Messages in this thread | | | Date | Mon, 14 Feb 2011 16:52:44 +0200 | From | "Kirill A. Shutemov" <> | Subject | Re: [PATCH, v6 2/3] Implement timer slack notifier chain |
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On Mon, Feb 14, 2011 at 02:32:23PM +0100, Thomas Gleixner wrote: > On Mon, 14 Feb 2011, Kirill A. Shutsemov wrote: > > > From: Kirill A. Shutemov <kirill@shutemov.name> > > > > Process can change its timer slack using prctl(). Timer slack notifier > > call chain allows to react on such change or forbid it. > > So we add a notifier call chain and more exports to allow what ?
To allow the cgroup contoller validate the value.
> > --- a/kernel/sys.c > > +++ b/kernel/sys.c > > @@ -1691,15 +1691,10 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3, > > error = perf_event_task_enable(); > > break; > > case PR_GET_TIMERSLACK: > > - error = current->timer_slack_ns; > > + error = prctl_get_timer_slack(); > > What's the point of replacing current->timer_slack_ns with a > function which does exactly the same ?
To keep it consistent. BTW, prctl_get_seccomp() does the same.
> > > +long prctl_set_timer_slack(long timer_slack_ns) > > +{ > > + int err; > > + > > + /* Reset timer slack to default value */ > > + if (timer_slack_ns <= 0) { > > + current->timer_slack_ns = current->default_timer_slack_ns; > > + return 0; > > That does not make any sense at all. Why is setting > default_timer_slack_ns not subject to validation ?
Hm.. In case of cgroup_timer_slack it's always valid. But, yes, in general, we should validate it.
> Why is it treaded seperately ?
What do you mean?
> > + } > > + > > + err = blocking_notifier_call_chain(&timer_slack_notify_list, > > + timer_slack_ns, NULL); > > + if (err == NOTIFY_DONE) > > + current->timer_slack_ns = timer_slack_ns; > > + > > + return notifier_to_errno(err); > > Thanks, > > tglx
-- Kirill A. Shutemov
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