RFR(XS)(10): 8175342: assert(InstanceKlass::cast(k)->is_initialized()) failed: need to increase java_thread_min_stack_allowed calculation

[Chris Plummer]

Thanks!

On 3/17/17 1:14 AM, Dmitry Samersoff wrote:
> Chris,
>
> Looks good to me.
>
> -Dmitry
>
> On 2017-03-17 10:31, Chris Plummer wrote:
>> I should have been more clear. I need one more "reviewer", not another
>> review from David.
>>
>> thanks,
>>
>> Chris
>>
>> On 3/17/17 12:30 AM, Chris Plummer wrote:
>>> Thanks for the review, David.
>>>
>>> I could still use one more review. Here's an updated webrev.
>>>
>>> http://cr.openjdk.java.net/~cjplummer/8175342/webrev.01/webrev.jdk
>>>
>>> cheers,
>>>
>>> Chris
>>>
>>> On 3/15/17 10:14 PM, David Holmes wrote:
>>>> Hi Chris,
>>>>
>>>> On 16/03/2017 2:57 PM, Chris Plummer wrote:
>>>>> Hello,
>>>>>
>>>>> Please review the following:
>>>>>
>>>>> https://bugs.openjdk.java.net/browse/JDK-8175342
>>>>> http://cr.openjdk.java.net/~cjplummer/8175342/webrev.00/webrev.jdk
>>>> I think you want to disable the guardpage always, not just when a
>>>> specific stack size is requested. You might not miss 64KB in 8MB but
>>>> logically the guard page is never needed.
>>>>
>>>> Thanks,
>>>> David
>>>> -----
>>>>
>>>>> The assert is somewhat misleading, although it did properly detect a
>>>>> "too small" stack issue. The test was run with -Xss256k on a system
>>>>> with
>>>>> 64k pages. On this system 256k is suppose to be the smallest allowed
>>>>> stack size, so -Xss256k should work. The thread that the assert happens
>>>>> on is the main thread created by ContinueInNewThread0(). By default
>>>>> pthread gives new threads a guard page the size of an OS page. pthreads
>>>>> is suppose to add additional stack space for the guard page, but it
>>>>> doesn't. Later we call current_stack_region(), which among other
>>>>> things,
>>>>> computes the size of the stack. It has the following code to deal with
>>>>> the pthread guard page bug:
>>>>>
>>>>>      // Work around NPTL stack guard error.
>>>>>      size_t guard_size = 0;
>>>>>      rslt = pthread_attr_getguardsize(&attr, &guard_size);
>>>>>      *bottom += guard_size;
>>>>>      *size   -= guard_size;
>>>>>
>>>>> So the net effect is hotspot treats the stack as only being 192k, not
>>>>> 256k. However, in terms of usable stack space, hotspot then also
>>>>> subtracts the red, yellow, and shadow zones. Each of these is one OS
>>>>> page. So that subtracts another 192k, leaving us with 0k. The assert is
>>>>> a by product of this.
>>>>>
>>>>> It turns out this pthread guard page problem is already fixed for all
>>>>> java threads except the main thread. We do the following in
>>>>> os::create_thread():
>>>>>
>>>>>    pthread_attr_setguardsize(&attr,
>>>>> os::Linux::default_guard_size(thr_type));
>>>>>
>>>>> For java threads, os::Linux::default_guard_size() returns 0, so the
>>>>> above code removes the guard page for java threads. The fix I'm
>>>>> proposing for the main thread does the same.
>>>>>
>>>>> Tested by running the test in question dozens of times on all supported
>>>>> platforms. Also ran most tests we do for nightlies except for longer
>>>>> running ones.
>>>>>
>>>>> thanks,
>>>>>
>>>>> Chris
>>>
>