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Re: Periodic freezing of backend processes

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Andrew McMillan <Andrew(at)catalyst(dot)net(dot)nz>
Cc: PostgreSQL Bugs <pgsql-bugs(at)postgresql(dot)org>
Subject: Re: Periodic freezing of backend processes
Date: 2000-07-09 17:44:26
Message-ID: 29100.963164666@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-bugs
Andrew McMillan <Andrew(at)catalyst(dot)net(dot)nz> writes:
> I am finding that I periodically have a backend process just 'freeze' on
> me.

Needs to be looked at, for sure.

> What can I do to tickle the backend processes to get it to tell me where
> it is at?

What I'd do is attach to it with gdb and poke around.

	gdb path-of-postgres-executable
	attach PID-of-target-process
	bt
	...

It helps if you've compiled the backend with -g.  It might also be
useful to enable Asserts.

> I have found that if I kill the backend process that is locked up, then
> do exactly the same query, it locks up again.  BUT if I shut down and
> restart the postmaster and then do exactly the same query (reload my web
> page, in fact) the response is immediate again.

Sounds like the problem is associated with some particular configuration
of shared memory.  Perhaps some prior query has failed to release a
lock, or some such?

			regards, tom lane

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