Re: "stuck spinlock"

Christophe Pettus <xof(at)thebuild(dot)com> writes:
> Immediately after an upgrade from 9.3.1 to 9.3.2, we have a client getting frequent (hourly) errors of the form:

> /var/lib/postgresql/9.3/main/pg_log/postgresql-2013-12-12_211710.csv:2013-12-12 21:40:10.328 UTC,"n","n",32376,"10.2.1.142:52451",52aa24eb.7e78,5,"SELECT",2013-12-12 21:04:43 UTC,9/7178,0,PANIC,XX000,"stuck spinlock (0x7f7df94672f4) detected at /tmp/buildd/postgresql-9.3-9.3.2/build/../src/backend/storage/buffer/bufmgr.c:1099",,,,,,"<redacted>"

> uname -a: Linux postgresql3-master 3.8.0-33-generic #48~precise1-Ubuntu SMP Thu Oct 24 16:28:06 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux.

> Generally, there's no core file (which is currently enable), as the postmaster just normally exits the backend.

Hm, a PANIC really ought to result in a core file. You sure you don't
have that disabled (perhaps via a ulimit setting)?

As for the root cause, it's hard to say. The file/line number says it's
a buffer header lock that's stuck. I rechecked all the places that lock
buffer headers, and all of them have very short code paths to the
corresponding unlock, so there's no obvious explanation how this could
happen.

regards, tom lane