I have an embedded application for the RPi-3.  Unfortunately it's likely that
uses will remove power without properly shutting the RPi down.  Therefore I've
got a 'power-going-down' bit of hardware which sets a GPIO bit causing a proper
shutdown.  The question, of course, is how long does a shutdown take?  I'm
trying to ensure that the flash program/OS memory does not get corrupted.  I've
got a lower bound on this time by running a program that toggles another GPIO
bit,
and seeing when that stops vs. the time when I toggle the shutdown bit; but
presumably other things could take more time.

Running the current Raspbian.

   TIA!
   -F

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