Add SelfContainedChannel #2757
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Add SelfContainedChannel #2757
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Thanks for the careful review! |
We're going to need to port additional synchronization primitives suitable for use in shared memory to Rust. I think conceptually it makes sense to put these in a crate together separate from the shared memory allocator, which isn't as closely related.
We'll want to reuse these for additional modules in this crate.
This is a VirtualAddressSpaceIndependent implementation of a channel. The intent is to use this to replace `BinarySpinningSem` and `IPCData` to communicate with managed threads from ManagedThread in Shadow.
The previous implementation had potential undefined behavior due to optimistically updating state without checking the previous state. We do away with the `fetch_add` and `fetch_sub` tricks here (with sanity checks after the fact), and instead use e.g. `compare_exchange`. This results in additional atomic operations in the "happy" path, but is easier to understand, especially in failure cases.
This is more general and more closely aligned with `std::mpsc::channel` terminology.
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We need a vasi (
VirtualAddressSpaceIndependent) wrapper or reimplementation ofIPCData(essentially a pair of fixed-size channels) for communication between shadow and the shim before migratingManagedThreadto Rust.This PR:
SelfContainedMutexinto a new crate, where we can putIPCDataand any other vasi sync primitives we end up needing to implement.SelfContainedMutexSelfContainedChanneland corresponding loom-compatible tests. It should be simple to replaceIPCDatawith a pair of these.