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Re: [HACKERS] postgres under gdb

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Chris <chris(at)bitmead(dot)com>, pgsql-hackers(at)postgreSQL(dot)org
Subject: Re: [HACKERS] postgres under gdb
Date: 2000-01-28 17:30:34
Message-ID: 200001281730.MAA29436@candle.pha.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
> Chris <chris(at)bitmead(dot)com> writes:
> > How do you run postgres under gdb?
> 
> If you are running a standalone backend, you just fire it up.
> For normal use under a postmaster, the easiest thing I've found is to
> start psql (or your favorite client) in one window, start gdb on the
> postgres executable in another, and then "attach" to the already-started
> backend process.  (Use "ps" to discover the backend's PID.)  You must
> run gdb as postgres, of course, but the client process can belong to
> anyone.
> 
> It gets a little tricky if you are trying to debug part of the
> backend startup sequence.  We have a kluge for that: start psql
> with PGOPTIONS="-W n".  That causes the backend to sleep() for n
> seconds fairly early in its startup, giving you time to attach to it
> before anything really interesting happens.
> 
> In theory you can debug one backend in a live production system
> this way, but I wouldn't recommend doing that except in dire need.
> If you use gdb to stop the backend while it is holding a lock, you'll
> block other backends too --- and holding a spinlock is even worse,
> because those other backends will time out after a minute or so.
> Better to use a playpen installation.
> 
> (Hey Bruce, shouldn't this info be in FAQ_DEV?)

Yes, let me add it.

-- 
  Bruce Momjian                        |  http://www.op.net/~candle
  pgman(at)candle(dot)pha(dot)pa(dot)us               |  (610) 853-3000
  +  If your life is a hard drive,     |  830 Blythe Avenue
  +  Christ can be your backup.        |  Drexel Hill, Pennsylvania 19026

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