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Commit c399da0d authored by David P. Reed's avatar David P. Reed Committed by Thomas Gleixner
Browse files

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: default avatarDavid P. Reed <dpreed@reed.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent fa6a1a55

arch/x86/kernel/time_64.c

+4 −7
Original line number Diff line number Diff line
@@ -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;

}