linux kernel module: kernel method undefined (kthread_create_on_cpu)

The method

struct task_struct *kthread_create_on_cpu(int(*threadfn)(void *data),
    void *data, unsigned int cpu,
    const char *namefmt)

is defined in kthread.c file and prototyped in kthread.h. But it is not exported.

In my driver I want to start a kthread on a given CPU, so I do:

#include <linux/kthread.h>

int udpsrv_start_single( unsigned int cpu)
{
     DEBUG_PRINT_INFO( "[udpsrv] udpsrv_start: Initializing...n");
     //(...)
     kthread->thread = kthread_create_on_cpu((void *)kthread_start_single, 
                                                      NULL, cpu, "mpsrv");
     //(...)

I can compile but I get linkage error on resolving module symbols on MODPOST:

1>    LD [M]  /tmp/VisualKernel/mpsrvlkm.o
1>    Building modules, stage 2.
1>    MODPOST 1 modules
1>EXEC : warning : "kthread_create_on_cpu"[/tmp/VisualKernel/mpsrvlkm.ko] undefined!

How should I proceed? How to import this symbol or what to do instead?

Answer

kthread_create_on_cpu is not exported by kernel, it is internal function used by CPU hotplug threads (see linux/smpboot.h).

I suggest you to use kthread_bind instead.