Re: The HPET issue on Linux

[Gleb Natapov <gleb@redhat.com>]

On Wed, Jan 06, 2010 at 05:48:52PM +0800, Sheng Yang wrote:
> Hi Beth
> 
> I still found the emulated HPET would result in some boot failure. For 
> example, on my 2.6.30, with HPET enabled, the kernel would fail check_timer(), 
> especially in timer_irq_works().
> 
> The testing of timer_irq_works() is let 10 ticks pass(using mdelay()), and 
> want to confirm the clock source with at least 5 ticks advanced in jiffies. 
> I've checked that, on my machine, it would mostly get only 4 ticks when HPET 
> enabled, then fail the test. On the other hand, if I using PIT, it would get 
> more than 10 ticks(maybe understandable if some complementary ticks there). Of 
> course, extend the ticks count/mdelay() time can work.
> 
> I think it's a major issue of HPET. And it maybe just due to a too long 
> userspace path for interrupt injection... If it's true, I think it's not easy 
> to deal with it.
> 
PIT tick are reinjected automatically, HPET should probably do the same
although it may just create another set of problems.

--
			Gleb.