(RFR)(S)(10): 8176768: hotspot ignores PTHREAD_STACK_MIN when creating new threads

[Chris Plummer]

On 3/16/17 11:26 PM, David Holmes wrote:
> On 17/03/2017 2:27 PM, Chris Plummer wrote:
>> Ok, time for a new webrev:
>>
>> http://cr.openjdk.java.net/~cjplummer/8176768/webrev.01/webrev.hotspot
>
> Looks good. Full agreement from me on all the below.
Hi David,

Thanks for your review(s) and all your help and suggestions. Much 
appreciated.

Chris
>
> Thanks,
> David
>
>> The only thing that has changed since the first webrev are the asserts
>> added to os_linux.cpp and os_bsd.cpp. And to summarize what we discuss
>> already:
>>
>>  - The assert should never happen due to the stack size being too small
>> since it will be at least PTHREAD_STACK_MIN.
>>  - The assert should never happen due to an unaligned stack size because
>> we always align it to the page size.
>>  - Any assert would therefore be a VM bug and not due to user error.
>>  - No fixing the java launcher. If the user specifies a stack that is
>> too small, hotspot will already detect this. If the user specifies a
>> stack size that is large enough but not page aligned, then we just
>> ignore any error (if the platform doth protest) and the user gets a main
>> thread with a stack size set to whatever the OS default is.
>>
>> I still need to retest (I only ran TooSmallStackSize.java), but figure
>> getting agreement on the changes first would be best before I bog down
>> our testing resources.
>>
>> thanks,
>>
>> Chris
>>
>> On 3/15/17 10:03 PM, Chris Plummer wrote:
>>> Hello,
>>>
>>> Please review the following:
>>>
>>> https://bugs.openjdk.java.net/browse/JDK-8176768
>>> http://cr.openjdk.java.net/~cjplummer/8176768/webrev.00/webrev.hotspot
>>>
>>> While working on 8175342 I noticed our stack size on xgene was 8mb
>>> even though I was specifying -Xss72k. It turns out the following code
>>> was failing:
>>>
>>>       pthread_attr_setstacksize(&attr, stack_size);
>>>
>>> Although we computed a minimum stack size of 72k, so -Xss72k should be
>>> fine, pthreads on this platform requires the stack be at least 128k,
>>> so it failed the pthread_attr_setstacksize() call. The end result is
>>> pthread_attr_setstacksize() had no impact on the thread's stack size,
>>> and we ended up with the platform default of 8mb. The fix is to round
>>> up the following variables to PTHREAD_STACK_MIN after computing their
>>> new values:
>>>
>>>       _java_thread_min_stack_allowed
>>>       _compiler_thread_min_stack_allowed
>>>       _vm_internal_thread_min_stack_allowed
>>>
>>> For solaris, there was an issue using PTHREAD_STACK_MIN. You need to
>>> #define _POSIX_C_SOURCE >= 199506L in order to get PTHREAD_STACK_MIN
>>> #defined, and this needs to be done before including OS header files.
>>> I noticed that on solaris we were using thr_min_stack() elsewhere
>>> instead of PTHREAD_STACK_MIN, so I decided to do the same with this
>>> fix. Either way is ugly (the #define or using thr_min_stack()).
>>>
>>> And speaking of the existing use of thr_min_stack(), I deleted it. It
>>> was being applied before any adjustments to the stack sizes had been
>>> made (rounding and adding red, yellow, and shadow zones). This mean
>>> the stack ended up being larger than necessary. With the above fix in
>>> place, we are now applying thr_min_stack() after recomputing the
>>> minimum stack sizes. If for any reason one of those stack sizes is now
>>> too small, the correct fix is to adjust the initial stack sizes, not
>>> apply thr_min_stack() to the initial stack sizes. However, it looks
>>> like no adjustment is needed. I did something close to our nightly
>>> testing on all affect platforms, and no new problems turned up.
>>>
>>> thanks,
>>>
>>> Chris
>>
>>