Re: [PATCH v3] x86/mce: Try printing all machine check banks known before panic

From: Borislav Petkov
Date: Fri Nov 21 2014 - 11:41:49 EST

On Fri, Nov 21, 2014 at 09:20:59AM +0800, rui wang wrote:
> We've found there are cases after mce_log() has been called, we then
> decide to panic, but print_mce() can't find anything in the mcelog
> buffer. I think the mcelog buffer can be consumed by the user space
> daemon (possibly on a different CPU). We may end up seeing the "panic
> from unknown source" message without printing any mca banks, which is
> one of the cases where this bug was originated.

Ok, so modify the mcelog buffer to not zero out its entries when they're
being read out in userspace through mce_chrdev_read() but simply to
leave them in. Then you can read them out again on panic time. The mce
log buffer will have to become a circular buffer or something like that.


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