On 2019-04-12 11:49 AM, Warner Losh wrote:
On Fri, Apr 12, 2019 at 9:39 AM Brooks Harris <[email protected]
<mailto:[email protected]>> wrote:
Hopefully Linux will follow suit in some manner. This might be
accompanied with updating POSIX time in some manner to support Leap
Seconds..
The last 20 attempts to do that have failed, sadly. time_t is quite
pervasive and has a significant amount of both legacy code (which
could mostly be dealt with by transitioning to new interfaces, but not
entirely ushering in a new class of off by 37s bugs) but also it's
stored in a number of places that are impossible to change (timestamps
in legacy filesystems).
I agree. Its in the file system timestamps where much of the challenge
lies. There is insufficient metadata stored in the timestamps, both
Linux and Windows NTFS, always has been. Its unclear to me if Microsoft
intends to extend NTFS to support their new system. It seems like they
must if they expect it to be reasonably traceable. As I understand it,
as it is now, the relevant metadata information would need to be
collected from elsewhere in the local operating system to make sense of
an NTFS timestamp. That metadata may not be available to other systems
attempting to interpret an NTFS timestamp. It really needs to reside in
the timestamp itself, including local time metadata.
It's relatively easy to mostly get the get/set time interfaces to
allow for leap seconds, but the data storage problem is a hassle.
Also, since the legacy interfaces don't really have leap seconds in
them at all, you still have all the hassles of repeating times for
code that's not been updated.
Yes. It seems infeasible to me that the enormous number of applications
that assume 86400 secs per day (including the widely used legacy
Gregorian calendar without Leap Seconds) can be updated to some new, as
yet un-proposed Leap Second aware specification.
Its unclear to me how Microsoft intends to approach that challenge.
Perhaps by updating all Microsoft applications, like .NET, Office, SQL
Server, etc, etc, etc.? Oh man, that just seems an unreasonably huge
project, and then how would any of it interact with legacy systems and
other operating systems? And email, and iCalendar, etc, etc.? And all
the timekeeping tools in all the programming languages? How in the world
could that happen?
While I applaud Microsoft for strong-arming these changes through (and
taking the huge amount of time to chase down all the API
implications), there's no such driving force in Linux, BSD or any of
the other Unixes, with the possible exception of Apple and ios/osx.
Google + android might be able to get away with a change here, should
Google decide to cope, but since they already just smear I doubt the
idea would get enough traction to get the proper level of commitment
organizationally to make it happen.
The challenge may be put upon them by new financial regulations.
Microsoft can now claim compliance, a potentially huge competitive
advantage for Windows and Azure over the other OSs and cloud
deployments, especially in financial sectors, banking, transactions,
etc. Now how this is going to propagate internet, browsers, Java, and
your shopping basket?
And, as always, I'd love for someone to do all the work and prove my
jaded cynicism wrong.
It looks like a heavy lift to me too.
-Brooks
Warner
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