RFR: 8305913: com/sun/jdi/JdbLastErrorTest.java failed with "'lastError = 42' missing from stdout/stderr"

[David Holmes]

On Fri, 14 Apr 2023 19:23:05 GMT, Kevin Walls <kevinw at openjdk.org> wrote:

> This test is failing often since 8304725 added a call to Thread::current_in_asgct().  This can end up being called e.g. when resolving calls, and then the OS last error value is lost.
> 
> The test is reliable with a single warm-up call to getLastError.invoke() before the loop.
> 
> The test was introduced when in JDK-8292302 a change was undone that had made JavaThread::threadObj call Thread::current_or_null_safe, as the use of TLS upset this case of accessing last error directly.
> 
> This new Thread::current_in_asgct() case shows that the VM will find new ways to interfere with the last error value, or at least new VM code keeps wanting to call Thread::current.  This testcase is kind of niche usage, so it not an argument that VM code should not be calling Thread::current.   If this test is to stay active, it needs to have this warm-up getLastError call.  (If there are more issues, it might mean removing the test.)

Looks good - thanks for getting to the bottom of this failure! One suggestion below.

test/jdk/com/sun/jdi/JdbLastErrorTest.java line 63:

> 61:             FunctionDescriptor.ofVoid(ValueLayout.JAVA_INT));
> 62: 
> 63:         // One "warmup" call avoids VM activity (e.g. Thread::current) disturbing last error value.

Suggestion:

// Perform a "warmup" call to ensure method resolution can't disturb the last error value
// that we are trying to set.

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Marked as reviewed by dholmes (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/13481#pullrequestreview-1386348947
PR Review Comment: https://git.openjdk.org/jdk/pull/13481#discussion_r1167410330