The default Linux behaviour on an NMI of either memory or unknown is to continue operation. For many environments such as scientific computing it is preferable that the box is taken out and the error dealt with than an uncorrected parity/ECC error get propagated.
A small number of systems do generate NMI’s for bizarre random reasons such as power management so the default is off. That sysctl works like the existing panic controls already in that directory.
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