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Re: [gpsd-dev] PPS and privilege-dropping
From: |
Eric S. Raymond |
Subject: |
Re: [gpsd-dev] PPS and privilege-dropping |
Date: |
Fri, 18 Oct 2013 15:54:50 -0400 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
Gary E. Miller <address@hidden>:
> But that is the bug, you can not have a JSON emitter in the PPS thread!
I've fixed the problem. The right thing to do is to put a mutex
exclusion around the one socket send(2) that's used for all JSON
writes to clients; the function is throttled_write() in gpsd.c. Now,
no matter how control arrives there, no two of those sends while be
able to fire at once. No more garbled output.
The really annoying thing is that I had done this before and it
worked. Then I forgot why there was an exclusion around the send, and
*removed* it.
/me facepalms
Thankfully this was after 3.9, so the bad code never shipped for
production.
> > The content of the report is a different issue. You have implied
> > that the data in it is misleading; I want to know why you think that
> > and, if required, fix it. (See "representation of domain" below.)
>
> It is not using the right time structures. I'll fix it.
OK.
> > That's not enough by itself. You and other time nuts have implicit
> > knowledge, expressed in jargon like "chimers" which isn't actually
> > defined anywhere (I googled to check). We need to get that knowledge
> > onto (virtual) paper.
>
> Odd, I can't find a trvial reference to that either. A chimer is just
> an time source you are using. Likely remote in some
You said something I found full of implications: "Basically you get several
good chimers and adjust fudges until they all agree."
I have a feeling that if I really understood that I would grok the
whole tuning process. Can you unpack that into a paragraph, focusing
on how you *tell* when your chimers agree?
It sounds like a "fudge" is your estimate of the propagation delay
from the chimer, is that right?
--
<a href="http://www.catb.org/~esr/">Eric S. Raymond</a>
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- Re: [gpsd-dev] PPS and privilege-dropping, (continued)
- Re: [gpsd-dev] PPS and privilege-dropping, Gary E. Miller, 2013/10/17
- Re: [gpsd-dev] PPS and privilege-dropping, Gary E. Miller, 2013/10/18
- Re: [gpsd-dev] PPS and privilege-dropping, Eric S. Raymond, 2013/10/18
- Re: [gpsd-dev] PPS and privilege-dropping, Gary E. Miller, 2013/10/18
- Re: [gpsd-dev] PPS and privilege-dropping, Eric S. Raymond, 2013/10/18
- Re: [gpsd-dev] PPS and privilege-dropping, Gary E. Miller, 2013/10/17
- Re: [gpsd-dev] PPS and privilege-dropping, Eric S. Raymond, 2013/10/17
- Re: [gpsd-dev] PPS and privilege-dropping, Gary E. Miller, 2013/10/18
- Re: [gpsd-dev] PPS and privilege-dropping, Eric S. Raymond, 2013/10/18
- Re: [gpsd-dev] PPS and privilege-dropping, Gary E. Miller, 2013/10/18
- Re: [gpsd-dev] PPS and privilege-dropping,
Eric S. Raymond <=
- Re: [gpsd-dev] PPS and privilege-dropping, Gary E. Miller, 2013/10/18
- Re: [gpsd-dev] PPS and privilege-dropping, Greg Troxel, 2013/10/18
- Re: [gpsd-dev] PPS and privilege-dropping, Gary E. Miller, 2013/10/18
- Re: [gpsd-dev] PPS and privilege-dropping, Eric S. Raymond, 2013/10/19
- Re: [gpsd-dev] PPS and privilege-dropping, Eric S. Raymond, 2013/10/19
- Re: [gpsd-dev] PPS and privilege-dropping, Greg Troxel, 2013/10/18
- Re: [gpsd-dev] PPS and privilege-dropping, Gary E. Miller, 2013/10/18
- Re: [gpsd-dev] PPS and privilege-dropping, Greg Troxel, 2013/10/18
- Re: [gpsd-dev] PPS and privilege-dropping, Hal Murray, 2013/10/18
- Re: [gpsd-dev] PPS and privilege-dropping, Gary E. Miller, 2013/10/18