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Re: [PATCH 1/2] daemon: use timeout for uninterruptible poll




Junio C Hamano <gitster@xxxxxxxxx> writes:

> I think you identified the problem and diagnosed it correctly, but I
> find that the change proposed here introduces a severe layering
> violation.  The code is still calling what is called poll(), which
> should not have such a broken semantics.

I only mentioned a piece of fact (i.e. "the code calls poll() after
the patch"), but I guess I should have made it clear what makes that
a bad thing.  Future readers of the code in daemon.c are required to
be aware of the limitation of some poll() emulation; they cannot
"optimize" out and made the code unware of the (non-)existence of
remaining children, for example.  When the callsite uses poll(),
those who know how poll() ought to work won't be.  The reason why
the xpoll() I mentioned as a possible alternative would be better is
because they will learn why we do not use normal poll() there and
why we maintain and pass live_children (and those who cut and paste
without understanding the existing code _will_ copy the calling site
of xpoll(), which will automatically copy the need to maintain the
number of remaining children ;-).