* [PATCH 1/1] Char: ds1286, eliminate busy waiting
@ 2008-07-25 17:49 Jiri Slaby
2008-07-28 23:05 ` Ralf Baechle
0 siblings, 1 reply; 3+ messages in thread
From: Jiri Slaby @ 2008-07-25 17:49 UTC (permalink / raw)
To: Andrew Morton; +Cc: linux-mips, linux-kernel, Jiri Slaby, Ralf Baechle
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.
Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
---
drivers/char/ds1286.c | 4 +---
1 files changed, 1 insertions(+), 3 deletions(-)
diff --git a/drivers/char/ds1286.c b/drivers/char/ds1286.c
index fb58493..5329d48 100644
--- a/drivers/char/ds1286.c
+++ b/drivers/char/ds1286.c
@@ -443,7 +443,6 @@ static void ds1286_get_time(struct rtc_time *rtc_tm)
{
unsigned char save_control;
unsigned long flags;
- unsigned long uip_watchdog = jiffies;
/*
* read RTC once any update in progress is done. The update
@@ -456,8 +455,7 @@ static void ds1286_get_time(struct rtc_time *rtc_tm)
*/
if (ds1286_is_updating() != 0)
- while (time_before(jiffies, uip_watchdog + 2*HZ/100))
- barrier();
+ msleep(20);
/*
* Only the values that we read from the RTC are set. We leave
--
1.5.6.2
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH 1/1] Char: ds1286, eliminate busy waiting
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
0 siblings, 1 reply; 3+ messages in thread
From: Ralf Baechle @ 2008-07-28 23:05 UTC (permalink / raw)
To: Jiri Slaby; +Cc: Andrew Morton, linux-mips, linux-kernel
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.
>
> Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
> Cc: Ralf Baechle <ralf@linux-mips.org>
Looks ok to me I guess. Though I don't really think it matters ...
Acked-by: Ralf Baechle <ralf@linux-mips.org>
The same condition also appears in drivers/char/rtc.c and maybe a few
others. Rtc.c has been copies and modified several times.
Ralf
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH 1/1] Char: ds1286, eliminate busy waiting
2008-07-28 23:05 ` Ralf Baechle
@ 2008-07-29 9:42 ` Jiri Slaby
0 siblings, 0 replies; 3+ messages in thread
From: Jiri Slaby @ 2008-07-29 9:42 UTC (permalink / raw)
To: Ralf Baechle; +Cc: Andrew Morton, linux-mips, linux-kernel
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();
^ permalink raw reply [flat|nested] 3+ messages in thread
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2008-07-28 23:05 ` Ralf Baechle
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