From: Tomasz Zielonka <tomek@mult.i.pl>
To: PostgreSQL bugs <pgsql-bugs@postgresql.org>
Date: Mon, 3 Sep 2001 06:55:57 +0200
Mail-Followup-To: Tomasz Zielonka <tomek@mult.i.pl>,	PostgreSQL bugs <pgsql-bugs@postgresql.org>
User-Agent: Mutt/1.2i

Hi!

Platform: PostgreSQL 7.1.3, Linux 2.4.8, egcs 2.91.66

PostgreSQL forgets to release lock until shutdown in this scenario:

CREATE TABLE dummy (X integer);


session1                       session2
------------------------------------------------------------
BEGIN;                       |
                             |BEGIN;
SELECT * FROM dummy;         |
                             |SELECT * FROM dummy;
LOCK TABLE dummy;            |
                             |LOCK TABLE dummy;
                              deadlock....                 
\q                            \q

Deadlock is OK here, but I can't access dummy table until I restart postmaster

Subject: Re: [BUGS] Error in backend/storage/lmgr/proc.c: ProcSleep() 
From: Tom Lane <tgl@sss.pgh.pa.us>
To: Tomasz Zielonka <tomek@mult.i.pl>
cc: PostgreSQL bugs <pgsql-bugs@postgresql.org>
Date: Mon, 03 Sep 2001 22:37:11 -0400
Comments: In-reply-to Tomasz Zielonka <tomek@mult.i.pl>	message dated "Mon, 03 Sep 2001 06:55:57 +0200"

Tomasz Zielonka <tomek@mult.i.pl> writes:
> Platform: PostgreSQL 7.1.3, Linux 2.4.8, egcs 2.91.66
> PostgreSQL forgets to release lock until shutdown in this scenario:

Good catch!  This has been broken since 7.1 ... surprising that no one
discovered the problem sooner.

I think that rather than removing the early-deadlock-detection code as
you suggest, it's better to make it work correctly.  I have applied a
patch that allows RemoveFromWaitQueue() to be used, so that the recovery
path is the same as if HandleDeadLock had been invoked.

			regards, tom lane