RFR(M): 8194258: PPC64 safepoint mechanism: Fix initialization on AIX and support SIGTRAP
martin.doerr at sap.com
Thu Dec 28 17:47:03 UTC 2017
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:
We use trap instructions if UseSIGTRAP is enabled (PPC64 specific -XX flag) and fall back to loads from the polling pages otherwise.
I will also need a sponsor because I'm changing the shared file safepointMechanism.cpp. It's not a functional change for other platforms.
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