RFR 8009302: JVM crash on infinite recursion on Appkit Thread

Coleen Phillimore coleen.phillimore at oracle.com
Tue Jun 4 14:27:55 PDT 2013

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.


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

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