Comment patch for bgworker.c

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From: Jim Nasby <Jim(dot)Nasby(at)BlueTreble(dot)com>
To: Pg Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Comment patch for bgworker.c
Date: 2014-10-25 00:51:07
Message-ID: 544AF3FB.5000604@BlueTreble.com
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The comment for the BackgroundWorkerSlot structure tripped me up reviewing Robert's background worker patch; it made it clear that you need to use a memory barrier before setting in_use, but normally you'd never need to worry about that because RegisterDynamicBackgroundWorker() handles it for you. Patch adds a comment to that effect.
--
Jim Nasby, Data Architect, Blue Treble Consulting
Data in Trouble? Get it in Treble! http://BlueTreble.com

Attachment Content-Type Size
patch text/plain 810 bytes
From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com>
Cc: Pg Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Comment patch for bgworker.c
Date: 2015-02-02 13:49:38
Message-ID: CA+TgmoYkuN_ZTsROmqzDkAMpxbYvPKLNfV9-AGdD+qUUty76KA@mail.gmail.com
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On Fri, Oct 24, 2014 at 8:51 PM, Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com> wrote:
> The comment for the BackgroundWorkerSlot structure tripped me up reviewing
> Robert's background worker patch; it made it clear that you need to use a
> memory barrier before setting in_use, but normally you'd never need to worry
> about that because RegisterDynamicBackgroundWorker() handles it for you.
> Patch adds a comment to that effect.

I vote to reject this patch. I think it's explaining something that
doesn't really need to be explained, and shouldn't be explained like
this even if it does. It adds a comment that reads "Note that
RegisterDynamicBackgroundWorker() handles in_use correctly for you".
But the long block comment of which it is a part is entirely devoted
to explaining concerns internal to bgworker.c, from which I think it
should be inferred that all of the public APIs in that file handle all
of the things in that paragraph correctly (or are intended to,
anyway).

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

From: Jim Nasby <Jim(dot)Nasby(at)BlueTreble(dot)com>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Pg Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Comment patch for bgworker.c
Date: 2015-02-03 02:13:25
Message-ID: 54D02EC5.1030505@BlueTreble.com
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On 2/2/15 7:49 AM, Robert Haas wrote:
> On Fri, Oct 24, 2014 at 8:51 PM, Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com> wrote:
>> The comment for the BackgroundWorkerSlot structure tripped me up reviewing
>> Robert's background worker patch; it made it clear that you need to use a
>> memory barrier before setting in_use, but normally you'd never need to worry
>> about that because RegisterDynamicBackgroundWorker() handles it for you.
>> Patch adds a comment to that effect.
>
> I vote to reject this patch. I think it's explaining something that
> doesn't really need to be explained, and shouldn't be explained like
> this even if it does. It adds a comment that reads "Note that
> RegisterDynamicBackgroundWorker() handles in_use correctly for you".
> But the long block comment of which it is a part is entirely devoted
> to explaining concerns internal to bgworker.c, from which I think it
> should be inferred that all of the public APIs in that file handle all
> of the things in that paragraph correctly (or are intended to,
> anyway).

At this point I don't remember what it was in your patch that tripped me
up on this, so I'm marking the patch rejected.
--
Jim Nasby, Data Architect, Blue Treble Consulting
Data in Trouble? Get it in Treble! http://BlueTreble.com