(10) (M) RFR: 8174231: Factor out and share PlatformEvent and Parker code for POSIX systems

[David Holmes]

Bug: https://bugs.openjdk.java.net/browse/JDK-8174231

webrevs:

Build-related: http://cr.openjdk.java.net/~dholmes/8174231/webrev.top/
       hotspot: http://cr.openjdk.java.net/~dholmes/8174231/webrev.hotspot/

First a big thank you to Thomas Stuefe for testing various versions of 
this on AIX.

This is primarily a refactoring and cleanup exercise (ie lots of deleted 
duplicated code!).

I have taken the PlatformEvent, PlatformParker and Parker::* code, out 
of os_linux and moved it into os_posix for use by Linux, OSX, BSD, AIX 
and perhaps one day Solaris (more on that later).

The Linux code was the most functionally complete, dealing with correct 
use of CLOCK_MONOTONIC for relative timed waits, and the default 
wall-clock for absolute timed waits. That functionality is not, 
unfortunately, supported by all our POSIX platforms so there are some 
configure time build checks to set some #defines, and then some dynamic 
lookup at runtime**. We allow for the runtime environment to be less 
capable than the build environment, but not the other way around 
(without build time support we don't know the runtime types needed to 
make library calls).

** There is some duplication of dynamic lookup code on Linux but this 
can be cleaned up in future work if we refactor the time/clock code into 
os_posix as well.

The cleanup covers a number of things:
- removal of linux anachronisms that got "ported" into the other platforms
   - eg EINTR can not be returned from the wait methods
- removal of solaris anachronisms that got ported into the linux code 
and then on to other platforms
   - eg ETIMEDOUT is what we expect never ETIME
- removal of the ancient/obsolete os::*::allowdebug_blocked_signals() 
from the Parker methods
- consolidation of unpackTime and compute_abstime into one utility function
- use statics for things completely private to the implementation rather 
than making them part of the os* API (eg access to condAttr objects)
- cleanup up commentary and style within methods of the same class
- clean up coding style in places eg not using Names that start with 
capitals.

I have not tried to cleanup every single oddity, nor tried to reconcile 
differences between the very similar in places PlatformEvent and Park 
methods. For example PlatformEvent still examines the 
FilterSpuriousWakeups** flag, and Parker still ignores it.

** Perhaps a candidate for deprecation and future removal.

There is one mini "enhancement" slipped in this. I now explicitly 
initialize mutexes with a mutexAttr object with its type set to 
PTHREAD_MUTEX_NORMAL, instead of relying on the definition of 
PTHREAD_MUTEX_DEFAULT. On FreesBSD the default is not "normal" but 
"error checking" and so is slow. On all other current platforms there is 
no effective change.

Finally, Solaris is excluded from all this (other than the debug signal 
blocking cleanup) because it potentially supports three different 
low-level sync subsystems: UI thr*, Pthread, and direct LWP sync. 
Solaris cleanup would be a separate RFE.

No doubt I've overlooked mentioning something that someone will spot. :)

Thanks,
David