[OpenJDK 2D-Dev] Question regarding the integration of harfbuzz (JEP 258)

[Behdad Esfahbod]

Hi Volker, Steven,

I'd happily take AIX atomic primitive patch for HarfBuzz.  Yes, github
Pull-Requests are fine.  As you correctly identified, HarfBuzz uses atomic
ops and mutexes to synchronize access to global data as well as
reference-counting from multiple threads, even though it doesn't uses
threads itself.

Does AIX use pthread for threading?  I can definitely add a threading
stress-test to HarfBuzz.  I definitely should.  Filed here:

  https://github.com/behdad/harfbuzz/issues/195

Thanks,
behdad

On Thu, Dec 10, 2015 at 2:27 PM, Volker Simonis <volker.simonis at gmail.com>
wrote:

> Hi Steven,
>
> thanks for your response.
>
> On Thu, Dec 10, 2015 at 1:44 AM, Steven R. Loomis <srl at icu-project.org>
> wrote:
>
>> Volker,
>>  0. I’d like to see what the crashing stack frame is when NOT on
>> harfbuzz, because there should be no change.
>>
>>
> This was another problem. Please see my previous mail in this thread where
> I've described the cause in more detail.
>
>
>>  1. Phil addressed this one
>>
>>  2. I will take a look on AIX. I’ll see if I can build Harfbuzz itself on
>> AIX at first.
>>
>>
> I've fixed it now and just send around a request for review:
> http://mail.openjdk.java.net/pipermail/2d-dev/2015-December/006065.html
>
> The mail contains a link to the bug and the patch which fixes it.
>
> I also want to contribute this to harfbuzz. Is it OK to send a pull
> request to https://github.com/behdad/harfbuzz ?
>
>  3. Yes, I’ll work on putting some docs together for that test.  Actually,
>> other tests such as the Font2DTest  would be a good test. Or, any text in a
>> complex script such as Hindi.
>>
>>
> That would be great. For now, the Font2DTest runs without a problem with
> harfbuzz on AIX (and linux/ppc64).
>
>
>>  4. I’m not sure. A threaded stress test would be good.  Perhaps
>> Harfbuzz-in-JDK could leverage the
>> hotspot/src/os_cpu/../vm/atomic_os_cp.inline.hpp you mentioned.
>>
>>  Behdad - file is here
>> http://hg.openjdk.java.net/jdk9/client/hotspot/file/c8e212fb27d0/src/os_cpu/linux_x86/vm/atomic_linux_x86.inline.hpp
>>  - any comments on this or other items?
>>
>>
> That sounds like a good idea but unfortunately the hotspot primitives are
> in a different repository (source-code wise) and in a different library
> (i.e. libjvm.so) which doesn't export them. So the best we can do for now
> would be to copy the missing parts over to the jdk repository (and that's
> actually what I've done now for the AIX version of the primitives).
>
> Regards,
> Volker
>
>
>> -s
>>
>>
>> -------- Original Message -------- Subject: Re: [OpenJDK 2D-Dev]
>> Question regarding the integration of harfbuzz (JEP 258) Date: Wed, 09
>> Dec 2015 09:02:33 -0800 From: Philip Race <philip.race at oracle.com>
>> <philip.race at oracle.com> Organization: Oracle Corporation To:
>> 2d-dev at openjdk.java.net
>>
>>
>> Hi Volker,
>>
>> Running with ICU should stop harfbuzz use completely so if
>> you are still seeing a crash, perhaps it is due to something else entirely.
>> Especially since a "simple AWT program" should not load layout anyway.
>> There was a fair amount of new and changed code pushed recently ...
>>
>> Yes, we need to run harfbuzz in multiple concurrent threads in the JDK.
>> A single threaded lock on harfbuzz would throttle text operations.
>> I suppose it is possible that we do not strictly need it as we currently
>> create a
>> new harfbuzz "instance" each time we go to invoke layout but that
>> is something that at least theoretically could change.
>>
>> The approach to synchronization is all from up-stream harfbuzz.
>> The harfbuzz mailing list might be the place to discuss that.
>> I'd expect it does work on AIX as a principal driver here is that
>> the IBM sponsored ICU project has deprecated its layout engine
>> and IBM/ICU are moving to harfbuzz so I'd be somewhat astonished
>> if they haven't yet tried it on AIX. Did you try just getting a copy
>> of the full hotspot library and running its configure on AIX to see if
>> harfbuzz can work out which options it wants there ? Obviously
>> I did not try that since I don't have AIX. Steven Loomis of IBM
>> who submitted the JEP should be able to help with a lot of this.
>>
>> -phil.
>>
>> On 12/8/15, 10:50 AM, Volker Simonis wrote:
>> > Hi,
>> >
>> > the integration of harfbuzz broke our AIX build because there's no
>> > implementation available for the hb_atomic macros in
>> > hb-atomic-private.hh. I've fixed that locally but still get a crash
>> > when running a simple AWT program (even with
>> > -Dsun.font.layoutengine=icu).
>> >
>> > I'm curretnly debugging the problem, but I have some general questions:
>> >
>> > 1. Do we really need the multi-threaded features of harfbuzz in OpenJDK?
>> >
>> > 2. Why does hurbuzz require these synchronization macros? From a first
>> > glance it doesn't seem to use multiple threads by itself. Does it have
>> > some global data structures which it needs to protect if harfbuzz is
>> > called from various threads?
>> >
>> > 3. Is there a way to test the hurfbuzz engine on a new platform? I saw
>> > the new test TestLayoutVsICU.java but it is marked as "manual" and it
>> > seems to require external fonts (at least some of which seem to be
>> > freely available). Could you please provide at least a minimal
>> > description on how this test can be run?
>> >
>> > 4. Is there a way to test that the implementation of the hb_atomic
>> > macros in hb-atomic-private.hh is correct (i.e. a way to stress
>> > harfbuzz from multiple threads)? I think this is important as I
>> > couldn't find a good description of the requirements for the atomic
>> > macros and on weak memory model architectures we should really get
>> > this right. For example there's no description of which fences are
>> > required around the various atomic operations. Getting this right
>> > across all platforms in the HotSpot (see
>> > hotspot/src/os_cpu/../vm/atomic_os_cp.inline.hpp) is already hard
>> > enough so I'm a little concerned that we are now introducing similar
>> > primitives in the class library.
>> >
>> > Thank you and best regards,
>> > Volker
>>
>>
>>
>
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