RFR(M): 8194258: PPC64 safepoint mechanism: Fix initialization on AIX and support SIGTRAP

[Lindenmaier, Goetz]

Hi Martin, 

thanks for the fixes.  Good that now also aix ist tested. 

Best regards,
  Goetz.

> -----Original Message-----
> From: Doerr, Martin
> Sent: Dienstag, 2. Januar 2018 17:36
> To: Lindenmaier, Goetz <goetz.lindenmaier at sap.com>; hotspot-runtime-
> dev at openjdk.java.net; Robbin Ehn <robbin.ehn at oracle.com>
> Subject: RE: RFR(M): 8194258: PPC64 safepoint mechanism: Fix initialization
> on AIX and support SIGTRAP
> 
> Hi Robbin and Götz,
> 
> thanks for reviewing.
> 
> I have added a comment, improved safepointMechanism_aix.cpp, adapted
> the test OsCpuLoggingTest and added reviewer information.
> 
> New webrev is here:
> http://cr.openjdk.java.net/~mdoerr/8194258_PPC64_poll/webrev.01/
> 
> Please take a look.
> 
> The change applies to jdk10 (as well as to jdk/hs, but it's targeted to 10). Can
> somebody sponsor, please?
> 
> Thanks and best regards,
> Martin
> 
> 
> -----Original Message-----
> From: Lindenmaier, Goetz
> Sent: Samstag, 30. Dezember 2017 14:01
> To: Doerr, Martin <martin.doerr at sap.com>; hotspot-runtime-
> dev at openjdk.java.net; Robbin Ehn <robbin.ehn at oracle.com>
> Subject: RE: RFR(M): 8194258: PPC64 safepoint mechanism: Fix initialization
> on AIX and support SIGTRAP
> 
> Hi Martin,
> 
> thanks for fixing this issue. The change itself looks good.
> 
> Nevertheless some points:
> I would like a comment about the sigtrap mechanism used on
> ppc, maybe where the macro for UseSIGTRAP is set.
> 
> I think you need to adapt runtime/logging/OsCpuLoggingTest.java.
> The tracing is missing on linuxppc, too, if UseSIGTRAP is set.
> Maybe the test should call the VM with -XX:-UseSIGTRAP on ppc?
> And then it should work on aix, too?
> 
> Best regards,
>   Goetz.
> 
> > -----Original Message-----
> > From: Doerr, Martin
> > Sent: Donnerstag, 28. Dezember 2017 18:47
> > To: hotspot-runtime-dev at openjdk.java.net; Robbin Ehn
> > <robbin.ehn at oracle.com>; Lindenmaier, Goetz
> <goetz.lindenmaier at sap.com>
> > Subject: RFR(M): 8194258: PPC64 safepoint mechanism: Fix initialization on
> AIX
> > and support SIGTRAP
> >
> > Hi,
> >
> >
> >
> > unfortunately, the safepoint mechanism initialization on AIX is not
> completely
> > correct, yet. The VM crashes when using -XX:-OptimizePollingPageLocation
> or
> > when allocation at desired addresses failed.
> >
> > Only pages allocated by mmap can be read protected.
> >
> >
> >
> > In addition, SIGTRAP-based polling performs slightly better on PPC64 and
> avoids
> > the need for allocating a protected page.
> >
> >
> >
> > I have uploaded a webrev:
> >
> > http://cr.openjdk.java.net/~mdoerr/8194258_PPC64_poll/webrev.00/
> >
> >
> >
> > We use trap instructions if UseSIGTRAP is enabled (PPC64 specific -XX flag)
> and
> > fall back to loads from the polling pages otherwise.
> >
> >
> >
> > Please review.
> >
> >
> >
> > I will also need a sponsor because I'm changing the shared file
> > safepointMechanism.cpp. It's not a functional change for other platforms.
> >
> >
> >
> > Best regards,
> >
> > Martin
> >
> >