Re: [patch] fix per-CPU MCA mess and make UP kernels work again

From: Russ Anderson <rja_at_sgi.com>
Date: 2005-02-05 03:34:48
Jack Steiner wrote:
> On Fri, Feb 04, 2005 at 02:00:15PM +1100, Keith Owens wrote:
> 
> To further muddy the waters, it looks like the latest Error Handling Guide
> has addressed the issue:
> 
> >> IntelĀ® ItaniumĀ® Processor Family Error Handling Guide April 2004
> >>
> >> Document Number: 249278-003
> >>
> >> 2.7.1
> >>
> >> ...
> >> The MCA error information is provided to the OS_MCA layer. The MCA
> >> error record is logged to the NVM.  To simplify SAL implementation, it
> >> is strongly recommended that SAL process all MCAs by handing off to the
> >> OS as soon as possible to prevent some OSes from experiencing time-outs
> >> and potentially crashing the system. >>>> The SAL may maintain a variable in
> >> the SAL data area that indicates whether SAL, on one of the processors,
> >> is already handling an MCA. If so, MCA processing on other processors will
> >> wait within the SAL MCA handler until the current MCA is processed. This
> >> situation may arise when local MCAs are experienced on multiple
> >> processors. <<<<<<<
> 
> 
> However, it says "may maintain a variable...".  Should I interpret this as 
> allowing but not requiring serialization?

I vote for that interpritation.  IMHO, Linux needs to continue to support
SALs that single thread MCAs, but should also allow concurrent MCA
handling for SALs that support it.


-- 
Russ Anderson, OS RAS/Partitioning Project Lead  
SGI - Silicon Graphics Inc          rja@sgi.com
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Received on Fri Feb 4 11:36:11 2005

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