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From
SubjectRe: killing a kernel thread.
On Fri, 17 Oct 2003, Suresh Subramanian wrote:

> Hello everybody
>
> How do i kill a kernel thread ?
>
> Thanks.
>

From:

Vladimir Kondratiev <vladimir.kondratiev@intel.com>

#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/proc_fs.h>
#include <linux/vmalloc.h>
#include <asm/uaccess.h>

typedef struct kt_priv_struct {
int nthreads; /**< let's count how many times kernel_thread succeeded */
int pid;
wait_queue_head_t wq; /**< kthread sleep here */
struct completion exited;
__u32 volatile status;
} kt_priv_t;
static kt_priv_t the_data;

static int kt_thread(void* arg)
{
kt_priv_t* priv=(kt_priv_t*)arg;
daemonize();
reparent_to_init();
snprintf(current->comm,sizeof(current->comm),"kth_%d",priv->nthreads);
++priv->nthreads;
while (!test_bit(0,&priv->status)) {
/* framework for periodical execution */
unsigned long to=HZ; /* timeout for periodical maintenance */
do {
to=interruptible_sleep_on_timeout(&priv->wq,to);
} while ( !signal_pending(current) && to>0 );
if (signal_pending(current)) {
spin_lock_irq(&current->sigmask_lock);
flush_signals(current);
spin_unlock_irq(&current->sigmask_lock);
}
/* thread body - for this simple example do nothing */
}
complete_and_exit(&priv->exited,0);
}
static void kt_start(kt_priv_t* priv)
{
if (priv->pid>0) return;
init_completion(&priv->exited);
init_waitqueue_head(&priv->wq);
priv->status=0;
priv->pid=kernel_thread(kt_thread,priv,0);
}
static void kt_stop(kt_priv_t* priv)
{
if (priv->pid>0 && (0==test_and_set_bit(0,&priv->status))) {
kill_proc(priv->pid,SIGHUP,1);
wait_for_completion(&priv->exited);
priv->pid=0;
}
}
static int kt_proc_read(char* buf,char** start,off_t offset,int
count,int* eof,void* data)
{
kt_priv_t* priv=(kt_priv_t*)data;
int len=0;
len+=sprintf(buf+len,"nthreads = %d\n",priv->nthreads);
len+=sprintf(buf+len,"pid = %d\n",priv->pid);
*eof=1;
return len;
}
static int kt_proc_write(struct file *file, const char *buffer, unsigned
long count, void *data)
{
char *buf;
kt_priv_t* priv=(kt_priv_t*)data;
int rc = count;
if (count<1)
{
return -EINVAL;
}
buf = vmalloc(count+1);
if (!buf) return -ENOMEM;
buf[count]='\0';
if (copy_from_user(buf,buffer,count))
{
rc=-EFAULT;
goto out;
}
switch (buf[0])
{
case '+':
kt_start(priv);
break;
case '-':
kt_stop(priv);
break;
}
out:
vfree(buf);
return rc;
}
static char* kt_proc_name="kthread";

static int kt_mod_init(void)
{
struct proc_dir_entry *p;
kt_priv_t* priv=&the_data;
memset(priv,0,sizeof(*priv));
p=create_proc_read_entry(kt_proc_name,0666,NULL,kt_proc_read,priv);
if (p) {
SET_MODULE_OWNER(p);
p->write_proc=kt_proc_write;
}
return 0;
}
static void kt_mod_exit(void)
{
kt_stop(&the_data);
remove_proc_entry(kt_proc_name,NULL);
}
module_init(kt_mod_init);
module_exit(kt_mod_exit);

MODULE_AUTHOR("Vladimir Kondratiev <vladimir.kondratiev@intel.com>");
MODULE_DESCRIPTION("Kernel thread example");
MODULE_LICENSE("GPL");



Cheers,
Dick Johnson
Penguin : Linux version 2.4.22 on an i686 machine (797.90 BogoMips).
Note 96.31% of all statistics are fiction.


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