gpt4 book ai didi

linux - SCHED_FIFO 线程在 Linux 中被 SCHED_OTHER 线程抢占

转载 作者:IT王子 更新时间:2023-10-29 01:09:02 27 4
gpt4 key购买 nike

我已经编写了一个测试程序来测试 SCHED_FIFO。我了解到 SCHED_FIFO 不能被 SCHED_OTHER 线程抢占。但是我无法解释多次运行同一个程序时获得的结果。

/* 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, &param);
printf("Thread %d says sched policy %d \n", data->thread_no, SCHED_OTHER);
pthread_getschedparam(pthread_self(),&policy,&param);

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, &param);
printf("Thread %d says sched policy %d \n", data->thread_no, SCHED_FIFO);

pthread_getschedparam(pthread_self(),&policy,&param);

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 ) */

我在多次运行中得到了意想不到的结果,我看到 SCHED_FIFOSCHED_OTHER 线程抢占,即根据程序,线程 2 在 FIFO 模式,而线程 1 是 SCHED_OTHER 模式。我多次看到 thread2 被 thread1 抢占。

有人可以帮我找出问题吗?

最佳答案

您可能使这些 sysctl 设置生效,它们是默认值:

kernel.sched_rt_period_us = 1000000
kernel.sched_rt_runtime_us = 950000

这意味着实时线程只能占用每 1 秒周期的 95%。

另见:Can't provoke Priority Inversion in C++

关于linux - SCHED_FIFO 线程在 Linux 中被 SCHED_OTHER 线程抢占,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/10287561/

27 4 0
Copyright 2021 - 2024 cfsdn All Rights Reserved 蜀ICP备2022000587号
广告合作:1813099741@qq.com 6ren.com