Enter Unreachable code in Windows named pipe

[maxmicheluttiexelio]

Reached Unreachable code in Windows Named Pipe

I am developing a cross-platform daemon to handle multiple TTYACM devices in parallel.
In particular, I am leveraging serial2_tokio for serial communication and a mixture of tokio::sync::mpsc::channel and CancellationToken (from tokio_util) for communication between threads.
While everything works on both Linux and MacOS, on Windows I enter unreachable code at line 969 of mio/src/sys/windows/named_pipe.rs.
This happens inconsistently whenever I unplug multiple devices at once (in my tests, the minimum amount that triggered the issue is 3), becoming more consistent as the amount of devices I unplug together increases. I am unsure if the crash happens due to a serial port communication issue or a inter-thread communication issue, but I think the former possibility is much more likely.
I have been trying to produce a toy example that results in the crash, but I have not been successful yet. I willl update this issue as soon as I am able to do it.

2026-07-30T10:26:58Z [ERROR] (panic) thread 'tokio-rt-worker' panicked at 'internal error: entered unreachable code': /home/user/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/mio-1.2.2/src/sys/windows/named_pipe.rs:969
   0: backtrace::capture::Backtrace::create
   1: backtrace::capture::Backtrace::new
   2: log_panics::Config::install_panic_hook::{{closure}}
   3: myApp::main::{{closure}}::{{closure}}
   4: std::panicking::panic_with_hook
   5: std::panicking::panic_handler::{closure#0}
   6: std::sys::backtrace::__rust_end_short_backtrace::<std::panicking::panic_handler::{closure#0}, !>
   7: __rustc::rust_begin_unwind
   8: core::panicking::panic_fmt
   9: core::panicking::panic
  10: mio::sys::windows::named_pipe::write_done
  11: mio::sys::windows::selector::SelectorInner::select2
  12: mio::poll::Poll::poll
  13: tokio::runtime::io::driver::Driver::turn
  14: tokio::runtime::time::Driver::park_internal
  15: tokio::runtime::scheduler::multi_thread::worker::Context::park_internal
  16: tokio::runtime::scheduler::multi_thread::worker::Context::run
  17: tokio::runtime::context::scoped::Scoped<T>::set
  18: tokio::runtime::context::runtime::enter_runtime
  19: tokio::runtime::scheduler::multi_thread::worker::run
  20: tokio::runtime::task::core::Core<T,S>::poll
  21: tokio::runtime::task::harness::Harness<T,S>::poll
  22: tokio::runtime::blocking::pool::Inner::run
  23: std::sys::backtrace::__rust_begin_short_backtrace
  24: core::ops::function::FnOnce::call_once{{vtable.shim}}
  25: <std::sys::thread::windows::Thread>::new::thread_start
  26: <unknown>
  27: <unknown>

Environment

System: Dell Inspiron 5593 (x64-based)
Processor: Inter Core i5-1035G1 GPU @ 1.00GHz, 1190 MHz, 4 Core, 8 Logical Processors
OS: Microsoft Windows 11 Pro - 10.0.26200 Build 26200

rustc: 1.97
tokio: 1.53.1
mio: 1.2.2