I tried to write a kernel module (4.8.1), and if I use
if (hrtimer_cancel(&hr_timer) == 1) {
u64 remaining = ktime_to_ns(hrtimer_get_remaining(&hr_timer));
printk("(%llu ns; %llu us)\n", remaining,
(unsigned long long) (remaining/1e3));
}
he causes this error
error: SSE register return with SSE disabled
printk("\t\t(%llu ns; %llu us)\n",
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
remaining,
~~~~~~~~~~
(unsigned long long) (remaining/1e3));
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
and if i use
if (hrtimer_cancel(&hr_timer) == 1) {
u64 remaining = ktime_to_ns(hrtimer_get_remaining(&hr_timer));
printk("(%llu ns; %llu us)\n", remaining,
(unsigned long long) (remaining/1000));
}
It works without problems.
So why can't you use scientific notation in the kernel? I mean, I think it's much easier and more readable to use 1e3; 1e6; 1e9instead 1000; 1000000; 1000000000.
Is it just portability / reliability?
Or something like (in this case)
Do you need ns? Use ktime_to_ns
We need you? Use ktime_to_us
Do you need ms? Usektime_to_ms
PS I tried with a simple .c program and it works without problems.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
void error_handler(const char *msg)
{
perror(msg);
exit(EXIT_FAILURE);
}
unsigned long parse_num(const char *number)
{
unsigned long v;
char *p;
errno = 0;
v = strtoul(number, &p, 10);
if (errno != 0 || *p != '\0')
error_handler("parse_num | strtoul");
return v;
}
int main(int argc, char *argv[])
{
if (argc != 2)
{
fprintf(stderr, "Usage: %s number_greater_than_1000\n", argv[0]);
return EXIT_FAILURE;
}
unsigned long number = parse_num(argv[1]);
if (number < 1e3 || number > 1e6)
{
fprintf(stderr, "Need to be a number in range (%lu, %lu)\n", (unsigned long) 1e3, (unsigned long) 1e6);
return EXIT_FAILURE;
}
printf("Original: %lu\tScaled: %lu\n", number, (unsigned long) (number/1e3));
return EXIT_SUCCESS;
}