RFR(s): 8235410: Enable handshakes on Linux x86 (32-bit)

[Robbin Ehn]

Thanks Dan!

/Robbin

On 2019-12-11 15:13, Daniel D. Daugherty wrote:
> Thumbs up.
> 
> One left after this:
> 
>  > src/hotspot/cpu/arm/globals_arm.hpp:define_pd_global(bool, 
> ThreadLocalHandshakes, false);
> 
> but that one should be take care of with the fix for:
> 
> 8229971 Arm32: implementation for Thread-local handshakes
> 
> that Boris sent out for review...
> 
> Almost there...
> 
> Dan
> 
> 
> On 12/5/19 9:01 AM, Robbin Ehn wrote:
>> Hi all, please review.
>>
>> The flag ThreadLocalHandshakes is going to be obsolete in JDK 14.
>> So we change the (unchangeable) default for Linux x86 to on/true.
>>
>> There is a follow-up which removes ThreadLocalHandshakes completely.
>> If the platform defines THREAD_LOCAL_POLL it will use handshakes.
>> When arm32 have implemented local polls, the plan is to remove the 
>> global poll
>> code paths.
>>
>> Last time I checked with some of the affected parties there was no 
>> objections.
>>
>> Built and sanity test.
>>
>> Issue:
>> https://bugs.openjdk.java.net/browse/JDK-8235410
>>
>> Code below.
>>
>> Thanks, Robbin
>>
>> diff -r 636d71e53732 src/hotspot/cpu/x86/globals_x86.hpp
>> --- a/src/hotspot/cpu/x86/globals_x86.hpp    Wed Dec 04 10:26:32 2019 
>> +0100
>> +++ b/src/hotspot/cpu/x86/globals_x86.hpp    Thu Dec 05 14:13:57 2019 
>> +0100
>> @@ -89,12 +89,7 @@
>>
>>  define_pd_global(intx, InitArrayShortSize, 8*BytesPerLong);
>>
>> -#if defined(_LP64) || defined(_WINDOWS)
>>  define_pd_global(bool, ThreadLocalHandshakes, true);
>> -#else
>> -// get_thread() is slow on linux 32 bit, therefore off by default
>> -define_pd_global(bool, ThreadLocalHandshakes, false);
>> -#endif
>>
>>  #define ARCH_FLAGS(develop, \
>>                     product, \
>>
>