Re: Decreasing stime running confuses top

[Chuck Ebbert <cebbert@redhat.com>]

On 10/04/2007 04:00 PM, Christian Borntraeger wrote:
> Am Donnerstag, 4. Oktober 2007 schrieb Chuck Ebbert:
>> Is CONFIG_VIRT_CPU_ACCOUNTING set?
> 
> This is s390 and powerpc only, so the answer is probably no ;-)
> 

The code in fs/proc/array.c is... interesting.

1. task_stime() converts p->se.sum_exec_runtime to a clock_t

2. it calls task_utime() which does the same thing (can it change
   between the two reads?), does some calculations that yield a 
   clock_t, turns the result into a cputime and returns that

3. task_stime() then converts that result back into a clock_t and
   uses it!


static cputime_t task_stime(struct task_struct *p)
{
        clock_t stime;

        stime = nsec_to_clock_t(p->se.sum_exec_runtime) -
                        cputime_to_clock_t(task_utime(p));

        return clock_t_to_cputime(stime);
}

static cputime_t task_utime(struct task_struct *p)
{
        clock_t utime = cputime_to_clock_t(p->utime),
                total = utime + cputime_to_clock_t(p->stime);
        u64 temp;

        temp = (u64)nsec_to_clock_t(p->se.sum_exec_runtime);

        if (total) {
                temp *= utime;
                do_div(temp, total);
        }
        utime = (clock_t)temp;

        return clock_t_to_cputime(utime);
}