[RTEMS Project] #3175: Merge FreeBSD timecounter changes from 2015-01-20 to now

[RTEMS trac]

#3175: Merge FreeBSD timecounter changes from 2015-01-20 to now
-----------------------------+------------------------------
 Reporter:  Sebastian Huber  |       Owner:  Sebastian Huber
     Type:  enhancement      |      Status:  assigned
 Priority:  normal           |   Milestone:  4.12.0
Component:  score            |     Version:  4.12
 Severity:  normal           |  Resolution:
 Keywords:                   |
-----------------------------+------------------------------

Comment (by Konstantin Belousov <kib@…>):

 In [changeset:"f013c1476e3c1184aa18d7e33fd219e253db192f/rtems"
 f013c14/rtems]:
 {{{
 #!CommitTicketReference repository="rtems"
 revision="f013c1476e3c1184aa18d7e33fd219e253db192f"
 timecounter: Merge FreeBSD change r288216

 Use per-cpu values for base and last in tc_cpu_ticks(). The values are
 updated lockess, different CPUs write its own view of timecounter state.
 The critical section is done for safety, callers of tc_cpu_ticks() are
 supposed to already enter critical section, or to own a spinlock.

 The change fixes sporadical reports of too high values reported for
 the (W)CPU on platforms that do not provide cpu ticker and use
 tc_cpu_ticks(), in particular, arm*.

 Diagnosed and reviewed by:      jhb
 Sponsored by:   The FreeBSD Foundation
 MFC after:      1 week

 Update #3175.
 }}}

--
Ticket URL: <http://devel.rtems.org/ticket/3175#comment:10>
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