On Wed, 18 Feb 2026 10:32:52 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 without the fix, and no crashes > with the fix... Copyrights updated. Thanks! Years are passing way too fast. ------------- PR Comment: https://git.openjdk.org/valhalla/pull/2124#issuecomment-3920716727
