On Wed, 18 Feb 2026 13:05:32 GMT, Marc Chevalier <[email protected]> wrote:
>> In `SharedRuntime::get_resolved_entry` when `current->is_interp_only_mode()` >> we need to go to the interpreter, and thus we must always return a c2i >> adapter (and not the entry point of another compiled method). >> >> https://github.com/openjdk/valhalla/blob/d5e3620d5a0b13cce9c19bafd5b2dd881b8bf9e9/src/hotspot/share/runtime/sharedRuntime.cpp#L1635-L1641 >> >> Yet, here, we disregard the kind of call, or the caller. Yet, under, we make >> the correct distinction: >> >> https://github.com/openjdk/valhalla/blob/d5e3620d5a0b13cce9c19bafd5b2dd881b8bf9e9/src/hotspot/share/runtime/sharedRuntime.cpp#L1643-L1652 >> >> Indeed, if the caller is C1, the call won't be scalarized, so we don't need >> the packing logic that would be required for a scalarized call from C2, for >> instance... Overall, we must distinguish the 3 same cases as when >> `is_interp_only_mode` is not set. The only difference is that instead of >> picking the compiled entry point if available, and only an adapter as a >> fallback, we must take the adapter. Right now, the code is correct only if >> `!caller_does_not_scalarize && (is_static_call || is_optimized)` (so, >> especially not calls from C1). >> >> I've slightly changed the shape of the code to make that more clear, and >> also to be less likely to forget a case if we add new variations in the >> calling convention! >> >> If this error doesn't show up so often, that's because >> `is_interp_only_mode()` is only set by JVMTI: >> >> https://github.com/openjdk/valhalla/blob/d5e3620d5a0b13cce9c19bafd5b2dd881b8bf9e9/src/hotspot/share/prims/jvmtiThreadState.cpp#L322-L328 >> and >> https://github.com/openjdk/valhalla/blob/d5e3620d5a0b13cce9c19bafd5b2dd881b8bf9e9/src/hotspot/share/prims/jvmtiThreadState.inline.hpp#L151-L153 >> >> So, without JVMTI, it is impossible to observe this bug, which is >> unfortunate. So, how to test that, not to do the same error again? A test >> involving JVMTI would be brittle, and we can do better than adding yet >> another test: making better usage of existing tests. Now, >> `StressCallingConvention` will sometimes make `get_resolved_entry` behaves >> as if `is_interp_only_mode` is set. Doing so causes SO MANY crashes in >> `TestCallingConventionC1`, which is expected. With the fix, it works again >> as expected. >> >> The frequency of `is_interp_only_mode` being randomly true when stressing is >> currently set at a very arbitrary 1/2^10 which is around 0.1%. I've also >> tested with a probability of 1/2, and I get basically the same behavior: >> plenty of crashes with the improved stress wi... > > Marc Chevalier has updated the pull request incrementally with one additional > commit since the last revision: > > Copyright Thanks for review! ------------- PR Comment: https://git.openjdk.org/valhalla/pull/2124#issuecomment-3920853365
