General cleanup

.github/workflows/miri.yml

@@ -5,17 +5,18 @@ on: [push, pull_request]
 env:
   CARGO_TERM_COLOR: always
   CARGO_NET_GIT_FETCH_WITH_CLI: true
+  DEFAULT_MIRI_FLAGS: -Zmiri-ignore-leaks -Zmiri-symbolic-alignment-check -Zmiri-retag-fields=all -Zmiri-symbolic-alignment-check -Zmiri-strict-provenance -Zmiri-disable-isolation -Zmiri-tree-borrows -Zmiri-track-raw-pointers
 
 jobs:
   miri:
     runs-on: ubuntu-latest
     env:
-      RUSTFLAGS: ${{ matrix.rustflags }}
+      RUSTFLAGS: --cfg tokio_unstable ${{matrix.rustflags}}
     strategy:
       matrix:
         toolchain: ["nightly-2023-09-01"]
         seed: [1, 2, 3, 4, 5, 6, 7, 8]
-        rustflags: ["--cfg mfio_assume_linear_types --cfg tokio_unstable", "--cfg tokio_unstable"]
+        rustflags: ["", "--cfg mfio_assume_linear_types"]
     steps:
       - uses: actions/checkout@v2
       - uses: actions-rs/toolchain@v1
@@ -25,4 +26,4 @@ jobs:
       - run: rustup component add miri
       - name: Run miri
         run: |
-          MIRIFLAGS="-Zmiri-seed=${{ matrix.seed }} -Zmiri-ignore-leaks -Zmiri-symbolic-alignment-check -Zmiri-retag-fields=all -Zmiri-symbolic-alignment-check -Zmiri-strict-provenance -Zmiri-disable-isolation -Zmiri-tree-borrows" cargo miri test
+          MIRIFLAGS="-Zmiri-seed=${{matrix.seed}} ${{env.DEFAULT_MIRI_FLAGS}}" cargo miri test

mfio-rt/src/native/impls/mod.rs

@@ -14,21 +14,3 @@ pub mod iocp;
 
 #[cfg(all(not(miri), unix, feature = "mio"))]
 pub mod mio;
-
-cfg_if::cfg_if! {
-    if #[cfg(miri)] {
-        // Force use thread impl if on miri
-        pub use thread::*;
-    } else if #[cfg(all(target_os = "linux", feature = "io-uring"))] {
-        // io-uring provides true completion I/O, however, it's Linux-only.
-        pub use self::io_uring::*;
-    } else if #[cfg(all(unix, feature = "mio"))] {
-        // mio allows for true async io
-        // however, we are relying on file descriptors here, so we can't expose it on non-unix
-        // platforms.
-        pub use self::mio::*;
-    } else {
-        // Fallback to thread on any unmatched cases
-        pub use thread::*;
-    }
-}

mfio-rt/src/native/mod.rs

@@ -494,10 +494,6 @@ impl NativeRt {
         self.block_on(func(self))
     }
 
-    fn register_file(&self, file: std::fs::File) -> NativeFile {
-        self.cwd.instance.register_file(file)
-    }
-
     /// Registers a non-seekable I/O stream
     pub fn register_stream(&self, stream: TcpStream) -> NativeTcpStream {
         self.cwd.instance.register_stream(stream)

mfio/src/io/mod.rs

@@ -187,7 +187,7 @@ impl<'a, T: PacketIo<Perms, Param>, Perms: PacketPerms, Param, Pkt: PacketStore<
     type Output = Pkt::StackReq<'a>;
 
     fn poll(self: Pin<&mut Self>, cx: &mut Context) -> Poll<Self::Output> {
-        let state: &Self = unsafe { core::mem::transmute(self) };
+        let state = self.into_ref().get_ref();
 
         loop {
             match unsafe { (*state.initial_state.get()).take() } {
@@ -244,7 +244,7 @@ impl<
     > IoToFut<'a, T, Perms, Param, Pkt, Out>
 {
     pub fn submit(self: Pin<&mut Self>) -> &Out::StackReq<'a> {
-        let state: &Self = unsafe { core::mem::transmute(self) };
+        let state = unsafe { self.get_unchecked_mut() };
 
         if let Some((io, param)) = unsafe { (*state.initial_state.get()).take() } {
             // SAFETY: this packet's existence is tied to 'a lifetime, meaning it will be valid

mfio/src/io/packet/mod.rs

@@ -103,13 +103,11 @@ impl RcAndWaker {
     }
 
     pub fn wait_finalize(&self) {
-        // FIXME: in theory, wait_finalize should only wait for the FINALIZED_BIT, but not deal
-        // with the locking and the waker. However, something is making us have to take the waker,
-        // to make these atomic ops sound (however, even then I doubt this is fully sound, but is
-        // merely moving probability of desync lower).
-        // Either way, we should be able to have this waker mechanism be way more optimized,
-        // without atomic locks.
-        self.take();
+        // When we are holding data on the stack, this synchronization is somehow needed to avoid
+        // data races. To be fair, it is unlikely that this is eliminating them completely, but it
+        // probably pushes the statistical probability enough to not trigger it.
+        #[cfg(mfio_assume_linear_types)]
+        let _ = self.take();
         while (self.rc_and_flags.load(Ordering::Acquire) & FINALIZED_BIT) == 0 {
             core::hint::spin_loop();
         }