Re: Detangle lwkt_switch() and the idle thread and consolidate sleep variables

["Simon 'corecode' Schubert" <corecode@xxxxxxxxxxxx>]

Joerg Sonnenberger wrote:
> According to the AMD documentation, MWAIT would exit because:
>
> Events that cause an exit from the monitor event pending state include:
> ...
> - Any far control transfer that occurs between the MONITOR and the MWAIT.
>
> The exact conditions are written in the Architecture Guide, part 3. It
> should be noted that a number of Opteron CPUs have an errata if you use
> MONITOR/MWAIT in a tight loop and certain race conditions with other
> CPUs happen and you have interrupts disabled. It should also be noted
> that MWAIT produces less bus contention as well, so it should be used
> for all spinlocks.

Using it for spinlocks is rather easy, because there is just one variable to monitor.  The intel docs also indicate that there can be a MWAIT functionality to work with interrupts disabled and as interrupt as a break condition.  I'm not exactly sure how this would work, maybe the interrupt would be serviced as soon as you enable interrupts again?

cheers
 simon