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Date:      Wed, 29 Feb 2012 09:36:02 -0500
From:      John Baldwin <jhb@freebsd.org>
To:        Konstantin Belousov <kostikbel@gmail.com>
Cc:        src-committers@freebsd.org, Pawel Jakub Dawidek <pjd@freebsd.org>, svn-src-all@freebsd.org, Mikolaj Golub <trociny@freebsd.org>, "Robert N. M. Watson" <rwatson@freebsd.org>, svn-src-head@freebsd.org, Julian Elischer <julian@freebsd.org>
Subject:   Re: svn commit: r232181 - in head/sys: kern sys
Message-ID:  <201202290936.02309.jhb@freebsd.org>
In-Reply-To: <20120229132507.GB55074@deviant.kiev.zoral.com.ua>
References:  <201202261425.q1QEPm9g069102@svn.freebsd.org> <86mx81byt6.fsf@in138.ua3> <20120229132507.GB55074@deviant.kiev.zoral.com.ua>

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On Wednesday, February 29, 2012 8:25:07 am Konstantin Belousov wrote:
> On Wed, Feb 29, 2012 at 02:37:25PM +0200, Mikolaj Golub wrote:
> > 
> > On Wed, 29 Feb 2012 12:03:00 +0000 Robert N. M. Watson wrote:
> > 
> >  RNMW> I think the monitoring aspect of the patch is fine.
> > 
> >  RNMW> The bit I was worried about was external umask changes. This can cause
> >  RNMW> race conditions for applications that manage their umask -- for
> >  RNMW> example, bsdtar, if I recall correctly. It's one thing to use a
> >  RNMW> debugger to force an application to change its umask -- the developer
> >  RNMW> needs to know they are changing application behaviour. But exposing a
> >  RNMW> feature that can lead to correct applications but incorrect results is
> >  RNMW> a risky thing to do, hence my objection.
> > 
> >  RNMW> I think given the other objections, it would be wise to remove write
> >  RNMW> access to process umasks, but retain read access for procstat (which is
> >  RNMW> quite useful, I agree).
> > 
> > I still don't see why having a sysctl RW is worse than asking users to run
> > something like in the attach when they need to change umask for another
> > process, but ok, if people don't like RW I will remove it.
> > 
> What is done is attach is much worse then the sysctl, just because
> debugger attach often causes spurious EINTR, indeed seriously disrupting
> applications, as opposed to some uncertain damage that could be done in
> theory.

kgdb doesn't though, and presumably for umask you would change it via kgdb, so
from the running process' perspective it would look the same as changing it via
sysctl.

-- 
John Baldwin



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