RFR: 8252543: [JVMCI] Libgraal can deadlock in blocking compilation mode

[Vladimir Kozlov]

On Sun, 6 Sep 2020 19:48:08 GMT, Doug Simon <dnsimon at openjdk.org> wrote:

> To prevent a deadlock in libgraal under `-Xcomp` or `-Xbatch` due to a lock being held in libgraal, a new mechanism is
> added by this change that allow JVMCI compiler threads to communicate their "progress" to HotSpot:
> * Each JVMCI compiler thread has a "compilation ticks" counter.
> * There is also a global JVMCI compilation ticks counter.
> * Each JVMCI VM call increments the JVMCI compiler thread-local compilation ticks counter.
> * Every 512 increments of such a counter also increments the global counter.
> * A thread waiting on a blocking JVMCI compilation will be unblocked if these counters indicate no progress after a
>   defined period.

Looks good.

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PR: https://git.openjdk.java.net/jdk/pull/35