Use our own AtomicU64 on targets with target_has_atomic less than 64

Author: taiki-e

.github/workflows/ci.yml

@@ -46,6 +46,39 @@ jobs:
         command: test
         args: --all --features unstable
 
+  cross:
+    name: Cross compile
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        target:
+          - i686-unknown-linux-gnu
+          - powerpc-unknown-linux-gnu
+          - powerpc64-unknown-linux-gnu
+          - mips-unknown-linux-gnu
+          - arm-linux-androideabi
+
+    steps:
+    - uses: actions/checkout@master
+
+    - name: Install nightly
+      uses: actions-rs/toolchain@v1
+      with:
+        toolchain: nightly
+        override: true
+
+    - name: Install cross
+      run: cargo install cross
+
+    - name: check
+      run: cross check --all --target ${{ matrix.target }}
+
+    - name: check unstable
+      run: cross check --all --features unstable --target ${{ matrix.target }}
+
+    - name: test
+      run: cross test --all --features unstable --target ${{ matrix.target }}
+
   check_fmt_and_docs:
     name: Checking fmt and docs
     runs-on: ubuntu-latest

src/sync/atomic.rs

@@ -0,0 +1,43 @@
+pub(crate) use self::imp::AtomicU64;
+
+// `AtomicU64` can only be used on targets with `target_has_atomic` is 64 or greater.
+// Once `cfg_target_has_atomic` feature is stable, we can replace it with
+// `#[cfg(target_has_atomic = "64")]`.
+// Refs: https://github.com/rust-lang/rust/tree/master/src/librustc_target
+#[cfg(not(any(target_arch = "arm", target_arch = "mips", target_arch = "powerpc")))]
+mod imp {
+    pub(crate) use std::sync::atomic::AtomicU64;
+}
+
+#[cfg(any(target_arch = "arm", target_arch = "mips", target_arch = "powerpc"))]
+mod imp {
+    use std::sync::atomic::Ordering;
+    use std::sync::Mutex;
+
+    #[derive(Debug)]
+    pub(crate) struct AtomicU64(Mutex<u64>);
+
+    impl AtomicU64 {
+        pub(crate) fn new(val: u64) -> Self {
+            Self(Mutex::new(val))
+        }
+
+        pub(crate) fn load(&self, _: Ordering) -> u64 {
+            *self.0.lock().unwrap()
+        }
+
+        pub(crate) fn fetch_add(&self, val: u64, _: Ordering) -> u64 {
+            let mut lock = self.0.lock().unwrap();
+            let prev = *lock;
+            *lock = prev + val;
+            prev
+        }
+
+        pub(crate) fn fetch_sub(&self, val: u64, _: Ordering) -> u64 {
+            let mut lock = self.0.lock().unwrap();
+            let prev = *lock;
+            *lock = prev - val;
+            prev
+        }
+    }
+}

src/sync/mod.rs

@@ -181,6 +181,7 @@ pub use std::sync::{Arc, Weak};
 pub use mutex::{Mutex, MutexGuard};
 pub use rwlock::{RwLock, RwLockReadGuard, RwLockWriteGuard};
 
+pub(crate) mod atomic;
 mod mutex;
 mod rwlock;
 

src/task/blocking.rs

@@ -1,17 +1,23 @@
 //! A thread pool for running blocking functions asynchronously.
 
-use std::sync::atomic::{AtomicU64, Ordering};
+use std::sync::atomic::Ordering;
 use std::thread;
 use std::time::Duration;
 
 use crossbeam_channel::{bounded, Receiver, Sender};
 use once_cell::sync::Lazy;
 
+use crate::sync::atomic::AtomicU64;
 use crate::task::task::{JoinHandle, Tag};
 use crate::utils::abort_on_panic;
 
 const MAX_THREADS: u64 = 10_000;
 
+#[cfg(any(target_arch = "arm", target_arch = "mips", target_arch = "powerpc"))]
+lazy_static! {
+    static ref DYNAMIC_THREAD_COUNT: AtomicU64 = AtomicU64::new(0);
+}
+#[cfg(not(any(target_arch = "arm", target_arch = "mips", target_arch = "powerpc")))]
 static DYNAMIC_THREAD_COUNT: AtomicU64 = AtomicU64::new(0);
 
 struct Pool {

src/task/task.rs

@@ -4,10 +4,11 @@ use std::i64;
 use std::mem;
 use std::num::NonZeroU64;
 use std::pin::Pin;
-use std::sync::atomic::{AtomicU64, AtomicUsize, Ordering};
+use std::sync::atomic::{AtomicUsize, Ordering};
 use std::sync::Arc;
 
 use super::task_local;
+use crate::sync::atomic::AtomicU64;
 use crate::task::{Context, Poll};
 
 /// A handle to a task.
@@ -112,6 +113,11 @@ pub struct TaskId(NonZeroU64);
 
 impl TaskId {
     pub(crate) fn new() -> TaskId {
+        #[cfg(any(target_arch = "arm", target_arch = "mips", target_arch = "powerpc"))]
+        lazy_static::lazy_static! {
+            static ref COUNTER: AtomicU64 = AtomicU64::new(1);
+        }
+        #[cfg(not(any(target_arch = "arm", target_arch = "mips", target_arch = "powerpc")))]
         static COUNTER: AtomicU64 = AtomicU64::new(1);
 
         let id = COUNTER.fetch_add(1, Ordering::Relaxed);