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Thread: Strange error message

Strange error message

From
Adriaan Joubert
Date:
Hi,
   we've suddenly started getting this error message out of postgres
(7.0.2). Does anybody know where it comes from?

ERROR:  UNLockBuffer: buffer 0 is not locked

Any help appreciated,

Adriaan

Re: Strange error message

From
Tom Lane
Date:
Adriaan Joubert <a.joubert@albourne.com> writes:
>     we've suddenly started getting this error message out of postgres
> (7.0.2). Does anybody know where it comes from?

> ERROR:  UNLockBuffer: buffer 0 is not locked

Evidently something is passing an invalid buffer number to LockBuffer
in src/backend/storage/buffer/bufmgr.c.  (0 is InvalidBuffer, but
LockBuffer won't notice that unless you compiled with asserts enabled.)
Whatever the bug is, it's not directly LockBuffer's fault.

What exactly are you doing that provokes this message?
        regards, tom lane

Re: Strange error message

From
Adriaan Joubert
Date:
Tom Lane wrote:

> Adriaan Joubert <a.joubert@albourne.com> writes:
> >     we've suddenly started getting this error message out of postgres
> > (7.0.2). Does anybody know where it comes from?
>
> > ERROR:  UNLockBuffer: buffer 0 is not locked
>
> Evidently something is passing an invalid buffer number to LockBuffer
> in src/backend/storage/buffer/bufmgr.c.  (0 is InvalidBuffer, but
> LockBuffer won't notice that unless you compiled with asserts enabled.)
> Whatever the bug is, it's not directly LockBuffer's fault.

Right, I'vebuilt a new database and everything seemed fine for a while and
now I've got this message back. It is due to the index on one of our
tables getting messed up - at least, if we drop and recreate the index
everything is fine. What should I do to track down what is happening?
Compile with asserts, or run with specific logging? Any advice
appreciated!

Adriaan

Re: Strange error message

From
Tom Lane
Date:
Adriaan Joubert <a.joubert@albourne.com> writes:
>>>> ERROR:  UNLockBuffer: buffer 0 is not locked

> Right, I'vebuilt a new database and everything seemed fine for a while and
> now I've got this message back. It is due to the index on one of our
> tables getting messed up - at least, if we drop and recreate the index
> everything is fine. What should I do to track down what is happening?
> Compile with asserts, or run with specific logging?

Compile with asserts and -g, and get a backtrace from the ensuing
coredump.  (LockBuffer *will* Assert when passed a zero.  If we are
really lucky, we might see an earlier Assert failure that will give
more clue about where the zero comes from --- but if not, the backtrace
from the bogus LockBuffer call might still be useful.)
        regards, tom lane