Re: [PATCH] i386 Time: Avoid PIT SMP lockups

[Maciej W. Rozycki]

On Wed, 11 Oct 2006, Andrew Morton wrote:

> So this patch has the potential to screw up people who have 2-way or 4-way,
> no hpet/pm-timer and dodgy TSCs.

 Note that all APIC-based SMP systems (even these rare i486 beasts) by 
definition do have local APIC timers, one per CPU, with a reasonable 
resolution which could likely be used instead.  There is an erratum in 
some early Pentium integrated APICs, where a tick is lost when 0 is 
reached (the timer counts downwards), so it may be needed to be taken into 
account for good timekeeping, but otherwise the timers look like a 
reasonable choice.  The timers are local to their respective CPUs and are 
never written by Linux (see references to APIC_TMCCT), so there is no need 
for locking to access them.

  Maciej
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