テストするためのテストプログラムを作成しましたSCHED_FIFO。スレッドSCHED_FIFOによってプリエンプションできないことを学びました。SCHED_OTHERしかし、同じプログラムを複数回実行した場合の結果を説明することはできませんでした。
/* Includes */
#include <unistd.h> /* Symbolic Constants */
#include <sys/types.h> /* Primitive System Data Types */
#include <errno.h> /* Errors */
#include <stdio.h> /* Input/Output */
#include <stdlib.h> /* General Utilities */
#include <pthread.h> /* POSIX Threads */
#include <string.h> /* String handling */
#include <sched.h>
/* prototype for thread routine */
void print_message_function ( void *ptr );
void print_message_function1 ( void *ptr );
/* struct to hold data to be passed to a thread
* this shows how multiple data items can be passed to a thread
*/
typedef struct str_thdata
{
int thread_no;
int thread_value;
char message[100];
} thdata;
int main()
{
pthread_t thread1, thread2; /* thread variables */
thdata data1, data2; /* structs to be passed to threads */
/* initialize data to pass to thread 1 */
data1.thread_no = 1;
data1.thread_value = 0;
strcpy(data1.message, "Hello!");
/* initialize data to pass to thread 2 */
data2.thread_no = 2;
data2.thread_value = 10000;
strcpy(data2.message, "Hi!");
/* create threads 1 and 2 */
pthread_create (&thread1, NULL, (void *) &print_message_function, (void *) &data1);
pthread_create (&thread2, NULL, (void *) &print_message_function1, (void *) &data2);
/* Main block now waits for both threads to terminate, before it exits
* If main block exits, both threads exit, even if the threads
* have not finished their work
*/
pthread_join(thread1, NULL);
pthread_join(thread2, NULL);
/* exit */
exit(0);
} /* main() */
/**
* print_message_function is used as the start routine for the threads used
* it accepts a void pointer
**/
void print_message_function ( void *ptr )
{
thdata *data;
data = (thdata *) ptr; /* type cast to a pointer to thdata */
struct sched_param param;
//int priority=10;
/* sched_priority will be the priority of the thread */
//param.sched_priority = priority;
/* only supported policy, others will result in ENOTSUP */
int policy = SCHED_OTHER;
/* scheduling parameters of target thread */
pthread_setschedparam(pthread_self(), policy, ¶m);
printf("Thread %d says sched policy %d \n", data->thread_no, SCHED_OTHER);
pthread_getschedparam(pthread_self(),&policy,¶m);
printf("Thread %d says %s %d \n", data->thread_no, data->message,policy);
int i=0;
/* do the work */
printf("Thread %d says %s %d \n", data->thread_no, data->message,(int)pthread_self());
for(i=0;i<100;i++)
printf("Thread %d says %d \n", data->thread_no,data->thread_value++);
pthread_exit(0); /* exit */
} /* print_message_function ( void *ptr ) */
void print_message_function1 ( void *ptr )
{
thdata *data;
data = (thdata *) ptr; /* type cast to a pointer to thdata */
struct sched_param param;
int priority=10;
/* sched_priority will be the priority of the thread */
param.sched_priority = priority;
/* only supported policy, others will result in ENOTSUP */
int policy = SCHED_FIFO;
/* scheduling parameters of target thread */
pthread_setschedparam(pthread_self(), policy, ¶m);
printf("Thread %d says sched policy %d \n", data->thread_no, SCHED_FIFO);
pthread_getschedparam(pthread_self(),&policy,¶m);
printf("Thread %d says %s %d \n", data->thread_no, data->message,policy);
int i=0;
/* do the work */
printf("Thread %d says %s %d \n", data->thread_no, data->message,(int)pthread_self());
for(i=0;i<100;i++)
printf("Thread %d says %d \n", data->thread_no,data->thread_value++);
pthread_exit(0); /* exit */
} /* print_message_function ( void *ptr ) */
複数の実行で予期しない結果が発生しました。スレッドSCHED_FIFOがプリエンプションされていSCHED_OTHERます。つまり、プログラムに従って、スレッド2はFIFOモードで、スレッド1はSCHED_OTHERモードです。thread2がthread1にプリエンプションされるのを何度も見ました。
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