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Date:      Thu, 03 Oct 2019 15:24:06 +0000
From:      "Poul-Henning Kamp" <phk@phk.freebsd.dk>
To:        Warner Losh <imp@bsdimp.com>
Cc:        Konstantin Belousov <kostikbel@gmail.com>, Sebastian Huber <sebastian.huber@embedded-brains.de>, Bruce Evans <brde@optusnet.com.au>, FreeBSD <freebsd-hackers@freebsd.org>
Subject:   Re: Why is tc_get_timecount() called two times in tc_init()?
Message-ID:  <47834.1570116246@critter.freebsd.dk>
In-Reply-To: <CANCZdfpcOBJiYAKafhiWZS2g4vnLGVvzqhaOXetSSnU2Hj91nw@mail.gmail.com>
References:  <0e27fb3e-0f60-68e1-dbba-f17c3d91c332@embedded-brains.de> <20191002140040.GA44691@kib.kiev.ua> <20191003013314.O2151@besplex.bde.org> <20191002163946.GE44691@kib.kiev.ua> <20191003030837.C2787@besplex.bde.org> <20191003084021.GI44691@kib.kiev.ua> <CANCZdfpcOBJiYAKafhiWZS2g4vnLGVvzqhaOXetSSnU2Hj91nw@mail.gmail.com>

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--------
In message <CANCZdfpcOBJiYAKafhiWZS2g4vnLGVvzqhaOXetSSnU2Hj91nw@mail.gmail=
.com>
, Warner Losh writes:

>I think this is a good fix. I recall phk saying it was more paranoia for
>edge cases than really needed in a private email to me, but it's in the
>'gap' of email that I lost in a disk crash 12 years ago so I can't find i=
t
>for sure.

I think the original reason for this was (locked) delta-based
timecounters, (ie counters which roll over rapidly) in order that
their first "real" use would not return truly bogus values.

-- =

Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    =

Never attribute to malice what can adequately be explained by incompetence=
.



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