RFR: 8278053: serviceability/jvmti/vthread/ContStackDepthTest/ContStackDepthTest.java failing in loom repo with Xcomp

[Coleen Phillimore]

On Tue, 14 Jun 2022 08:02:21 GMT, Ron Pressler <rpressler at openjdk.org> wrote:

> Please review the following fix.
> 
> When JVM TI puts a thread's state in `interp_only_mode`, thaw takes the slow path and deoptimizes frames as they're thawed in `recurse_thaw_compiled_frame`. However, thawing a deoptimized frame's callee will override the frame's patched pc (to the deopt handler), essentially reverting the deoptimization. This fix patches the deoptimized return address after thawing the callee.
> 
> Passes loom tiers 1-5

src/hotspot/share/runtime/continuationFreezeThaw.cpp line 1970:

> 1968:   } else {
> 1969:     // caller might have been deoptimized during thaw but we've overwritten the return address when copying f
> 1970:     ContinuationHelper::Frame::patch_pc(caller, caller.raw_pc());

What is raw_pc() vs pc() ?  why? is _cont.is_empty() true here? ie. a bit more explanation would be useful here.

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PR: https://git.openjdk.org/jdk19/pull/12