Re: semop hanging - Postgres 9.4.4

On Tue, Dec 15, 2015 at 1:34 PM, Michał Nowak <minowack@wp.pl> wrote:

> postgres=# select version();
>                                                version
> ------------------------------------------------------------------------------------------------------
>  PostgreSQL 9.4.4 on x86_64-unknown-linux-gnu, compiled by gcc (Ubuntu 4.8.2-19ubuntu1) 4.8.2, 64-bit

There is a bug fix in 9.4.5 which can cause a deadlock on
lightweight locking.

http://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=bab959906911c97437f410a03b0346e6dd28d528

http://www.postgresql.org/support/versioning/

From a subsequent post:

> perf top:
>
>   17.04%  postgres                 [.] _bt_moveright
>   13.39%  postgres                 [.] LWLockAcquire
 >   8.82%  postgres                 [.] LWLockRelease
 >   8.11%  postgres                 [.] _bt_checkpage

The perf top output suggests the possibility of a corrupted index,
causing an endless loop.

Can you get a few stack traces from "stuck" backends?

--
Kevin Grittner
EDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company