When are machine checks suppose to be recoverable?

David Woodhouse dwmw2 at infradead.org
Wed Aug 24 02:43:14 EST 2005

On Mon, 2005-08-22 at 23:56 -0300, Marcelo Tosatti wrote:
> "My dual G4 PowerMac crashes sometimes when it probes for the (absent)
> serial ports. Theoretically it's supposed to take a machine check and
> recover -- but it doesn't always work like that."
> Maybe you just need the proper entry in the exception table for IO
> inb/outb?
> Is there a stacktrace, David?

No, just a silent death when probing for one of the serial ports;
usually not the first. It doesn't seem to even make it into the machine
check handler. Adding printks into serial_inb and serial_outb makes it
much less likely to happen -- could be something bizarre about alignment
of the instructions which cause the machine check, or time elapsed from
one machine check to the next.


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