On Wed, 2 Sep 2026 20:11:48 GMT, Shiv Shah <[email protected]> wrote: > When a virtual thread suspended at a breakpoint gets unmounted and mounted > again only the top frame is thawed. The caller stays frozen in the stack > chunk and the popped frame returns into the continuation return barrier. The > interpreter's popframe entry treats that return address like a deoptimized > caller, preserves the arguments, sets the reexecution bit and returns. The > barrier then thawed the caller as a plain return. Arguments and bit left > behind, no reexecution of the invoke, run() went on with a zero result. > > Thaw finishes it now. An interpreted caller gets the preserved arguments back > on its expression stack and its return slot is patched to a new popframe > reexecution entry of the interpreter, the mdp is set back to the invoke as > well. A compiled caller frozen in the chunk is deoptimized from > UpdateForPopTopFrameClosure::doit the same way set_frame_pop does it. Thaw > leaves the arguments alone in that case and unpack_on_stack puts them back. A > frozen compiled frame being popped stays opaque. > > A linkTo caller needs one more thing. The linker consumed the trailing > MemberName before the target ran and the preserved arguments are sized by the > target, so the MemberName is not among them. Thaw takes it from the caller's > local 0 the way the interpreter's popframe entry does, the lookup from > member_name_arg_or_null moved into a plain helper both can call. The > arguments go one slot up and the MemberName goes back on top. > > popframes002 runs popframes001 on a virtual thread with the join Chris > Plummer wrote enabled by a property in the debuggee. It unmounts the tested > thread before the breakpoint so the caller is frozen when popped, and run() > is excluded from compilation so this stays the interpreted case. popframes003 > is the compiled caller case, -Xcomp with the breakpoint in a separate stop() > so testedMethod keeps its compiled frame and run() stays frozen, the debugger > pops frame 1 and the debuggee checks with WhiteBox that run() and > testedMethod are compiled and that testedMethod ran twice. > -XX:+PreserveFramePointer keeps the thaw on the slow path. Both fail on > master without the hotspot change. popframes001 itself runs the plain case as > before and is off the virtual problem list. If separate copies of the > debugger and debuggee are preferred over the properties that is easy to > change. PopFrameMethodNameInvariantTest got an unmount mode, the same > linkToStatic pop on a virtual thread that sleeps before the breakpoint so its caller is frozen. > > Open: ppc and s39...
This pull request has now been integrated. Changeset: 7f9a2c57 Author: Shiv Shah <[email protected]> Committer: Serguei Spitsyn <[email protected]> URL: https://git.openjdk.org/jdk/commit/7f9a2c57a37980c1cd560d0d9578675ef075fc37 Stats: 623 lines in 25 files changed: 540 ins; 9 del; 74 mod 8391440: Test vmTestbase/nsk/jdwp/StackFrame/PopFrames/popframes001/TestDescription.java failed: Unexpected VM_DEATH event received: 99 (expected: 2) Co-authored-by: Chris Plummer <[email protected]> Reviewed-by: pchilanomate, sspitsyn ------------- PR: https://git.openjdk.org/jdk/pull/32661
