In 8.2, shutdown wrongly caused automatic restart

Hi,

In my customer's system using v8.2.5, even though no process exited abnormally,
the fast shutdown wrongly caused the automatic restart of a database. The server
log is as follows:

Jul 18 16:21:51 postgres[26624]: [1-1] LOG: received fast shutdown request
Jul 18 16:21:51 postgres[26624]: [2-1] LOG: aborting any active transactions
Jul 18 16:21:51 postgres[3475]: [1-1] FATAL: terminating connection
due to administrator command
Jul 18 16:21:51 postgres[6978]: [1-1] FATAL: terminating connection
due to administrator command
Jul 18 16:21:51 postgres[30868]: [1-1] FATAL: terminating connection
due to administrator command
Jul 18 16:21:51 postgres[15980]: [1-1] FATAL: terminating connection
due to administrator command
Jul 18 16:21:51 postgres[27501]: [1-1] FATAL: terminating connection
due to administrator command
Jul 18 16:21:51 postgres[24341]: [1-1] FATAL: terminating connection
due to administrator command
Jul 18 16:21:51 postgres[28270]: [1-1] LOG: shutting down
Jul 18 16:21:51 postgres[28270]: [2-1] LOG: database system is shut down
Jul 18 16:21:53 postgres[11776]: [3-1] FATAL: the database system is
shutting down
Jul 18 16:21:53 postgres[11779]: [3-1] FATAL: the database system is
shutting down
Jul 18 16:21:53 postgres[11780]: [3-1] FATAL: the database system is
shutting down
Jul 18 16:21:53 postgres[11781]: [3-1] FATAL: the database system is
shutting down
Jul 18 16:21:53 postgres[26624]: [3-1] LOG: background writer
process (PID 28270) exited with exit code 0
Jul 18 16:22:01 postgres[26624]: [4-1] LOG: terminating any other
active server processes
Jul 18 16:22:04 postgres[26624]: [5-1] LOG: all server processes
terminated; reinitializing
Jul 18 16:22:07 postgres[11801]: [6-1] LOG: database system was shut
down at 2010-07-18 16:21:51 JST

As far as I read the source code, this problem seems to have happened
as follows.

1. After postmaster received SIGINT, it forcibly terminated all the backends.
2. After postmaster confirmed that no backend is running, it sent SIGUSR2 to
the bgwriter.
3. After the bgwriter received SIGUSR2, it started the shutdown checkpoint.
4. Postmaster accepted new connection from a client and forked new backend.
5. The bgwriter completed the checkpoint and ended normally before the backend
was rejected due to database state.
6. Now, the bgwriter had already ended even though there was a backend in
progress. Postmaster regarded this situation as abnormal and caused the
recovery.

In 8.3 or later, since postmaster doesn't regard that situation as abnormal
and just waits for all backends to exit again, the problem doesn't happen.
I think that this is a bug in 8.2 and should be fixed in the same way as 8.3
does. Thought?

Regards,

--
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center