RE: [PATCH] MCA recovery from memory read error caused by application

From: Luck, Tony <>
Date: 2004-02-20 16:29:33

Overall it looks quite good.  I think that I like
the pre-parsing the records to set up useful pointers
to make the rest of the code simpler.

A couple of specific code issues:

1) Looking at gr13 in the minstate area when you determined that the
MCA occurred in usermode will get you whatever value that the user
happened to have in r13 ... not the task structure.

2) Using "force_sig" in MCA context is probably going to violate some
locking rules.  I'm making this blanket statement without looking at
any code ... so I might be wrong ... but doing just about anything
in an MCA handler runs into locking problems :-( .

3) You need some code to clean the error from the page.
Otherwise the page will be freed when the process terminates,
and the next user will possibly hit the same error.

Now some general philosophical issues:

This implemention is making the assumption that errors are
soft ... i.e. that there is no permanent problem with the
memory when an error is reported.  More often than not this
assumption is true ... transient errors are more frequent
than hard failures.  But many RAS people prefer to err on
the side of paranoia, and might prefer to take the page with
the error out of service.

For future improvement ... you might want to special case
errors in user code pages.  These should be recoverable
with a page-fault like approach that re-reads the data
from the file, instead of killing the process.


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Received on Fri Feb 20 00:30:07 2004

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