) perror("pthread_attr_setschedparam"); /* error check */ status = pthread_create(&threadC_id, &attrC, threadC, NULL); if (status != 0) perror("pthread_create"); /* error check */ status = pthread_setschedparam(threadC_id,policy,¶m); if (status != 0) perror("pthread_setschedparam"); /* Join threads - force main to wait for the thread to terminate */ printf("main() waiting for threads\n"); status = pthread_join(threadA_id, NULL); if (status != 0) perror("pthread_join(threadA_id, NULL)"); /* error check */ status = pthread_join(threadB_id, NULL); if (status != 0) perror("pthread_join(threadB_id, NULL)"); /* error check */ status = pthread_join(threadC_id, NULL); if (status != 0) perror("pthread_join(threadC_id, NULL)"); /* error check */ printf("\nmain() reporting that all threads have terminated\n"); return(0); } /* end of main */ void *threadA(void *arg) { int j; for(j=1;j<=10;j++){ printf("a"); } return (NULL); } void *threadB(void *arg) { int j; for(j=1;j<=10;j++){ printf("b"); } return (NULL); } void *threadC(void *arg) { int j; for(j=1;j<=10;j++){ printf("c"); } return (NULL); }