Re: do_gettimeofday vs. rdtsc in the scheduler

[Mikael Pettersson <mikpe@csd.uu.se>]

Alan Cox writes:
 > On Thu, 2002-09-19 at 12:20, Mikael Pettersson wrote:
 > >  > The local APIC timer is specified in the Intel Manual volume 3 for example.
 > >  > It's an optional feature (CPUID), but pretty much everyone has it.
 > > 
 > > Except that like everything else related to the local APIC, you're at
 > > the mercy of the competence (or lack thereof) of the BIOS implementors.
 > > - There are plenty of laptops whose CPUs have local APICs but whose
 > >   BIOSen go berserk if you enable it. There are also plenty of laptops
 > 
 > Frequently because we don't disable it again before any APM calls I
 > suspect. When a CPU goes into sleep mode you must disable PMC and local
 > apic timer interrupts.

We do on sane boxes where the APM BIOS informs us before suspending.
E.g., on my ASUS P3B-F & P4T-E suspend works with local APIC enabled
because I hooked both the NMI watchdog and local APIC to the
PM system, so we disable before suspending and restore afterwards.

The problem is that some BIOSen don't post the suspend event to
our APM driver, so we fail to disable before suspend, and some BIOSen
(like the utter crap Dell put in the Inspiron) die on all entries to
the BIOS: pull the power cord -> #SMM event -> box crashes.

/Mikael