[jdk8u-dev] RFR: 8339133: [8u] Profiler crashes at guarantee(is_result_safe || is_in_asgct()): unsafe access to zombie method

[Andrei Pangin]

When running AsyncGetCallTrace based profiler, JVM occasionally crashes on the guarantee at codeCache.cpp:287:

guarantee(is_result_safe || is_in_asgct(), "unsafe access to zombie method");

According to the stack trace, a thread is inside `AsyncGetCallTrace` at the moment of crash, but `is_in_asgct() == false`.

Current implementation of `AsyncGetCallTrace` is not reentrant, since it incorrectly resets `in_asgct` flag of the current thread. The fix is similar to [JDK-8329103](https://bugs.openjdk.org/browse/JDK-8329103): `in_asgct` should be reset to previous value instead of `false`.

The fix is trivial and safe: it affects only `AsyncGetCallTrace`.

Testing: tier1, renaissance suite with async-profiler enabled

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Commit messages:
 - 8339133: [8u] Profiler crashes at guarantee(is_result_safe || is_in_asgct()): unsafe access to zombie method

Changes: https://git.openjdk.org/jdk8u-dev/pull/568/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk8u-dev&pr=568&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8339133
  Stats: 3 lines in 1 file changed: 1 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk8u-dev/pull/568.diff
  Fetch: git fetch https://git.openjdk.org/jdk8u-dev.git pull/568/head:pull/568

PR: https://git.openjdk.org/jdk8u-dev/pull/568