| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> |
| Cc: | Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: SSI atomic commit |
| Date: | 2011-07-05 18:16:20 |
| Message-ID: | 21785.1309889780@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> writes:
> Hmm, I think it would be simpler to decide that instead of
> SerializableXactHashLock, you must hold ProcArrayLock to access
> LastSxactCommitSeqNo, and move the assignment of commitSeqNo to
> ProcArrayTransaction(). It's probably easiest to move
> LastSxactCommitSeqno to ShmemVariableCache too. There's a few places
> that would then need to acquire ProcArrayLock to read
> LastSxactCommitSeqno, but I feel it might still be much simpler that way.
Yeah ... this patch creats the need to hold both
SerializableXactHashLock and ProcArrayLock during transaction commit,
which is a bit scary from a deadlock-risk perspective, and not pleasant
from the concurrency standpoint either. It'd be better to push some
functionality into the procarray code.
regards, tom lane
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