If you run current test on 11u AArch64, then Shenandoah would fail:

$ CONF=linux-aarch64-normal-server-fastdebug make run-test TEST=compiler/c2/aarch64/TestVolatilesShenandoah.java

TEST RESULT: Failed. Execution failed: `main' threw exception: java.lang.RuntimeException: Missing expected output cmpxchgw?_acq_shenandoah!

This is because the 11.0.9 backport brought the test in broken form.

Compare for example:

master hunk:
  https://github.com/openjdk/jdk/blob/fb1dfc6f49f62990aa9988e9d6f7ffd1adf45d8e/test/hotspot/jtreg/compiler/c2/aarch64/TestVolatiles.java#L360-L371

11u hunk:
  https://github.com/openjdk/jdk11u-dev/blob/90d529355b0fa36ca3378efae8dc6ba4b5203869/test/hotspot/jtreg/compiler/c2/aarch64/TestVolatiles.java#L562-L573