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Date:      Wed, 28 Nov 2012 18:13:41 +0000 (GMT)
From:      Robert Watson <rwatson@FreeBSD.org>
To:        Alfred Perlstein <bright@mu.org>
Cc:        svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org, Andre Oppermann <andre@freebsd.org>, Peter Wemm <peter@wemm.org>
Subject:   Re: svn commit: r243627 - head/sys/kern
Message-ID:  <alpine.BSF.2.00.1211281810190.91531@fledge.watson.org>
In-Reply-To: <50B64C43.50001@mu.org>
References:  <201211272004.qARK4qS8047209@svn.freebsd.org> <CAGE5yCpxOdsjefe6quR_gjs82pk9a2e_H_WUNUWhUGA3WZPJaw@mail.gmail.com> <50B54180.5020608@freebsd.org> <alpine.BSF.2.00.1211272246560.37292@fledge.watson.org> <50B54492.5040100@freebsd.org> <956CE44A-BA0F-4FE4-AA38-F4B90C85ECBA@FreeBSD.org> <50B54CE0.6080008@freebsd.org> <2A12C740-1D72-4D30-B663-47A37AAC2FF3@FreeBSD.org> <50B5C4F1.1020002@freebsd.org> <50B64C43.50001@mu.org>

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On Wed, 28 Nov 2012, Alfred Perlstein wrote:

>> Yes, and I didn't really expect you to answer (at least quickly) during 
>> your FreeBSD hiatus.  So it was seeking review by chance.
>> 
>> Alas I found and fixed the bug myself within 2.5hrs.  While not optimal, a 
>> sign of poor prior testing and too much trust into the submitter of the 
>> patch it wasn't an earth shattering event.  Doesn't distract from the fact 
>> that it was mea culpa in any case though.
>> 
>> For prior review of kern_socket* and netinet/tcp_* related changes it has 
>> been on and off by various committers over the past year.  If we do have a 
>> policy of prior review required then it should be made official and 
>> codified in MAINTAINERS and universally applied to all.
>> 
> Personally I don't think we need any more anchors attached to people's feet 
> when developing FreeBSD.
>
> Mistakes will happen, they will happen in head.  Slowing down the process to 
> eliminate mistakes only works to slow down change and give a false sense of 
> "fixing stability" when in fact the only thing "stable" is the slowness of 
> submitting code.

Yes, the purpose of review in this case would not be to catch (too many) dumb 
mistakes -- that's what testing is for -- but rather, to introduce 
architectural review and catch quite subtle mistakes.  It was interesting 
doing the development cycle for the pcbgroup work a year or so ago -- having 
Bjoern do line-by-line reviews of changes generated not only lots of bug 
fixes, but also lots of high-level feedback on the design that improved it 
markedly.

"MAINTAINERS" is a concept I'd like to see die, but the idea of seeking 
pre-commit review for changes, especially in sensitive code, is something to 
encourage.  One reason review is so critical in this area is that there are 
lots of subtle implications to do with timing, object life cycles, inter-layer 
locking, etc, in the socket and TCP code -- things that any one author may not 
see the big picture on.  We've been working to improve comments, but the 
problem there, of course, is that you end up with a book of design comments, 
and code review actually brings many of those concerns to light in a more 
structured and practical way.

Robert



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