RFR: Fix jtreg test runtime/StackGuardPages/

[Siebenborn, Axel]

Hi Mikael,
Both  tests fails because 
res = (*_jvm)->AttachCurrentThread(_jvm, (void **)&env, NULL);
returns with an error (res != JNI_OK).

AttachCurrentThread uses the current thread as JavaThread and allocates a java level Thread object and needs to run initializing java code (JavaThread::allocate_threadObj).
In order to run java code, the remaining stack space is checked. There must be sufficient  space for an interpreter frame, the java frame and shadow pages ( JavaCalls::call_helper() ). The default for the number of shadow pages is 10 for a release build. If this check fails a StackOverflowException is thrown.
As we return with a pending exception the attach fails and we return JNI_ERR.

This is a problem as we call AttachCurrentThread from a thread that we created with the default stacksize. Threads created by the jvm are created with a much higher stacksize.

webrev_a fixes the test by providing an argument for the stacksize to pthread_create.

webrev_b reduces the amount of shadow pages.

Does that make things clearer?

Regards,
Axel


> -----Original Message-----
> From: Mikael Vidstedt [mailto:mikael.vidstedt at oracle.com]
> Sent: Dienstag, 3. April 2018 00:01
> To: Siebenborn, Axel <axel.siebenborn at sap.com>
> Cc: portola-dev at openjdk.java.net
> Subject: Re: RFR: Fix jtreg test runtime/StackGuardPages/
> 
> 
> Alex,
> 
> Can you please add some additional color/details to why it fails? Is it the
> native or java variant that fails (or both)?
> 
> I understand that the stack is smaller with musl (I ran into that problem in a
> different context), but I’m not sure I see why Thread.init() would fail just
> because of that. Help? :)
> 
> Cheers,
> Mikael
> 
> > On Mar 22, 2018, at 3:37 AM, Siebenborn, Axel
> <axel.siebenborn at sap.com> wrote:
> >
> > Hi,
> >
> > the test  runtime/StackGuardPages/ fails, as AttachCurrentThread() returns
> with an error. The reason is a stackoverflow while trying to run java
> Thread.init().
> > The default pthread stack size is 80 K, much less than on other Unixes.
> >
> > The first fix is to check the pthread default stacksize and increase it if it's
> less than 160K.
> >
> > Webrev a:
> >
> http://cr.openjdk.java.net/~asiebenborn/jtreg_StackGuardPages/webrev_a
> /
> >
> > However, the reason we need that much stack, just to run a single java
> method, is the large amount of shadow pages.
> > The second fix is just to add a flag to JNI_CreateJavaVM, to set the number
> of shadow pages to a lower value. However, a change in globals_x86.hpp is
> needed to allow smaller minimum for that value. Here I miss a macro like
> MUSL_OLNLY(code).
> >
> > Webrev b:
> >
> http://cr.openjdk.java.net/~asiebenborn/jtreg_StackGuardPages/webrev_
> b/
> >
> > I'm unsure which change to use.
> > What do you think?
> >
> > Regards,
> > Axel
> >
> >