RFR: 8234397: add OS uptime information to os::print_os_info output

[Baesken, Matthias]

> 
> The comment in the posix code mentions that it doesn't work on macOS but
> doesn't say anything about Linux. Has it been tested on Solaris?
>

Hi David,  it works on Solaris .
I think I should adjust the comment (saying macOS AND Linux) .

Best regards, Matthias


> >
> > One example that occurred last week  -  my colleague Christoph and me
> were browsing through an hs_err  file of a crash on AIX .
> > When looking into the hs_err  we wanted to know the  uptime because
> our latest  fontconfig - patches   (for getting rid of the crash)    needed a
> reboot too to really work .
> > Unfortunately we  could not find the info , and we were  disappointed  (
> then we noticed the crash is from  OpenJDK and not our internal JVM ).
> >
> >
> >>> Bug/webrev :
> >>> https://bugs.openjdk.java.net/browse/JDK-8234397
> >>> http://cr.openjdk.java.net/~mbaesken/webrevs/8234397.1/
> >>
> >> Can Linux not use the POSIX version?
> >>
> >
> > Unfortunately the posix code does not give the desired result  on Linux (at
> least on my test machines).
> 
> The comment in the posix code mentions that it doesn't work on macOS but
> doesn't say anything about Linux. Has it been tested on Solaris?
> 
> I'm really unsure about this code and am hoping someone more
> knowledgeable in this areas can chime in. I'd be less concerned if there
> was a single POSIX implementation that worked everywhere. :( Though I
> have my general concern about adding yet another potential point of
> failure in the error reporting logic.
> 
> Thanks,
> David
> 
> > Best regards, Matthias
> >