Re: [PATCH] clean up FIXME in do_timer_interrupt

From: George Anzinger
Date: Fri Mar 11 2005 - 21:02:20 EST

Andrew Morton wrote:
Lee Revell <rlrevell@xxxxxxxxxxx> 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

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

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@xxxxxxxxxx>

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);
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;