From: Jiri Slaby <jirislaby@gmail.com>
To: Ralf Baechle <ralf@linux-mips.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-mips@linux-mips.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/1] Char: ds1286, eliminate busy waiting
Date: Tue, 29 Jul 2008 11:42:08 +0200 [thread overview]
Message-ID: <488EE5F0.7020302@gmail.com> (raw)
In-Reply-To: <20080728230533.GB1430@linux-mips.org>
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();
prev parent reply other threads:[~2008-07-29 9:42 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-07-25 17:49 [PATCH 1/1] Char: ds1286, eliminate busy waiting Jiri Slaby
2008-07-28 23:05 ` Ralf Baechle
2008-07-29 9:42 ` Jiri Slaby [this message]
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