while loop in a multi-core cpu

* while loop in a multi-core cpu
       [not found] ` <CAKcohPxHzbQvztgQMQaFq-EoXGbpfQxi1HpPV9nogBUaQ+PUSw@mail.gmail.com>
@ 2023-01-15 16:07   ` Yunjie Gu
  2023-01-16  3:05     ` Chen, Hongzhan
  0 siblings, 1 reply; 10+ messages in thread
From: Yunjie Gu @ 2023-01-15 16:07 UTC (permalink / raw)
  To: xenomai

Hi Guys,

We are trying to develop a polling mode thread to skip the delay of
the interrupt response. This is done by a while loop to check the
hardware (say a gpio or a timer) continuously. When we did this we
found that the system was frozen, meaning that the other cores are not
functioning when we run a polling loop on a single core. But if we do
the same in a normal Linux thread, the system is not frozen. I'm just
wondering if polling mode is allowed for xenomai, or if we did
anything incorrectly. A simple test piece of code to replicate this is
attached below. Our code runs on RaspberryPiCM4 (four-core ARM V7l)
with Linux 4.19 and xenomai 3.1.

Best Regards,
Yunjie

#include <stdio.h>
#include <unistd.h>
#include <alchemy/task.h>
#include <alchemy/timer.h>
#include <alchemy/sem.h>
#include <rtdm/uapi/rtdm.h>
#include <fcntl.h>
#include <linux/types.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
RT_TASK demo_task;

void demo(void *arg)
{
    RT_TASK *curtask;
    RT_TASK_INFO curtaskinfo;

    curtask=rt_task_self();
    rt_task_inquire(curtask,&curtaskinfo);

    printf("Task name : %s \n", curtaskinfo.name);

        //------------------ hello world --------------------
    while (1)
    {
        printf("Hello World!\n");
    }

}

int main(int argc, char* argv[])
{
    char  str[10];

    // rt_print_auto_init(1);

    mlockall(MCL_CURRENT|MCL_FUTURE);

    printf("start task\n");

    sprintf(str,"hello");
    rt_task_create(&demo_task, str, 0, 50, 0);

    rt_task_start(&demo_task, &demo, 0);
    pause();
    rt_task_delete(&demo_task);
}

^ permalink raw reply	[flat|nested] 10+ messages in thread