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

Robbin Ehn robbin.ehn at oracle.com
Fri Dec 29 11:50:00 UTC 2017


Hi Martin,

Looks fine!

/Robbin

On 2017-12-28 18:47, Doerr, Martin wrote:
> 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
> 


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