kernel module compilation error of macro for_each_process - c

Question

I am trying to compile a kernel module program to list tasks linearly, such that if you run the command ps -el should have the same or similar output. my textbook says:
"In the Linux kernel, the for_each_process() macro easily allows iteration over all current tasks in the system:
#include <linux/sched.h>
struct task_struct *task;
for_each_process(task) {
/* on each iteration task points to the next task */
}
so I have the following:
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/sched.h>
int tasks_lister_linear_init(void)
{
printk(KERN_INFO "Loading module...\n");
struct task_struct *task;
for_each_process(task)
{
printk(KERN_INFO "pid: %d | pname: %s | state: %ld\n", task->pid, task-
>comm, task->state);
}
printk(KERN_INFO "Module loaded.\n");
return 0;
}
void tasks_lister_linear_exit(void)
{
printk(KERN_INFO "Module removed.\n");
}
module_init(tasks_lister_linear_init);
module_exit(tasks_lister_linear_exit);
and when I go to make, I get an error saying
implicit declaration of function ‘for_each_process’; did you mean ‘for_each_node’?
expected ‘;’ before ‘{’ token
| for_each_process(task) {
| ^~
| ;
yet every call to this I have seen has not had a semicolon following. any advice on these errors would be greatly appreciated

Answer 1

You are probably using a newer kernel version. In later kernels, the macro for_each_process has been moved to the
#include <linux/sched/signal.h>
instead of
#include <linux/sched.h>