RFR 8009302: JVM crash on infinite recursion on Appkit Thread

[Gerard Ziemski]

Thank you for the review and being so supportive and patient.


cheers

On 6/4/2013 4:27 PM, Coleen Phillimore wrote:
>
> Hi Gerard,
>
> This looks good.  Thank you for doing the detailed analysis of this 
> issue, which included debugging the bsd kernel.   The comment is good 
> also.
>
> Thanks,
> Coleen
>
> On 06/04/2013 02:34 PM, Gerard Ziemski wrote:
>> hi guys,
>>
>> Here is a trivial fix (workaround) for a particular XNU (Mac OS X 
>> kernel) behavior causing JavaVM problems.
>>
>> Explanation:
>>
>> There is a case where XNU will map SIGBUS into SIGSEGV, which only 
>> happens on main thread (secondary threads receive the original 
>> SIGBUS) due to the way XNU determines stack address and its size. To 
>> complicate the issue, XNU will only deliver that converted SIGSEGV 
>> signal if the BSD signal catcher uses an alternate stack.
>>
>> Since JavaVM BSD signal catcher does not use alt stack, we end up 
>> missing the signal and the Java process results in a native crash 
>> which is then presented to the user via Mac CrashReporter app.
>>
>> We do not want to use an actual alternate stack, which among other 
>> things would result in an increased RAM usage and possibly result in 
>> a regression, so we use a workaround, where we declare we will use an 
>> alternate stack, without actually creating one.
>>
>> This workaround is only for Mac (ie. we use #ifdef __APPLE__) and it 
>> works because we install our own guard pages, and that's where the 
>> faulting address occurs, so we are assured that our stack does have 
>> enough room to handle the signal by the existing JavaVM code, which 
>> removes the guard pages before handling the signal.
>>
>> I have filed an issue with Apple (id: 14047928) to fix this 
>> inconsistent (wrt threads) behavior in XNU, and wrote native tests 
>> that check for this particular behavior, which will catch any future 
>> change, should Apple ever elect to fix it.
>>
>>
>> Testing:
>>
>> - the issue's own use case
>> - vm.quick.testlist
>> - vm.signal.testlist
>> - nsk.stack.testlist
>> - JPRT
>> - JCK lang
>> - JCK vm
>>
>>
>> References:
>>
>> Webrev: http://cr.openjdk.java.net/~hseigel/bug_8009302/
>>
>> OpenJDK bug  http://bugs.sun.com/view_bug.do?bug_id=8009302
>>
>> JBS bug: https://jbs.oracle.com/bugs/browse/JDK-8009302
>>
>
>
>