Re: kill -KILL: What happens?

Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On Thu, Jan 13, 2011 at 2:45 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> I wonder whether we could have some sort of latch-like counter that
>> would count the number of active backends and deliver signals when the
>> count went to zero. However, if the goal is to defend against random
>> applications of SIGKILL, there's probably no way to make this reliable
>> in userspace.

> I don't think you can get there 100%. We could, however, make a rule
> that when a background process fails a PostmasterIsAlive() check, it
> sends SIGQUIT to everyone it can find in the ProcArray, which would at
> least ensure a timely exit in most real-world cases.

You're going in the wrong direction there: we're trying to have the
system remain sane when the postmaster crashes, not see how quickly
it can screw up every remaining session.

BTW, in Unix-land we could maybe rely on SysV semaphores' SEM_UNDO
feature to keep a trustworthy count of how many live processes there
are. But I don't know whether there's anything comparable for Windows.

regards, tom lane