Re: [PATCHES] Win32 CHECK_FOR_INTERRUPTS() performance

[Qingqing Zhou <zhouqq(at)cs(dot)toronto(dot)edu>]

On Sun, 23 Oct 2005, Tom Lane wrote:

> "Magnus Hagander" <mha(at)sollentuna(dot)net> writes:
>
> In the spirit of incremental improvement ... I've taken Magnus' version
> and added the proposed change to re-enable Qingqing's patch by skipping
> WaitForSingleObjectEx altogether in the CHECK_FOR_INTERRUPTS code path.
> I also removed WaitForSingleObjectEx in pgwin32_poll_signals(), which
> AFAICS should be just like CHECK_FOR_INTERRUPTS.  I think this is what
> we are proposing to actually apply to 8.1beta4.  I can't test it though,
> so please check it over...
>
Questions:

Are we asserting that

	UNBLOCKED_SIGNAL_QUEUE() != 0
	then
	WaitForSingleObjectEx(0)==WAIT_OBJECT_0

If so, we can put this assertion in. Seems there is some race. In
pg_queue_signal(), we do it like this:

enter_critical_section();
mask the signal;
leave_critical_section();
SetEvent();

That is, we may detect the value first before we got event. So at least
the above assertion is not correct. This may cause other problems, just
for a quick feedback.

Regards,
Qingqing