RFR: 8256050: JVM crashes with -XX:+PrintDeoptimizationDetails

[Daniel D.Daugherty]

On Mon, 9 Nov 2020 13:01:18 GMT, Vladimir Ivanov <vlivanov at openjdk.org> wrote:

> -XX:+PrintDeoptimizationDetails triggers intermittent crashes. I spotted 2 independent problems which the patch addresses:
>   * `markWord::print_on` doesn't handle displaced header case well (the pointer stored in the header may be stale);
>   * `InstanceKlass::oop_print_value_on` dumps some specific details about `MemberName`, but the code assumes the instance is fully initialized. It's necessarily the case: for example, deoptimization can happen when `MemberName` constructor is being executed.  
> 
> Testing:
> - [x] manually verified that the crashes go away -XX:+PrintDeoptimizationDetails
> - [x] hs-precheckin-comp,hs-tier1,hs-tier2

Looks good. Your call on whether to add the comment I proposed.

src/hotspot/share/runtime/basicLock.cpp line 34:

> 32:   markWord mark_word = displaced_header();
> 33:   if (mark_word.value() != 0) {
> 34:     bool print_monitor_info = (owner != NULL) && (owner->mark() == markWord::from_pointer((void*)this));

Could use a comment between L33 and L34:
// Print monitor info if there's an owning oop and it refers to this BasicLock.

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Marked as reviewed by dcubed (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/1124