RFR: 8279887: 2 Null pointer dereference defect groups in os_posix.cpp

[Coleen Phillimore]

On Tue, 18 Jan 2022 15:00:50 GMT, Harold Seigel <hseigel at openjdk.org> wrote:

> Please review this small fix to prevent possible Null pointer dereferences.  The fix adds a Null check to prevent trying to park a Null thread.  The Null check is needed because UNSAFE_ENTRY calls thread_from_jni_environment(), which returns NULL if the env thread is terminated. 
> 
> The fix was tested with Mach5 tiers 1-2 on Linux, Mac OS, and Windows, and Mach5 tiers 3-5 on Linux x64.
> 
> Thanks, Harold

Looks good to me. Seems like returning NULL for an impossible case is ok, since that's what UnPark does.

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Marked as reviewed by coleenp (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/7129