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Date: Wed, 14 Jun 2017 22:04:00 -0700
From: Gleb Smirnoff <glebius@FreeBSD.org>
To: Konstantin Belousov <kostikbel@gmail.com>
Cc: src-committers@freebsd.org, svn-src-all@freebsd.org,
 svn-src-head@freebsd.org
Subject: Re: svn commit: r319874 - head/sys/kern
Message-ID: <20170615050400.GP50023@FreeBSD.org>
References: <201706122111.v5CLBBUT092606@repo.freebsd.org>
 <20170612234356.GD50023@FreeBSD.org>
 <20170613120643.GX2088@kib.kiev.ua>
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On Tue, Jun 13, 2017 at 03:06:43PM +0300, Konstantin Belousov wrote:
K> On Mon, Jun 12, 2017 at 04:43:56PM -0700, Gleb Smirnoff wrote:
K> > On Mon, Jun 12, 2017 at 09:11:11PM +0000, Konstantin Belousov wrote:
K> > K> Author: kib
K> > K> Date: Mon Jun 12 21:11:11 2017
K> > K> New Revision: 319874
K> > K> URL: https://svnweb.freebsd.org/changeset/base/319874
K> > K> 
K> > K> Log:
K> > K>   Print unimplemented syscall number to the ctty on SIGSYS, if enabled
K> > K>   by the knob kern.lognosys.
K> > 
K> > Why is it off by default?
K> In some (non-default) situation it may cause lot of ctty output.
K> I made the knob tunable to allow it to be set very early (init)
K> if needed.

I remember myself being a beginner UNIX user, and all this
"bad system call, core dumped" messages were so annoyingly
uninformative for me, and I had no idea how to track to the
actual problem. This feature gives a lot of clue for a beginner
user, but having it default to off, devaluates its value.

To avoid possible tty spam for an application that produces ton
of bad syscalls, but ignores SIGSYS, we can enable the feature
for those processes, who doesn't ignore SIGSYS.

-- 
Totus tuus, Glebius.