/* critical.c
*
* compile with gcc critical.c -o critical -lrt -lpthread
*
* 当主线程和A,B优先级相同时,结果为aaaaabbbbb
* 当主线程的优先级比另外两个高时, 结果为bbbbbaaaaa
*/
#include /* header file for pthreads */
#include /* header file for POSIX conformance */
#include /* header file for POSIX time management */
#include /* header file for POSIX scheduling */
#include /* header file for standard input/outputlibrary */
#define _REENTRANT /* macro to ensure system calls are reentrant */
void *threadA(void *); /* predefine threadA routine */
void *threadB(void *); /* predefine threadB routine */
pthread_t threadA_id,threadB_id,main_id; /* thread identifiers */
pthread_attr_t attrA,attrB; /* 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 */
unsigned long mask = 1; /* 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);
/* Change priority and policy of main thread */
main_id = pthread_self();
param.sched_priority=priority_min;
status = pthread_setschedparam(main_id, policy, ¶m);
if (status != 0) perror("pthread_setschedparam"); /* error check */
/* Create threadA */
param.sched_priority = priority_min;
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; /* so that B runs with a higher priority than A */
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");
/* 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 */
printf("\nmain() reporting that all threads have terminated\n");
return(0);
} /* end of main */
void *threadA(void *arg)
{
int j;
for(j=1;j<=5;j++){
printf("a");
}
return (NULL);
}
void *threadB(void *arg)
{
int j;
for(j=1;j<=5;j++){
printf("b");
}
return (NULL);
}
