> 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 the interpreter > deopt entry after push_return_frame, the x86 deopt entry reloads rsp from > last_sp for that, aarch64 already does. 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 ca...
Shiv Shah has updated the pull request incrementally with two additional commits since the last revision: - Pass an int, a long and an Object through the popped frames and check them after reexecution - Require jvmti for the new PopFrames descriptors ------------- Changes: - all: https://git.openjdk.org/jdk/pull/32661/files - new: https://git.openjdk.org/jdk/pull/32661/files/3d4ad029..68b9f960 Webrevs: - full: https://webrevs.openjdk.org/?repo=jdk&pr=32661&range=02 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=32661&range=01-02 Stats: 34 lines in 5 files changed: 20 ins; 0 del; 14 mod Patch: https://git.openjdk.org/jdk/pull/32661.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/32661/head:pull/32661 PR: https://git.openjdk.org/jdk/pull/32661
