(L) Prelim RFR: 8132510: Replace ThreadLocalStorage with compiler/language-based thread-local variables

[Thomas Stüfe]

Hi David,

builds and works on both variants (with and without USE_LIBRARY_BASED_TLS_ONLY)
on AIX and Linux ppc.

Small nitpicks:

- I probably would have implemented Thread::current() using
Thread::current_or_null().
- Also, instead of using the "raw" ThreadLocalStorage::thread(), I would
have liked a Thread::current_safe() or similar.

Kind Regards, Thomas


On Wed, Nov 11, 2015 at 9:23 PM, David Holmes <david.holmes at oracle.com>
wrote:

> Sorry Thomas the all important:
>
> src/os/posix/vm/threadLocalStorage_posix.cpp
>
> was missing from the webrev. Now adding.
>
> David
> -----
>
> On 12/11/2015 2:47 AM, Thomas Stüfe wrote:
>
>>
>> On Wed, Nov 11, 2015 at 5:36 PM, Thomas Stüfe <thomas.stuefe at gmail.com
>> <mailto:thomas.stuefe at gmail.com>> wrote:
>>
>>     Hi David,
>>
>>     I get build errors on all my platforms.
>>
>>     I think the change misses #include "runtime/threadLocalStorage.hpp"
>>     in a couple of places, at least thread.cpp and possible also the
>>     os_xx_yy.cpp files.
>>
>>
>> Sorry, I have to correct myself. It is a linker error, I do not find the
>> implementations for the ThreadLocalStorage class methods anywhere. I
>> applied your patch atop a freshly synced hs-rt repo:
>>
>> - .../hotspot $ hg log -l 3
>> changeset:   9317:3b23f69bc887 8132510__thread_davids_change qbase qtip
>> tip
>> user:        stuefe
>> date:        Wed Nov 11 16:12:14 2015 +0100
>> summary:     imported patch 8132510__thread_davids_change
>>
>> changeset:   9316:f17e5edbe761 qparent
>> user:        tschatzl
>> date:        Tue Nov 10 11:07:15 2015 +0100
>> summary:     8140689: Skip last young-only gc if nothing to do in the
>> mixed gc phase
>> Reviewed-by: mgerdin, drwhite
>>
>> on AIX I get:
>>
>> ld: 0711-317 ERROR: Undefined symbol: .ThreadLocalStorage::thread()
>> ld: 0711-317 ERROR: Undefined symbol:
>> .ThreadLocalStorage::is_initialized()
>> ld: 0711-317 ERROR: Undefined symbol:
>> .ThreadLocalStorage::set_thread(Thread*)
>> ld: 0711-317 ERROR: Undefined symbol: .ThreadLocalStorage::init()
>>
>> Am I building wrong?
>>
>> Regards, Thomas
>>
>>
>>     Will take another look tomorrow.
>>
>>     Thanks, Thomas
>>
>>     On Wed, Nov 11, 2015 at 9:19 AM, David Holmes
>>     <david.holmes at oracle.com <mailto:david.holmes at oracle.com>> wrote:
>>
>>         Hi Thomas,
>>
>>         Okay here's the next revision:
>>
>>         http://cr.openjdk.java.net/~dholmes/8132510/webrev.v5/
>>
>>         I've reinstated a basic ThreadLocalStorage class which will only
>>         need two implementations: a POSIX one, and a Windows one (still
>>         TBD). This class is always initialized and
>>         ThreadLocalStorage::thread() is used from the signal handlers
>>         (as today).
>>
>>         For platforms that don't have __thread support they can define
>>         USE_LIBRARY_BASED_TLS_ONLY at build time to only use the
>>         ThreadLocalStorage implementation.
>>
>>         Obviously still need to get some performance numbers.
>>
>>         I'd appreciate it if you could retest AIX, though as all
>>         platforms currently use pthread_get/setspecific I'm confident
>>         there will be no platform issues.
>>
>>         Thanks,
>>         David
>>
>>
>>
>>
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