Michael,
I beleive -20 is the highest priority process while 19
is the lowest priority process i.e, priority rule is
"smaller the number higher the priority"
i.e, in my case
-20 ==> -20 + 20 = 0
-19 ==> -19 + 20 = 1
.....
..
18 ==> 18 + 20 = 38
19 ==> 19 + 20 = 39
We "prevent" the priority rule in this mapping. In the
current code...
-20 ===> 20 - (-20) = 40
-19 ===> 20 - (-19) = 39
-18 ===> 20 - (-18) = 38
....
19 ===> 20 - 19 = 1
This mapping violates the "priority rule". While I
correct my earlier statement from
niceval = 20 + p->nice to
niceval = 21 + p->niceval (Just to make sure it indeed
ranges from 1-40 )I still beleive it should be "+"
instead of "-".
--Asok
--- Michael Covi <thebaron22@optushome.com.au> wrote:
> This seems to be correct to me. Remember 20 - ( -20)
> = 40
>
> and it says that it returns 40..1 instead of -20..19
>
> 40...20...1
> -20...0..19
>
> etc
>
> On Sun, 9 Dec 2001, Asok Tiyyagura wrote:
>
> > Hi guys,
> >
> > I am a newbie. Please correct me if I am wrong.
> The
> > function sys_getpriority() returns max priority of
> a
> > group of processes. But the code below seems to
> have a
> > bug. I believe the statement
> >
> > niceval = 20 - p->nice;
> >
> > should have been
> >
> > niceval = 20 + p->nice;
> >
> > Thanks in advance,
> > Asok
> >
> > /*
> > * Ugh. To avoid negative return values,
> "getpriority
> > ()" will
> > * not return the normal nice-value, but a negated
> > value that
> > * has been offset by 20 (ie it returns 40..1
> instead
> > of -20..19)
> > * to stay compatible.
> > */
> > asmlinkage long sys_getpriority(int which, int
> who)
> > {
> > struct task_struct *p;
> > long retval = -ESRCH;
> >
> > if (which > 2 || which < 0)
> > return -EINVAL;
> >
> > read_lock(&tasklist_lock);
> > for_each_task (p) {
> > long niceval;
> > if (!proc_sel(p, which, who))
> > continue;
> > niceval = 20 - p->nice;
> > if (niceval > retval)
> > retval = niceval;
> > }
> > read_unlock(&tasklist_lock);
> >
> > return retval;
> > }
> >
> >
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