Need help to understand TLS behavior

[cheleswer sahu]

Hi David,
TLS is thread local storage. In test program it is defined using

#define TLS_SIZE 32
int __thread  XYZ[TLS_SIZE * 1024];

Regards,
Cheleswer
On 12/14/2015 6:29 PM, David Holmes wrote:
> What is TLS in this context?
>
> Thanks,
> David
>
> On 14/12/2015 10:34 PM, cheleswer sahu wrote:
>> Hi,
>>
>> I am investigating an issue, in which test with TLS size set to 32K is
>> failing with StackOverFlowError. During investigation I found the below
>> code
>> http://hg.openjdk.java.net/jdk8u/jdk8u/jdk/file/tip/src/solaris/classes/java/lang/UNIXProcess.java 
>>
>>
>>
>>   ThreadFactory threadFactory = grimReaper -> {
>>                  // Our thread stack requirement is quite modest.
>>                  Thread t = new Thread(systemThreadGroup, grimReaper,
>>                                        "process reaper", 32768);
>>
>> Here reaper thread is created with fixed stack size "32768 ", which
>> causes StackOverFlowError  when TLS is set to 32k around.
>> If I remove this fixed size and make it default, test works fine.
>>
>> Thread t = new Thread(systemThreadGroup, grimReaper,
>>                                        "process reaper");
>>
>> I have run several test with TLS size 32k , 64k ,128k and more .
>> The interesting part, it works well with 64k and 128k TLS size but not
>> with 32k.
>> So my questions are as follows:
>>> What is the motivation behind the fixed thread stack size ?
>>> will it be ok to replace the fixed stack size with default or stack
>> size setting is platform sensitive?
>>> How TLS sizes are interpreted internally, which allows 64k and 128k
>> to work but not to 32k ?
>>
>> I would really appreciate, if anyone have any opinion on this.
>>
>> Regards,
>> Cheleswer
>>
>>
>>