Fix hard freeze on x86_64 when the ntpd service calls
update_persistent_clock()
A repeatable but randomly timed freeze has been happening in Fedora 6
and 7 for the last year, whenever I run the ntpd service on my AMD64x2
HP Pavilion dv9000z laptop. This freeze is due to the use of
spin_lock(&rtc_lock) under the assumption (per a bad comment) that
set_rtc_mmss is called only with interrupts disabled. The call from
ntp.c to update_persistent_clock is made with interrupts enabled.
Signed-off-by: David P. Reed <[EMAIL PROTECTED]>
---
I have thoroughly tested this patch on a number of x86_64 machines
with various numbers of cores and chipsets, using 2.6.24rc2 kernel
source.
Index: linux-2.6/arch/x86/kernel/time_64.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/time_64.c
+++ linux-2.6/arch/x86/kernel/time_64.c
@@ -82,18 +82,15 @@ static int set_rtc_mmss(unsigned long no
int retval = 0;
int real_seconds, real_minutes, cmos_minutes;
unsigned char control, freq_select;
+ unsigned long flags;
/*
- * IRQs are disabled when we're called from the timer interrupt,
- * no need for spin_lock_irqsave()
+ * set_rtc_mmss is called when irqs are enabled, so disable irqs here
*/
-
- spin_lock(&rtc_lock);
-
+ spin_lock_irqsave(&rtc_lock, flags);
/*
* Tell the clock it's being set and stop it.
*/
-
control = CMOS_READ(RTC_CONTROL);
CMOS_WRITE(control | RTC_SET, RTC_CONTROL);
@@ -138,7 +135,7 @@ static int set_rtc_mmss(unsigned long no
CMOS_WRITE(control, RTC_CONTROL);
CMOS_WRITE(freq_select, RTC_FREQ_SELECT);
- spin_unlock(&rtc_lock);
+ spin_unlock_irqrestore(&rtc_lock, flags);
return retval;
}
-
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