Re: Postmaster crashed during start

Srinath Reddy <srinath2133(at)gmail(dot)com> writes:
> when we kill postmaster using kill -9 and start immediately it crashes with
>> FATAL: pre-existing shared memory block (key 2495405, ID 360501) is still
>> in use

"Doctor, it hurts when I do this!"

"So don't do that!"

This is not a supported way of shutting down the postmaster, and it
never will be. Use SIGINT, or SIGQUIT if you are in a desperate
hurry and are willing to have the next startup take longer.

I think the specific reason you are seeing this is that it takes
nonzero time for the postmaster's orphaned child processes to
notice that the postmaster is gone and terminate. As long as
any of those children remain, the shared memory block will have
a nonzero reference count. The new postmaster sees that and
refuses to start, for the very sound reason that it risks
data corruption if it brings up a new set of worker processes
while any of the old ones are still running.

regards, tom lane