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x86: fix freeze in x86_64 RTC update code in time_64.c 

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 <dpreed@reed.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
David P. Reed 2007-11-14 17:47:35 -05:00 committed by Thomas Gleixner
parent fa6a1a554b
commit c399da0d97
1 changed files with 4 additions and 7 deletions
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11
arch/x86/kernel/time_64.c
View File

@ -82,18 +82,15 @@ static int set_rtc_mmss(unsigned long nowtime)
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 nowtime)
CMOS_WRITE(control, RTC_CONTROL);
CMOS_WRITE(freq_select, RTC_FREQ_SELECT);
spin_unlock(&rtc_lock);
spin_unlock_irqrestore(&rtc_lock, flags);
return retval;
}