Re: [PATCH 1/1] Char: ds1286, eliminate busy waiting

[Jiri Slaby <jirislaby@gmail.com>]

Ralf Baechle napsal(a):
> On Fri, Jul 25, 2008 at 07:49:58PM +0200, Jiri Slaby wrote:
>
> > ds1286_get_time(); is not called from atomic context, sleep for 20 ms is
> > better choice than a (home-made) busy waiting for such a situation.
> Looks ok to me I guess.  Though I don't really think it matters ...
I think RT people has different opinion ;).

> The same condition also appears in drivers/char/rtc.c and maybe a few
> others.  Rtc.c has been copies and modified several times.
In rtc.c there is something completely different:
        while (rtc_is_updating() != 0 &&
               time_before(jiffies, uip_watchdog + 2*HZ/100))
                cpu_relax();

It's a conditional busy-waiting. It reads the rtc status after each busy 
cycle while in the ds1286 there was
        if (ds1286_is_updating() != 0)
                while (time_before(jiffies, uip_watchdog + 2*HZ/100))
                        barrier();