Re: spin_lock error in arch/i386/kernel/time.c on APM resume

[George Anzinger <george@mvista.com>]

Zwane Mwaikambo wrote:
> On Sat, 12 Mar 2005, George Anzinger wrote:
> 
> 
>>I agree.  Still in all that follows, no one has addressed the apparent race
>>described above.  The reason the system reported the errors that started this
>>thread is that the APM restore code was trying to read the cmos clock (I
>>assume to set the xtime clock) WHILE the timer interrupt code what trying to
>>set the cmos clock from xtime.
> 
> 
> Doesn't my reply explain the actual problem? The code path being;

Sorry, I just didn't look at the apm code.  My bad.

-g
> 
> arch/i386/kernel/apm.c
> suspend()
> 	write_seqlock_irq(xtime_lock)
> 	...
> 	write_sequnlock_irq(xtime_lock)
> 	<interrupts enabled>
> 	device_power_up()
> 		timer_resume()
> 			get_cmos_time();

S
> So this covers the problem that the reporter reported, so yes it's setting 
> xtime but we shouldn't be taking interrupts in the first place, so i 
> posted the patch to cover that. APM was clearly violating PM resume 
> procedures.
> 
> Thanks,
> 	Zwane

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