Re: gettimeofday question

[Russell King <rmk@arm.linux.org.uk>]

On Sat, Mar 03, 2001 at 12:49:04PM +0000, Russell King wrote:
> Hi,
> 
> I've noticed that one of my machines here suffers from the "time going
> backwards problem" and so started thinking about the x86 solution.
> 
> I've come to the conclusion that it has a hole which could cause it
> to return the wrong time in one specific case:
> 
> - in do_gettimeofday(), we disable irqs (read_lock_irqsave)
> - the ISA timer wraps, but we've got interrupts disabled, so no update
>   of xtime or jiffies occurs
> - in do_slow_gettimeoffset(), we read the timer, which has wrapped
> - since jiffies_p != jiffies, we do not apply any correction
> - our idea of time is now one jiffy slow.

I never heard any response to this.  Could some knowledgeable person please
take a look at it?

Thanks.

--
Russell King (rmk@arm.linux.org.uk)                The developer of ARM Linux
             http://www.arm.linux.org.uk/personal/aboutme.html