Re: Hot Standy introduced problem with query cancel behavior

On Thursday 07 January 2010 19:49:59 Tom Lane wrote:
> Andres Freund <andres(at)anarazel(dot)de> writes:
> > Stupid question:
> >
> > Why dont we add CHECK_FOR_INTERRUPTS (or something similar) to everything
> > calling recv (especially in the EINTR) case?
>
> We pretty much have CHECK_FOR_INTERRUPTS everywhere that it's safe
> already. The problem here is not a lack of execution of
> CHECK_FOR_INTERRUPTS, but what to do inside it. Although I pointed to
> an interrupt service routine as being the worst case, the fact is that
> Simon's code will crash the system in a large number of scenarios even
> when ProcessInterrupts is called from CHECK_FOR_INTERRUPTS rather than
> directly from the signal handler.
I did not want to suggest using Simons code there. Sorry for the brevity.

The reason I suggested adding CHECK_FOR_INTERRUPTS into the recv code path was
that it should allow a relatively "natural" handling of canceling "IDLE IN
TRANSACTION" queries without doing anything in the interrupt handler.

I think it shouldn't be to hard to make that code path safe for
CHECK_FOR_INTERRUPTS().

I personally don't think its important to be that nice to a non-cooperating
backend (i.e. one catching our ERRORs) so I dont see any problems in just
FATAL'ing it after a couple of tries (the code retries already so...).

Andres