linux/kernel/time/clocksource.c, branch v4.1

clocksource: Improve comment explaining clocks_calc_max_nsecs()'s 50% safety margin

2015-04-03T06:18:35Z

Ingo noted that the description of clocks_calc_max_nsecs()'s 50% safety margin was somewhat circular. So this patch tries to improve the comment to better explain what we mean by the 50% safety margin and why we need it. Signed-off-by: John Stultz Cc: Peter Zijlstra Cc: Prarit Bhargava Cc: Richard Cochran Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1427945681-29972-20-git-send-email-john.stultz@linaro.org Signed-off-by: Ingo Molnar

tick: Move core only declarations and functions to core

2015-04-01T12:22:58Z

No point to expose everything to the world. People just believe such functions can be abused for whatever purposes. Sigh. Signed-off-by: Thomas Gleixner [ Rebased on top of 4.0-rc5 ] Signed-off-by: Rafael J. Wysocki Cc: Nicolas Pitre Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/28017337.VbCUc39Gme@vostro.rjw.lan [ Merged to latest timers/core ] Signed-off-by: Ingo Molnar

tick: Move clocksource related stuff to timekeeping.h

2015-04-01T12:22:58Z

Move clocksource related stuff to timekeeping.h and remove the pointless include from ntp.c Signed-off-by: Thomas Gleixner [ rjw: Subject ] Signed-off-by: Rafael J. Wysocki Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/2714218.nM5AEfAHj0@vostro.rjw.lan Signed-off-by: Ingo Molnar

clocksource: Rename __clocksource_updatefreq_() to __clocksource_update_freq_()

2015-03-13T07:07:08Z

Ingo requested this function be renamed to improve readability, so I've renamed __clocksource_updatefreq_scale() as well as the __clocksource_updatefreq_hz/khz() functions to avoid squishedtogethernames. This touches some of the sh clocksources, which I've not tested. The arch/arm/plat-omap change is just a comment change for consistency. Signed-off-by: John Stultz Cc: Daniel Lezcano Cc: Dave Jones Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Prarit Bhargava Cc: Richard Cochran Cc: Stephen Boyd Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1426133800-29329-13-git-send-email-john.stultz@linaro.org Signed-off-by: Ingo Molnar

clocksource: Add some debug info about clocksources being registered

2015-03-13T07:07:07Z

Print the mask, max_cycles, and max_idle_ns values for clocksources being registered. Signed-off-by: John Stultz Cc: Dave Jones Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Prarit Bhargava Cc: Richard Cochran Cc: Stephen Boyd Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1426133800-29329-12-git-send-email-john.stultz@linaro.org Signed-off-by: Ingo Molnar

clocksource: Mostly kill clocksource_register()

2015-03-13T07:07:06Z

A long running project has been to clean up remaining uses of clocksource_register(), replacing it with the simpler clocksource_register_khz/hz() functions. However, there are a few cases where we need to self-define our mult/shift values, so switch the function to a more obviously internal __clocksource_register() name, and consolidate much of the internal logic so we don't have duplication. Signed-off-by: John Stultz Cc: Dave Jones Cc: David S. Miller Cc: Linus Torvalds Cc: Martin Schwidefsky Cc: Peter Zijlstra Cc: Prarit Bhargava Cc: Richard Cochran Cc: Stephen Boyd Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1426133800-29329-10-git-send-email-john.stultz@linaro.org [ Minor cleanups. ] Signed-off-by: Ingo Molnar

clocksource: Improve clocksource watchdog reporting

2015-03-13T07:07:06Z

The clocksource watchdog reporting has been less helpful then desired, as it just printed the delta between the two clocksources. This prevents any useful analysis of why the skew occurred. Thus this patch tries to improve the output when we mark a clocksource as unstable, printing out the cycle last and now values for both the current clocksource and the watchdog clocksource. This will allow us to see if the result was due to a false positive caused by a problematic watchdog. Signed-off-by: John Stultz Cc: Dave Jones Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Prarit Bhargava Cc: Richard Cochran Cc: Stephen Boyd Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1426133800-29329-9-git-send-email-john.stultz@linaro.org [ Minor cleanups of kernel messages. ] Signed-off-by: Ingo Molnar

clocksource: Add 'max_cycles' to 'struct clocksource'

2015-03-12T09:16:38Z

In order to facilitate clocksource validation, add a 'max_cycles' field to the clocksource structure which will hold the maximum cycle value that can safely be multiplied without potentially causing an overflow. Signed-off-by: John Stultz Cc: Dave Jones Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Prarit Bhargava Cc: Richard Cochran Cc: Stephen Boyd Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1426133800-29329-4-git-send-email-john.stultz@linaro.org Signed-off-by: Ingo Molnar

clocksource: Simplify the logic around clocksource wrapping safety margins

2015-03-12T09:16:38Z

The clocksource logic has a number of places where we try to include a safety margin. Most of these are 12% safety margins, but they are inconsistently applied and sometimes are applied on top of each other. Additionally, in the previous patch, we corrected an issue where we unintentionally in effect created a 50% safety margin, which these 12.5% margins where then added to. So to simplify the logic here, this patch removes the various 12.5% margins, and consolidates adding the margin in one place: clocks_calc_max_nsecs(). Additionally, Linus prefers a 50% safety margin, as it allows bad clock values to be more easily caught. This should really have no net effect, due to the corrected issue earlier which caused greater then 50% margins to be used w/o issue. Signed-off-by: John Stultz Acked-by: Stephen Boyd (for the sched_clock.c bit) Cc: Dave Jones Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Prarit Bhargava Cc: Richard Cochran Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1426133800-29329-3-git-send-email-john.stultz@linaro.org Signed-off-by: Ingo Molnar

clocksource: Simplify the clocks_calc_max_nsecs() logic

2015-03-12T09:16:38Z

The previous clocks_calc_max_nsecs() code had some unecessarily complex bit logic to find the max interval that could cause multiplication overflows. Since this is not in the hot path, just do the divide to make it easier to read. The previous implementation also had a subtle issue that it avoided overflows with signed 64-bit values, where as the intervals are always unsigned. This resulted in overly conservative intervals, which other safety margins were then added to, reducing the intended interval length. Signed-off-by: John Stultz Cc: Dave Jones Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Prarit Bhargava Cc: Richard Cochran Cc: Stephen Boyd Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1426133800-29329-2-git-send-email-john.stultz@linaro.org Signed-off-by: Ingo Molnar

linux/kernel/time/clocksource.c, branch v4.1

clocksource: Improve comment explaining clocks_calc_max_nsecs()'s 50% safety margin

tick: Move core only declarations and functions to core

tick: Move clocksource related stuff to timekeeping.h

clocksource: Rename __clocksource_updatefreq_*() to __clocksource_update_freq_*()

clocksource: Add some debug info about clocksources being registered

clocksource: Mostly kill clocksource_register()

clocksource: Improve clocksource watchdog reporting

clocksource: Add 'max_cycles' to 'struct clocksource'

clocksource: Simplify the logic around clocksource wrapping safety margins

clocksource: Simplify the clocks_calc_max_nsecs() logic

clocksource: Rename __clocksource_updatefreq_() to __clocksource_update_freq_()