my driver test code,I want to use mod_timer to timer for 10 milliseconds, but the result is always 20 milliseconds. what’s wrong with it? ..

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/timer.h>
#include <linux/jiffies.h>
#include <linux/unistd.h>
#include <linux/delay.h>

static struct timer_list my_timer;

void my_timer_callback(struct timer_list *timer)
{
    printk("my_timer_callback called (%ld).n", jiffies);

    mod_timer(&my_timer, jiffies + msecs_to_jiffies(10));
}

static int __init my_init(void)
{
    printk("Timer module loadedn");

    timer_setup(&my_timer, my_timer_callback, 0);

    mod_timer(&my_timer, jiffies + msecs_to_jiffies(10));

    return 0;
}

static void __exit my_exit(void)
{
    printk("Timer module unloadedn");

    del_timer(&my_timer);
}

module_init(my_init);
module_exit(my_exit);

MODULE_AUTHOR("[email protected]");
MODULE_LICENSE("GPL");
MODULE_IMPORT_NS(VFS_internal_I_am_really_a_filesystem_and_am_NOT_a_driver);

dmesg result:

[   23.891867] my_timer_callback called (-27618).
[   23.921886] my_timer_callback called (-27615).
[   23.941895] my_timer_callback called (-27613).
[   23.961872] my_timer_callback called (-27611).

kernel version: 5.10

.config：
CONFIG_HZ=100