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

[David Holmes]

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?

> 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_ ?


BTW I like the idea of using the semaphore, we're just haggling on the 
details. ;-)

Thanks,
David

> /R
>
>> ??
>>
>> David
>> -----
>