[TUHS] signals and blocked in I/O

Larry McVoy lm at mcvoy.com
Sat Dec 2 02:18:10 AEST 2017

On Fri, Dec 01, 2017 at 11:11:56AM -0500, Clem Cole wrote:
> It's hard because if I/O (like DMA) is in progress, what are the proper
> semantics to exit/roll back?   When do you stop the transfer and what
> happens.   When doing direct to/from disk (like a in a real-time system),
> this can get tricky.

So at first blush, what it seems like is you need a barrier to starting more
DMA's.  You take the signal, the signal changes state to say to the I/O
system "finish what you are doing but then no more".

Or what you do is kill the process, tear down all of the pages except those
that are locked for I/O, leave those in the process and wait for the I/O to
get done.  That might be simpler.

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