RFR: 8011882: Replace spin loops as back off when suspending

David Holmes david.holmes at oracle.com
Sun Apr 14 23:59:39 PDT 2013


On 15/04/2013 4:55 PM, Rickard Bäckman wrote:
> David,
>
> any new thoughts?

Not a new one but I think factoring into Semaphore.hpp/cpp and using a 
few ifdefs is better than three versions of the Semaphore class. The 
signal thread could use it also.

David

> Thanks
> /R
>
> On Apr 12, 2013, at 8:06 AM, Rickard Bäckman wrote:
>
>>
>> On Apr 12, 2013, at 7:34 AM, David Holmes wrote:
>>
>>> On 12/04/2013 3:01 PM, Rickard Bäckman wrote:
>>>>
>>>> On Apr 12, 2013, at 1:04 AM, David Holmes wrote:
>>>>
>>>>> On 11/04/2013 11:02 PM, Rickard Bäckman wrote:
>>>>>> On Apr 11, 2013, at 2:39 PM, David Holmes wrote:
>>>>>>> So what did you mean about pthread_semaphore (what is that anyway?) ??
>>>>>>
>>>>>> Never mind, pthread condition variables.
>>>>>
>>>>> Ah I see.
>>>>>
>>>>>>>
>>>>>>> I really, really, really don't like seeing three versions of this class :( Can't BSD and Linux at least share a POSIX version? (And I wonder if we can actually mix-n-match UI threads on Solaris with POSIX semaphores on Solaris?)
>>>>>>
>>>>>> I don't like it either, our OS code isn't really helpful when it comes do reusing things :) Not sure how I would layout things to make them only available on BSD (Not Mac) and Linux. I guess os_posix.hpp with lots of #ifdefs, but I'm not sure I"m feeling that happy about that.
>>>>>
>>>>> Why would the os_posix version need a lot of ifdefs?
>>>>
>>>> Well, I guess we would need:
>>>>
>>>> (in ifdef pseudo language)
>>>>
>>>> #ifdef (LINUX || (BSD && !APPLE))
>>>>>>>> #endif
>>>
>>> But if it isn't "posix" then we won't be building os_posix - right?
>>
>> Linux, Solaris, Bsd & Mac builds and include os_posix. They are all "implementing posix" we are just not using the same semaphore implementation on all of them.
>>
>>>
>>>> The second interesting problem this will get us into is that sem_t is not declared in this context. Where do we put the #include <semaphore.h>? Impossible in os_posix.hpp since it is included in the middle of a class definition. I could put it in os.hpp in the #ifdef path that does the jvm_platform.h includes, not sure if that is very pretty either.
>>>
>>> Semaphores are already used by the signal handler thread - semaphore.h is included in os_linux.cpp etc, so why would os_posix be any different ?
>>>
>>> But couldn't we just have a Semaphore.h/cpp with any needed ifdefs?
>>>
>>>>> Do we really have four versions:
>>>>> - linux (posix)
>>>>> - BSD (posix)
>>>>> - Solaris
>>>>> - Mac (different to BSD?)
>>>>>
>>>>
>>>> 3:
>>>> 1) linux & bsd uses the sem_ interface
>>>> 2) solaris uses the sema_ interface
>>>> 3) mac uses the semaphore_ interface
>>>
>>> Okay but if mac is BSD why can't we use bsd ie posix interface instead of the mach semaphore_ ?
>>
>> Because apple decided not to implement sem_timedwait.
>> On Solaris we use sema_ because sem_ requires us to link with -lrt which we currently don't (and I'm not really feeling like adding it)
>>
>>>
>>>
>>> BTW I like the idea of using the semaphore, we're just haggling on the details. ;-)
>>
>> I'm fine with that :)
>>
>> /R
>>
>>>
>>> Thanks,
>>> David
>>>
>>>> /R
>>>>
>>>>> ??
>>>>>
>>>>> David
>>>>> -----
>>>>
>>
>


More information about the hotspot-runtime-dev mailing list