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

[Rickard Bäckman]

David,

this is what the suggested semaphore.cpp/semaphore.hpp. Is that what you are looking for?

Webrev: http://cr.openjdk.java.net/~rbackman/webrev/

Thanks
/R

On Apr 15, 2013, at 8:59 AM, David Holmes wrote:

> 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
>>>>>> -----
>>>>> 
>>> 
>>