RFR (S): 8228857: Refactor PlatformMonitor into PlatformMutex and PlatformMonitor

[Daniel D. Daugherty]

On 8/1/19 7:03 PM, David Holmes wrote:
> Bug: https://bugs.openjdk.java.net/browse/JDK-8228857
> webrev: http://cr.openjdk.java.net/~dholmes/8228857/webrev/

src/hotspot/os/posix/os_posix.hpp
     L245: // Platform specific implementations that underpin VM 
Monitor/Mutex classes
         Perhaps "Mutex/Monitor" instead of "Monitor/Mutex" now that
         Mutex is the base class. And it will be consistent with the
         new comments that you've added.

src/hotspot/os/posix/os_posix.inline.hpp
     No comments.

src/hotspot/os/posix/os_posix.cpp
     L2277: // Platform Monitor implementation
         Perhaps: // Platform Mutex/Monitor implementation
         like you do in other places.

src/hotspot/os/solaris/os_solaris.hpp
     L338: // Platform specific implementations that underpin VM 
Monitor/Mutex classes
         Perhaps "Mutex/Monitor" instead of "Monitor/Mutex" now that
         Mutex is the base class.

src/hotspot/os/solaris/os_solaris.cpp
     No comments.

src/hotspot/os/windows/os_windows.hpp
     L190: // Platform specific implementations that underpin VM 
Monitor/Mutex classes
         Perhaps "Mutex/Monitor" instead of "Monitor/Mutex" now that
         Mutex is the base class.

src/hotspot/os/windows/os_windows.inline.hpp
     L98: inline os::PlatformMonitor::~PlatformMonitor() {
         I don't remember why there is no 'DeleteConditionVariable()'
         call here. It might be worth a comment to remind the reader.

Thumbs up. If you choose to make the comment tweaks above, I don't
need to see another webrev.

Dan



>
> As suggested by Per Liden when PlatformMonitor was introduced by 
> JDK-8210832 we should refactor PlatformMonitor into a simpler 
> PlatformMutex extended by PlatformMonitor. That would potentially 
> allow other synchronization objects e.g. Zlocks, to be replaced by a 
> suitable PlatformX class, and allows us to redefine JVM_RawMonitor 
> support to use it (forthcoming change).
>
> The refactoring would be obvious and simple if not for the macOS 
> PThread allocation bug workaround. I had to change the Posix variant 
> so that we only use the Impl helper class on macOS, so that we can 
> separate the allocation of the pthread_mutex_t and pthread_cond_t. For 
> macOS both get allocated in the PlatformMutex.
>
> There are not actual usage changes in this RFE.
>
> Testing: mach5 tiers 1-3
>
> Thanks,
> David
> -----
>