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Improve handling of nested continuations #54
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dhil
reviewed
Aug 16, 2023
| @@ -347,10 +368,24 @@ pub fn resume( | |||
| // entry of the payload store by virtue of using the array | |||
| // calling trampoline to execute it. | |||
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| // Restore tsp pointer in instance | |||
| let _tsp = TopOfStackPointer::as_raw(instance.tsp()); | |||
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Does this perform any side-effects? Can we remove it?
dhil
reviewed
Aug 16, 2023
crates/runtime/src/continuation.rs
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| let parent = unsafe { (*(*contobj).fiber).stack().parent() }; | ||
| instance.set_tsp(TopOfStackPointer::from_raw(parent)); | ||
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| debug_println!("Continuation @ {:p} returned normally, setting tsp from {:p} to {:p}", contobj, tsp, parent); | ||
| debug_println!("Continuation @ {:p} returned normally, setting tsp from {:p} to {:p}", contobj, _tsp, parent); |
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This PR improves the handling of nested continuations (i.e., invoking continuations within continuations).
It fixes two bugs:
FuncEnvironment::typed_continuations_load_continuation_object, we were incorrectly setting thereadonlyflag, which meant that multiple loads to the continuation object slot in theVMContextwere sometimes combined into one, even though the slot was overwritten in between.continuation::resume, we were not updating the top of stack (TSP) pointer in theVMInstanceafter returning from a continuation.This PR also adds debug printing to certain functions in
continuation.rs. Printing only happens in debug builds AND if the variableENABLE_DEBUG_PRINTINGin the same file is manually set to true. The printing goes through a macro to ensure that there is no chance of it affecting performance in release builds.This PR also adds various tests for nested uses of continuations, which also cover the two bugs mentioned earlier.