> 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: the new ent...
Shiv Shah has updated the pull request incrementally with one additional commit since the last revision: Comments on the frozen frame checks and the two deoptimization paths ------------- Changes: - all: https://git.openjdk.org/jdk/pull/32661/files - new: https://git.openjdk.org/jdk/pull/32661/files/00b5aca5..519e0fab Webrevs: - full: https://webrevs.openjdk.org/?repo=jdk&pr=32661&range=06 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=32661&range=05-06 Stats: 4 lines in 1 file changed: 3 ins; 0 del; 1 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
