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* sys/sys: further adoption of SPDX licensing ID tags.Pedro F. Giffuni2017-11-271-0/+2
| | | | | | | | | | | | | | | Mainly focus on files that use BSD 2-Clause license, however the tool I was using misidentified many licenses so this was mostly a manual - error prone - task. The Software Package Data Exchange (SPDX) group provides a specification to make it easier for automated tools to detect and summarize well known opensource licenses. We are gradually adopting the specification, noting that the tags are considered only advisory and do not, in any way, superceed or replace the license texts. Notes: svn path=/head/; revision=326256
* Core structure and functions to support a feed-forward clock within the kernel.Lawrence Stewart2011-11-191-0/+42
Implement ffcounter, a monotonically increasing cumulative counter on top of the active timecounter. Provide low-level functions to read the ffcounter and convert it to absolute time or a time interval in seconds using the current ffclock estimates, which track the drift of the oscillator. Add a ring of fftimehands to track passing of time on each kernel tick and pick up updates of ffclock estimates. Committed on behalf of Julien Ridoux and Darryl Veitch from the University of Melbourne, Australia, as part of the FreeBSD Foundation funded "Feed-Forward Clock Synchronization Algorithms" project. For more information, see http://www.synclab.org/radclock/ Submitted by: Julien Ridoux (jridoux at unimelb edu au) Notes: svn path=/head/; revision=227723