RFR: 8289230: Move PlatformXXX class declarations out of os_xxx.hpp

[David Holmes]

On Tue, 28 Jun 2022 06:16:21 GMT, Ioi Lam <iklam at openjdk.org> wrote:

> There are only two implementations of these classes (one for windows, and one for posix):
> 
> - PlatformEvent
> - PlatformParker
> - PlatformMutex
> - PlatformMonitor
> - ThreadCrashProtection
> 
> Before this PR, these classes are declared in os_xxx.hpp. This causes excessive inclusion of the large header file os.hpp by popular headers such as mutex.hpp, which needs only the declaration of PlatformMutex but not the other stuff in os.hpp
> 
> This PR moves the declarations to park_posix.hpp, mutex_posix.hpp, etc.
> 
> Note:  ideally, the definition of PlatformParker/PlatformEvent should be moved to park_posix.cpp, and PlatformMutex/PlatformMonitor should be moved to mutex_posix.cpp. However, the definition of these 4 classes are intertwined, so I'll leave them inside os_posix.cpp for now. (Same for the Windows version).

Just took a quick skim through to get the general sense of things. Header file split is okay. Pity about the .cpp situation though - maybe move to platform_posix.cpp and platform_windows.cpp to at least get them out of the os_xxx.cpp file?

src/hotspot/os/posix/mutex_posix.hpp line 141:

> 139: };
> 140: 
> 141: #endif // OS_POSIX_PARK_POSIX_HPP

Wrong comment.

src/hotspot/os/posix/threadCrashProtection_posix.cpp line 38:

> 36: 
> 37: /*
> 38:  * See the caveats for this class in os_posix.hpp

Comment needs updating

src/hotspot/os/windows/mutex_windows.hpp line 64:

> 62: };
> 63: 
> 64: #endif // OS_WINDOWS_PARK_WINDOWS_HPP

Wrong comment

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PR: https://git.openjdk.org/jdk/pull/9303