Hi,
I will try to test how to create kernel threads and have write a
kernel module which creates a number of kernel threads running the
same function. But the results is somewhat confusing.
#include <linux/kernel.h>
#include <linux/kthread.h>
#include <linux/delay.h>
#define MAX_KTHREAD 2
struct task_struct *ktask[MAX_KTHREAD];
static int my_kthread(void *data)
{
int nr = *(int *)data;
while (!kthread_should_stop()){
ssleep(1);
printk(KERN_ALERT "This is mythread[%d].\n", nr);
}
return 0;
}
static int kthread_init(void)
{
int i;
for (i = 0; i < MAX_KTHREAD; i++){
ktask[i] = kthread_run(my_kthread, &i, "mythread[%d]", i);
}
return 0;
}
static void kthread_exit(void)
{
int i;
for (i = 0; i < MAX_KTHREAD; i++){
if (ktask[i]){
kthread_stop(ktask[i]);
ktask[i] = NULL;
}
}
}
module_init(kthread_init);
module_exit(kthread_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Shakespeare");
MODULE_DESCRIPTION("This is a test program of kthread.");
The messages on the screen are:
This is mythread[-929820448].
This is mythread[1].
This is mythread[-929820448].
This is mythread[1].
This is mythread[-929820448].
... ... ...
I wonder why the first thread's number is not zero rather than -929820448.
Furthermore, when running again with MAX_KTHREAD == 3, the messages are:
This is mythread[1].
This is mythread[2].
This is mythread[1].
This is mythread[1].
This is mythread[2].
This is mythread[1].
This is mythread[1].
This is mythread[2].
... ... ...
There should be 3 threads running, but only two of them appear. The
first thread get lost.
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