Re: missing LockBuffer(buffer, BUFFER_LOCK_SHARE) in trigger.c GetTupleForTrigger?

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Andres Freund <andres(at)2ndquadrant(dot)com>
Cc: Simon Riggs <simon(at)2ndquadrant(dot)com>, Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: missing LockBuffer(buffer, BUFFER_LOCK_SHARE) in trigger.c GetTupleForTrigger?
Date: 2012-11-30 19:16:47
Message-ID: 21640.1354303007@sss.pgh.pa.us
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Andres Freund <andres(at)2ndquadrant(dot)com> writes:
> On 2012-11-30 14:08:05 -0500, Tom Lane wrote:
>> BTW, I went looking for other places that might have a similar mistake.
>> I found that contrib/pageinspect/btreefuncs.c pokes around in btree
>> pages without any buffer lock, which seems pretty broken --- don't we
>> want it to take share lock?

> I seem to remember comments somewhere indicating that pageinspect (?)
> doesn't take locks by intention to make debugging of locking problems
> easier. Not sure whether thats really realistic, but ...

Dunno, that seems like a pretty lame argument when compared to the very
real possibility of crashing due to processing corrupt data. Besides,
the heap-page examination functions in the same module take buffer lock,
so why shouldn't these?

regards, tom lane

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