RFR(S): 8200450: Analysis and fix for JDK-8200366 (SIGSEGV in print_names())

[Vladimir Kozlov]

I got build failure on Windows:

src/hotspot/share/code/codeHeapState.cpp(2098) : warning C4267: 'initializing' : conversion from 
'size_t' to 'unsigned int', possible loss of data

Testing on other platforms seems fine.

Thanks,
Vladimir

On 4/17/18 2:15 PM, Vladimir Kozlov wrote:
> Thank you, Lutz
> 
> I agree with this approach with additional safeguarding checks. It has less affects on other code.
> 
> I start testing of these changes.
> 
> Thanks,
> Vladimir
> 
> On 4/17/18 8:49 AM, Schmidt, Lutz wrote:
>> Dear all,
>>
>> may I please request your comments on this topic.
>>
>> I have invested quite some time in testing, reproducing, analyzing, and fixing the effects that 
>> caused the CodeHeap State Analytics function print_names() to SIGSEGV (very rare, intermittent). 
>> Please refer to my description in the bug for the details (I did not want to duplicate it here).
>>
>> I have prepared an preliminary webrev as a basis for further discussions. The webrev is 
>> preliminary at least with respect to the debugging/tracing output which is still in there 
>> intentionally. I thought it might be helpful for you to see how I tested that the changes actually 
>> hardened the code. A potential push candidate would have all #ifdef JDK8200450_TRACE sections 
>> removed. All #ifndef JDK8200450_REMEDY sections would be gone as well.
>>
>> As workload I ran SPECjvm2008. From a separate process, I hammered sets of
>>   - ${jcmd} ${testPID} Compiler.CodeHeap_Analytics discard
>>   - ${jcmd} ${testPID} Compiler.CodeHeap_Analytics aggregate
>>   - ${jcmd} ${testPID} Compiler.CodeHeap_Analytics MethodNames (50 repetitions)
>>   - start over
>> against the JVM. The pace was only limited by system capabilities. I scanned the output for marker 
>> strings to find handled issues which previously would have caused a SIGSEGV. Platforms tested are 
>> bsd_x86, linux_x86, linux_ppc, linux_s390. A handled issue was reported less frequently than 1 in 
>> 10,000. Unhandled issued were not encountered at all.
>>
>> In addition, I cleaned the format strings a bit, replacing "%p" by INTPTR_FORMAT.
>>
>> Bug:    https://bugs.openjdk.java.net/browse/JDK-8200450
>> Webrev: http://cr.openjdk.java.net/~lucy/webrevs/8200450.00/
>>
>> Thanks for having a look!
>> Lutz
>>