On Wed, 10 Aug 2005, Deepak Joshi wrote:
Hi all,
I read that in order to get the current time by using
do_gettimeofday( struct timeval *tv) function we need
to disable the inturrepts because we can't access both
fields of timeval struct tv_sec and tv_usec. Why is it
so ?
Timing on linux kernel are base on Timer interrupts,that are
generated by system's timing hardware at regular intervlas,
according to the value of HZ. Every time a timer interrupt occurs,
jiffies incremented. I suppose that fields of timeval struct are
computed through jiffies, so it isn't safe to read them without
first disabling interrupts.
also i read code from Linux device drivers book that
they are reading all the values in /proc interface. is
it compulsary to do so ?
When u make a implemented action to a proc file,
a specified for the kernel function will execute,
so this function must take care of time interrupts.
This is my code ....
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/time.h>
#include <asm-i386/system.h>
int init_module(void)
{
struct timeval tv;
unsigned long flags;
save_flags( flags );
cli();
do_gettimeofday(&tv);
printk("\n\t The current time is %f",( time_t
)tv.tv_sec);
restore_flags( flags );
sti();
return 0;
}
void cleanup_module(void)
{
}
Plz guide me where i am going wrong.
Thanks in advance,
Deepak Joshi.
hope to help you,
Stavros Passas
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