Re: [Qemu-devel] [RFC PATCH] main-loop: Unconditionally unlock iothread

[Paolo Bonzini]

Il 04/04/2013 01:58, Peter Crosthwaite ha scritto:
> 
> I think there may be a flaw in that "any of the descriptors being
> pollable" is not a good definition of progress. stdin is blocked by
> the fact that the device and mux cannot accept their data anymore so
> even though its readable, no meaningful read will happen. That leaves
> us with having to devise more elaborate code to define progress, or we
> simplify by just removing this nonblocking optimisation altogether
> (original patch).

If stdin is blocked, it shouldn't be polled at all.  That is the purpose
of the can_read callback.  Unfortunately, return FALSE from the prepare
callback still leaves the poll handler.

So your original patch fixes the symptom, but leaves the busy waiting
unfixed.

The right thing to use would be g_source_add_child_source() and
g_source_remove_child_source(), but that is only present since glib 2.28
and we currently require 2.12 (2.20 on Windows).

Anthony, Amit, can you look at it?

Paolo