Re: [PATCH 1/3] signal: sys_rt_sigtimedwait: simplify the timeout logic

[Oleg Nesterov <oleg@redhat.com>]

On 04/25, Linus Torvalds wrote:
>
> On Mon, Apr 25, 2011 at 10:26 AM, Oleg Nesterov <oleg@redhat.com> wrote:
> >
> > If only I knew what this comment could say except
> >
> >        /* Why do we add (tv_sec || tv_nsec) ?  */
> >
> > I'd better send 4/3 which simply removes this (I hope) unneeded code.
>
> It's to guarantee that timeout is at least one tick more than asked
> for, because the rule is that you really have to wait for AT LEAST the
> time asked for.

Aah, thanks. This makes sense. I'll add the comment.

> So "+ (tv_sec || tv_nsec)" is just the "+1" for the "not zero timeout" case.

So, we have

	timeout = timespec_to_jiffies(ts) + (tv_sec || tv_nsec);
	...

	if (timeout)
		timeout = schedule_timeout_interruptible(timeout);

Perhaps it makes sense to turn this code into

	timeout = timespec_to_jiffies(ts);

	if (timeout)
		// make sure we sleep at least the time we asked for
		timeout = schedule_timeout_interruptible(timeout + 1);

Assuming that timespec_to_jiffies() always returns nonzero if ts is
"not zero timeout". I think it does.

Oleg.