Write 100 times for tomorrow:
"Always print time_t as %jd, you never know what width it has"

Add a sysctl (default: off) which enables a log(LOG_INFO...) warning
if the clock is stepped.

Various minor details:
Give the HZ/overflow check a 10% margin.
Eliminate bogus newline.
If timecounters have equal quality, prefer higher frequency.

Some inspiration from: bde

Use the quality to disable timecounters for which we deem Hz too low.

bde made a number of suggested improvements to the code. This commit
represents the pruely stylistic changes and should have no net impact
on the rest of the code.

bde's more substantive changes wi

bde made a number of suggested improvements to the code. This commit
represents the pruely stylistic changes and should have no net impact
on the rest of the code.

bde's more substantive changes will follow in a separate commit once
we've come to closure on them.

Submitted by: bde

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Fix an extreme edge case in leap second handling. We need to call
ntp_update_second twice when we have a large step in case that step
goes across a scheduled leap second. The only way this could ha

Fix an extreme edge case in leap second handling. We need to call
ntp_update_second twice when we have a large step in case that step
goes across a scheduled leap second. The only way this could happen
would be if we didn't call tc_windup over the end of day on the day of
a leap second, which would only happen if timeouts were delayed for
seconds. While it is an edge case, it is an important one to get
right for my employer.

Sponsored by: Timing Solutions Corporation

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Give timecounters a numeric quality field.

A timecounter will be selected when registered if its quality is
not negative and no less than the current timecounters.

Add a sysctl to report all availa

Give timecounters a numeric quality field.

A timecounter will be selected when registered if its quality is
not negative and no less than the current timecounters.

Add a sysctl to report all available timecounters and their qualities.

Give the dummy timecounter a solid negative quality of minus a million.

Give the i8254 zero and the ACPI 1000.

The TSC gets 800, unless APM or SMP forces it negative.

Other timecounters default to zero quality and thereby retain current
selection behaviour.

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Remove extra space.

typo fix in comment.

Fix leap second processing by the kernel time keeping routines.
Before, we would add/subtract the leap second when the system had been
up for an even multiple of days, rather than at the end of the d

Fix leap second processing by the kernel time keeping routines.
Before, we would add/subtract the leap second when the system had been
up for an even multiple of days, rather than at the end of the day, as
a leap second is defined (at least wrt ntp). We do this by
calculating the notion of UTC earlier in the loop, and passing that to
get it adjusted. Any adjustments that ntp_update_second makes to this
time are then transferred to boot time. We can't pass it either the
boot time or the uptime because their sum is what determines when a
leap second is needed. This code adds an extra assignment and two
extra compare in the typical case, which is as cheap as I could made
it.

I have confirmed with this code the kernel time does the correct thing
for both positive and negative leap seconds. Since the ntp interface
doesn't allow for +2 or -2, those cases can't be tested (and the folks
in the know here say there will never be a +2s or -2s leap event, but
rather two +1s or -1s leap events).

There will very likely be no leap seconds for a while, given how the
earth is speeding up and slowing down, so there will be plenty of time
for this fix to propigate. UT1-UTC is currently at "about -0.4s" and
decrementing by .1s every 8 months or so. 6 * 8 is 48 months, or 4
years.

-stable has different code, but a similar bug that was introduced
about the time of the last leap second, which is why nobody has
noticed until now.

MFC After: 3 weeks
Reviewed by: phk

"Furthermore, leap seconds must die." -- Cato the Elder

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Use UTC rather than GMT to describe time scale. latter is obsolete.

Use __FBSDID().

Including <sys/stdint.h> is (almost?) universally only to be able to use
%j in printfs, so put a newsted include in <sys/systm.h> where the printf
prototype lives and save everybody else the trouble.

Move timecounters notion of frequency to 64 bits.

[WARNING: CPUs in the distant future may be closer than they appear!]

Add sysctl kern.timecounter.nsetclock which indicates the number of
potential discontinuities in our UTC timescale.

Applications can monitor this variable if they want to be informed
about steps in

Add sysctl kern.timecounter.nsetclock which indicates the number of
potential discontinuities in our UTC timescale.

Applications can monitor this variable if they want to be informed
about steps in the timescale. Slews (ntp and adjtime(2)) and
frequency adjustments (ntp) will not increment this counter, only
operations which set the clock. No attempt is made to classify
size or direction of the step.

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Move a local variable to avoid the compiler warning about it being unused.

hardpps() wants the raw hardware counter value converted to nanoseconds.

Explicitly have the timecounter init happen after the cpu_initclocks is
called. Otherwise (depending on a non-deterministic sort), the timecounter
code can be initialized before the clock rate has b

Explicitly have the timecounter init happen after the cpu_initclocks is
called. Otherwise (depending on a non-deterministic sort), the timecounter
code can be initialized before the clock rate has been set (on ia64) and it
assumes hz = 100, rather than the real value of 1024. I'm not sure how much
gets upset by this.

Glanced at by: phk

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Export tc_tick with sysctl, not tick.

Spotted by: bde

Introduce a "time_uptime" global variable which holds the time since boot
in seconds.

Use strlcpy() instead of strncpy() to copy NUL terminated strings
for safety and consistency.

Do not employ timecounter hardware if our hz does not support their
correct rewinding.

Give up on calling tc_ticktock() from a timeout, we have timeout
functions which run for several milliseconds at a time and getting
in queue behind one or more of those makes us miss our rewind.

Ins

Give up on calling tc_ticktock() from a timeout, we have timeout
functions which run for several milliseconds at a time and getting
in queue behind one or more of those makes us miss our rewind.

Instead call it from hardclock() like we used to do, but retain the
prescaler so we still cope with high HZ values.

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Use a semicolon at the end of a function-like macro invocation. Kills
warnings and makes the visual style easier.

Time counter stats are unsigned, advertise them to sysctl(8) that way.

PR: (one small part of) 19720
Approved by: phk