From 32b89eeba18d2d0a9c3705212768d4ade3f4948d Mon Sep 17 00:00:00 2001
From: Dario Nieuwenhuis <dirbaio@dirbaio.net>
Date: Thu, 12 Oct 2023 01:35:23 +0200
Subject: [PATCH] net: remove atomic-polyfill.

---
 cyw43/Cargo.toml                       |  1 -
 embassy-net/Cargo.toml                 |  1 -
 embassy-net/src/tcp.rs                 | 15 +++++++--------
 examples/stm32h7/src/bin/eth_client.rs |  4 ++--
 4 files changed, 9 insertions(+), 12 deletions(-)

diff --git a/cyw43/Cargo.toml b/cyw43/Cargo.toml
index dae7419c..c201405e 100644
--- a/cyw43/Cargo.toml
+++ b/cyw43/Cargo.toml
@@ -15,7 +15,6 @@ embassy-time = { version = "0.1.3", path = "../embassy-time"}
 embassy-sync = { version = "0.3.0", path = "../embassy-sync"}
 embassy-futures = { version = "0.1.0", path = "../embassy-futures"}
 embassy-net-driver-channel = { version = "0.1.0", path = "../embassy-net-driver-channel"}
-atomic-polyfill = "0.1.5"
 
 defmt = { version = "0.3", optional = true }
 log = { version = "0.4.17", optional = true }
diff --git a/embassy-net/Cargo.toml b/embassy-net/Cargo.toml
index c2fffba8..a3c18046 100644
--- a/embassy-net/Cargo.toml
+++ b/embassy-net/Cargo.toml
@@ -64,4 +64,3 @@ stable_deref_trait = { version = "1.2.0", default-features = false }
 futures = { version = "0.3.17", default-features = false, features = [ "async-await" ] }
 atomic-pool = "1.0"
 embedded-nal-async = { version = "0.6.0", optional = true }
-atomic-polyfill = { version = "1.0" }
diff --git a/embassy-net/src/tcp.rs b/embassy-net/src/tcp.rs
index a12fd382..b5615cb6 100644
--- a/embassy-net/src/tcp.rs
+++ b/embassy-net/src/tcp.rs
@@ -579,11 +579,10 @@ mod embedded_io_impls {
 /// TCP client compatible with `embedded-nal-async` traits.
 #[cfg(feature = "nightly")]
 pub mod client {
-    use core::cell::UnsafeCell;
+    use core::cell::{Cell, UnsafeCell};
     use core::mem::MaybeUninit;
     use core::ptr::NonNull;
 
-    use atomic_polyfill::{AtomicBool, Ordering};
     use embedded_nal_async::IpAddr;
 
     use super::*;
@@ -702,15 +701,13 @@ pub mod client {
         }
     }
 
-    unsafe impl<const N: usize, const TX_SZ: usize, const RX_SZ: usize> Sync for TcpClientState<N, TX_SZ, RX_SZ> {}
-
     struct Pool<T, const N: usize> {
-        used: [AtomicBool; N],
+        used: [Cell<bool>; N],
         data: [UnsafeCell<MaybeUninit<T>>; N],
     }
 
     impl<T, const N: usize> Pool<T, N> {
-        const VALUE: AtomicBool = AtomicBool::new(false);
+        const VALUE: Cell<bool> = Cell::new(false);
         const UNINIT: UnsafeCell<MaybeUninit<T>> = UnsafeCell::new(MaybeUninit::uninit());
 
         const fn new() -> Self {
@@ -724,7 +721,9 @@ pub mod client {
     impl<T, const N: usize> Pool<T, N> {
         fn alloc(&self) -> Option<NonNull<T>> {
             for n in 0..N {
-                if self.used[n].swap(true, Ordering::SeqCst) == false {
+                // this can't race because Pool is not Sync.
+                if !self.used[n].get() {
+                    self.used[n].set(true);
                     let p = self.data[n].get() as *mut T;
                     return Some(unsafe { NonNull::new_unchecked(p) });
                 }
@@ -738,7 +737,7 @@ pub mod client {
             let n = p.as_ptr().offset_from(origin);
             assert!(n >= 0);
             assert!((n as usize) < N);
-            self.used[n as usize].store(false, Ordering::SeqCst);
+            self.used[n as usize].set(false);
         }
     }
 }
diff --git a/examples/stm32h7/src/bin/eth_client.rs b/examples/stm32h7/src/bin/eth_client.rs
index 4db7aa25..09d27cdb 100644
--- a/examples/stm32h7/src/bin/eth_client.rs
+++ b/examples/stm32h7/src/bin/eth_client.rs
@@ -105,8 +105,8 @@ async fn main(spawner: Spawner) -> ! {
 
     info!("Network task initialized");
 
-    static STATE: TcpClientState<1, 1024, 1024> = TcpClientState::new();
-    let client = TcpClient::new(&stack, &STATE);
+    let state: TcpClientState<1, 1024, 1024> = TcpClientState::new();
+    let client = TcpClient::new(&stack, &state);
 
     loop {
         let addr = SocketAddr::V4(SocketAddrV4::new(Ipv4Addr::new(10, 42, 0, 1), 8000));