中断在内核模式下处理,但是为了处理rt linux中的中断,他们说:
我需要在内核空间和内核模块中使用RTLinux编写代码。使用QNX,您无法编写内核模块(内核未打开),您可以在用户空间中实时使用。
我的问题: 如何在内核空间中编写代码? 究竟是什么意思? 我应该在哪里修改内核??
有人请提出一些想法。udp代码:
int CreateSocket()
{
socklen_t len;
// Socket creation for UDP
acceptSocket=socket(AF_INET,SOCK_DGRAM,0);
if(acceptSocket==-1)
{
printf("Failure: socket creation is failed, failure code\n");
return 1;
}
else
{
printf("Socket started!\n");
}
memset(&addr, 0, sizeof(addr));
addr.sin_family=AF_INET;
addr.sin_port=htons(port);
addr.sin_addr.s_addr=htonl(INADDR_ANY);
rc=bind(acceptSocket,(struct sockaddr*)&addr,sizeof(addr));
if(rc== -1)
{
printf("Oh dear, something went wrong with bind()! %s\n", strerror(errno));
return 1;
}
else
{
printf("Socket an port %d \n",port);
}
while(rc!=-1)
{
len = sizeof(client);
rc=recvfrom(acceptSocket,buf, 256, 0, (struct sockaddr*) &client, &len);
//I am calculating the time here
InterruptTime = GetTimeStamp();
measurements[17] = InterruptTime;
if(rc==0)
{
printf("Server has no connection..\n");
break;
}
if(rc==-1)
{
printf("Oh dear, something went wrong with read()! %s\n", strerror(errno));
break;
}
XcpIp_RxCallback( (uint16) rc, (uint8*) buf, (uint16) port );
}
close(acceptSocket);
return 1;
}
int main()
{
CreateSocket();
while(1)
{
TASK1(Task2ms_Raster);
TASK2(Task10ms_Raster);
TASK3(Task100ms_Raster);
}
答案 0 :(得分:3)
与QNX不同,Linux内核是开源软件。这意味着您可以以任何您想要的方式修改和更改它。您从http://kernel.org获取源代码(最好使用Git克隆到本地存储库中),进行修改,添加等等。编译思考并使用它启动计算机。
请注意,从版本2.6开始的Linux也提供实时调度,这可能就足够了。
对于光栅任务执行的时间,我建议如下:
#define _POSIX_C_SOURCE 200809L
#define _XOPEN_SOURCE 500
#include <sched.h> /* for sched_setsched */
#include <unistd.h> /* for usleep */
#include <time.h> /* for clock_gettime */
#include <string.h> /* for memset */
#define MS_to_US(x) ((x)*1000)
useconds_t delta_t_us(struct timespec const *a, struct timespec const *b)
{
time_t const delta_sec = b->tv_sec - a->tv_sec;
long const delta_nsec = b->tv_nsec - a->tv_nsec;
/* this might actually overflow for "long" time intervalls"
* should be safe for a delta_t < 2ms though */
return delta_sec * 1000000 + delta_nsec / 1000;
}
void rastertask()
{
struct sched_param sparm;
memset(&sparm, 0, sizeof(sparm));
sparm.sched_priority = 10; /* 0 = lowest, 99 = highest */
sched_setscheduler(
0 /* pid, 0 ==> this process */,
SCHED_RR /* policy */,
&sparm);
unsigned int n_loop;
for(n_loop=0;;n_loop++) {
struct timespec ts_start, ts_end;
clock_gettime(CLOCK_MONOTONIC, &ts_start);
TASK1(); /* gets called every 2ms */
if( (n_loop % 5) == 0) {
TASK2(); /* get called every 5 * 2ms = 10ms */
}
if( (n_loop % 50) == 0) {
TASK2(); /* get called every 50 * 2ms = 100ms */
}
if( (n_loop % 250) == 0 ) {
/* reset loop counter when smallest common
* multiple of timing grid has been reached */
n_loop = 0;
}
clock_gettime(CLOCK_MONOTONIC, &ts_end);
useconds_t const tasks_execution_time = delta_t_us(&ts_start, &ts_end);
if( tasks_execution_time >= MS_to_US(2) ) {
/* report an error that tasks took longer than 2ms to execute */
}
/* wait for 2ms - task_execution_time so that tasks get called in
* a close 2ms timing grid */
usleep( MS_to_US(2) - tasks_execution_time );
}
}
请注意,该过程需要CAP_SYS_NICE权限(在Linux 2.6.12之前)或足够的RLIMIT_RTPRIO资源限制才能设置其优先级。