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

[Doerr, Martin]

Hi Robbin,

awesome. Thank you very much.

Best regards,
Martin


-----Original Message-----
From: Robbin Ehn [mailto:robbin.ehn at oracle.com] 
Sent: Mittwoch, 10. Januar 2018 11:08
To: Doerr, Martin <martin.doerr at sap.com>; Lindenmaier, Goetz <goetz.lindenmaier at sap.com>; hotspot-runtime-dev at openjdk.java.net
Subject: Re: RFR(M): 8194258: PPC64 safepoint mechanism: Fix initialization on AIX and support SIGTRAP

Hi Martin,

I tested it with no problem so I'll push it now.

/Robbin

On 01/02/2018 05:35 PM, Doerr, Martin wrote:
> 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
>>
>>
>