RFR (S) 8130039: Move the platform-specific [OS]Semaphore code

[coleen.phillimore at oracle.com]

On 1/8/18 8:56 PM, David Holmes wrote:
> Hi Coleen,
>
> Overall this seems okay but a few comments ...
>
> On 9/01/2018 8:34 AM, coleen.phillimore at oracle.com wrote:
>> Also:
>> 8130038: Unify the semaphore usage in os_xxx.cpp
>>
>> Tested with hs-tier1-5.  And 
>> open/test/jdk/sun/misc/SunMiscSignalTest.java and closed signal tests.
>>
>> open webrev at http://cr.openjdk.java.net/~coleenp/8130039.01/webrev
>> bug link https://bugs.openjdk.java.net/browse/JDK-8130039
>
> With the removal of os::signal_lookup() the parameter to 
> check_pending_signals becomes irrelevant and the "false" path becomes 
> dead code. Not sure if it is worth deleting that.

Yes, that's true.  I can delete it and the code for the "false" path.
>
> ---
>
> os_linux.cpp:
>
> static struct timespec create_timespec(unsigned int sec, int nsec) {
>   struct timespec ts;
>   // Semaphore's are always associated with CLOCK_REALTIME
>   os::Linux::clock_gettime(CLOCK_REALTIME, &ts);
>   // see unpackTime for discussion on overflow checking
>
> There's no longer a direct connection between create_timespec and the 
> fact it is only used with semaphores - so the initial comment is no 
> longer appropriate. But if you rename to create_semaphore_timespec 
> then that restores the connection.
>

Ok, I'll rename it.

> The final comment is not correct (my bad!) as unpackTime no longer 
> exists since I factored out all the PlatformEvent code. It could say:
>
> // see os_posix.cpp for discussion on overflow checking

I see, it's now similar to calc_rel_time in os_posix.cpp.   I'll change 
the comment as suggested in case calc_rel_time changes we don't have to 
change this.
>
> but I'm wondering whether the timedwait API should be taking a 
> timespec in the first place? If we pass secs and nsecs directly then 
> we only need to convert to a timespec inside the low-level 
> implementation that needs it ie in semaphore_posix.cpp. I don't recall 
> if there was a reason we have to do the timespec conversion in a 
> platform specific manner.
>

I didn't understand the difference between solaris and linux 
create_timespec, so I left it in the platform specific code.  The 
solaris implementation *does* have unpackTime and the linux one does 
not.  Or could I use the linux version in semaphore_posix.cpp ? That 
would be better, but I wasn't sure if it was correct.   Let me know.  
I'd like to make that change.
> ---
>
> semaphore_posix.cpp
>
>   26 #ifndef __APPLE__
>   27 #include "runtime/os.hpp"
>   28 // POSIX unamed semaphores are not supported on OS X.
>   29 #include "semaphore_posix.hpp"
>   30 #include <semaphore.h>
>   31 #endif
>   32
>   33
>   34 // POSIX unamed semaphores are not supported on OS X.
>   35 #ifndef __APPLE__
>
> The whole file contents should be ifndef __APPLE__ so this just 
> reduces to:
>
>   // POSIX unamed semaphores are not supported on OS X.
>   #ifndef __APPLE__
>   #include "runtime/os.hpp"
>   #include "semaphore_posix.hpp"
>   #include <semaphore.h>
>   ...
>

Ok.  I'll fix that.

Thanks,
Coleen
> ---
>
> Thanks,
> David
>
>> Thanks,
>> Coleen