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Re: [gpsd-dev] Updated docs on NTP segment management
From: |
Hal Murray |
Subject: |
Re: [gpsd-dev] Updated docs on NTP segment management |
Date: |
Wed, 18 Feb 2015 02:08:14 -0800 |
address@hidden said:
> I see no reason to make it not writeable by the client. So no need, yet,
> for a compatibility break.
The current setup doesn't work with more than one client. I can't run a
debugging monitor in parallel with ntpd.
It also simplifies security. If the client side is read-only, a layer of
attacks go away without any sysadmin setup complications.
-------
> Sadly read order can not be fixed on many architectures, like x86.
> So X and Y may have been flushed by the cache to main RAM, but not the data
> it is guarding.
I'm not a wizard on this area. I have worked with people who are. When I
asked one of them, he gave me that recipe. When I asked about cache flushes
and such, he said that x86 hardware does the right thing.
I think the actual code needs volatiles in the right places (so the compiler
will do the right thing) and a few memory barriers on some architectures.
Do you know of a good web page covering this area? I've looked before
without finding anything. I just tried again, this looks like great
background, but I haven't found the section that discusses specific
architectures.
Documentation/memory-barriers.txt
I think that's part of the kernel sources.
--
These are my opinions. I hate spam.
- Re: [gpsd-dev] Updated docs on NTP segment management, (continued)
- Re: [gpsd-dev] Updated docs on NTP segment management, Harlan Stenn, 2015/02/26
- Re: [gpsd-dev] Updated docs on NTP segment management, Gary E. Miller, 2015/02/26
- Re: [gpsd-dev] Updated docs on NTP segment management, Harlan Stenn, 2015/02/26
- Re: [gpsd-dev] Updated docs on NTP segment management, Gary E. Miller, 2015/02/26
- Re: [gpsd-dev] Updated docs on NTP segment management, Harlan Stenn, 2015/02/26
- Re: [gpsd-dev] Updated docs on NTP segment management, Gary E. Miller, 2015/02/25
- Re: [gpsd-dev] Updated docs on NTP segment management, Eric S. Raymond, 2015/02/25
- Re: [gpsd-dev] Updated docs on NTP segment management, Harlan Stenn, 2015/02/25
- Re: [gpsd-dev] Updated docs on NTP segment management, Eric S. Raymond, 2015/02/26
- Re: [gpsd-dev] Updated docs on NTP segment management, Hal Murray, 2015/02/28
- Re: [gpsd-dev] Updated docs on NTP segment management,
Hal Murray <=
- Re: [gpsd-dev] Updated docs on NTP segment management, Gary E. Miller, 2015/02/18
- Re: [gpsd-dev] Updated docs on NTP segment management, Harlan Stenn, 2015/02/18
- Re: [gpsd-dev] Updated docs on NTP segment management, Gary E. Miller, 2015/02/18