Re: [PATCH] clean up FIXME in do_timer_interrupt

George Anzinger
2005-03-12T02:01:11Z

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Andrew Morton wrote:
> Lee Revell <rlrevell@joe-job.com> wrote:
>
>>On Thu, 2005-03-10 at 00:42 -0800, George Anzinger wrote:
>>
>>>This patch changes the update of the cmos clock to be timer driven
>>>rather than poll driven by the timer interrupt function. If the clock
>>>is not being synced to an outside source the timer is removed and thus
>>>system overhead is nill in that case. The update frequency is still ~11
>>>minutes and missing the update window still causes a retry in 60
>>>seconds.
>>
>>No replies yet. Are there any objections to this patch?
>
>
> Nope. I think it's neat. I queued it up.

I had a nightmare about ntp coming in at the "wrong" time resulting in a
deadlock. Attached locking changes will make me sleep better :)

--
George Anzinger george@mvista.com
High-res-timers: http://sourceforge.net/projects/high-res-timers/

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Source: MontaVista Software, Inc.
Type: Defect Fix
Disposition: Pending
Description:

I was not happy with the locking on this. Two changes:
1) Turn off irq while setting the clock.
2) Call the timer code only through the timer interface
(set a short timer to do it from the ntp call).

Signed-off-by: George Anzinger <george@mvista.com>

time.c | 6 +++---
1 files changed, 3 insertions(+), 3 deletions(-)

Index: linux-2.6.12-rc/arch/i386/kernel/time.c
===================================================================
--- linux-2.6.12-rc.orig/arch/i386/kernel/time.c
+++ linux-2.6.12-rc/arch/i386/kernel/time.c
@@ -176,12 +176,12 @@ static int set_rtc_mmss(unsigned long no
int retval;

/* gets recalled with irq locally disabled */
- spin_lock(&rtc_lock);
+ spin_lock_irq(&rtc_lock);
if (efi_enabled)
retval = efi_set_rtc_mmss(nowtime);
else
retval = mach_set_rtc_mmss(nowtime);
- spin_unlock(&rtc_lock);
+ spin_unlock_irq(&rtc_lock);

return retval;
}
@@ -338,7 +338,7 @@ static void sync_cmos_clock(unsigned lon
}
void notify_arch_cmos_timer(void)
{
- sync_cmos_clock(0);
+ mod_timer(&sync_cmos_timer, jiffies + 1);
}
static long clock_cmos_diff, sleep_start;