4 files changed, 135 insertions, 0 deletions
diff --git a/library/std/src/sys/unsupported/locks/condvar.rs b/library/std/src/sys/unsupported/locks/condvar.rs
new file mode 100644
index 000000000..e703fd0d2
--- /dev/null
+++ b/library/std/src/sys/unsupported/locks/condvar.rs
@@ -0,0 +1,27 @@
+use crate::sys::locks::Mutex;
+use crate::time::Duration;
+
+pub struct Condvar {}
+
+pub type MovableCondvar = Condvar;
+
+impl Condvar {
+    #[inline]
+    pub const fn new() -> Condvar {
+        Condvar {}
+    }
+
+    #[inline]
+    pub unsafe fn notify_one(&self) {}
+
+    #[inline]
+    pub unsafe fn notify_all(&self) {}
+
+    pub unsafe fn wait(&self, _mutex: &Mutex) {
+        panic!("condvar wait not supported")
+    }
+
+    pub unsafe fn wait_timeout(&self, _mutex: &Mutex, _dur: Duration) -> bool {
+        panic!("condvar wait not supported");
+    }
+}
diff --git a/library/std/src/sys/unsupported/locks/mod.rs b/library/std/src/sys/unsupported/locks/mod.rs
new file mode 100644
index 000000000..d412ff152
--- /dev/null
+++ b/library/std/src/sys/unsupported/locks/mod.rs
@@ -0,0 +1,6 @@
+mod condvar;
+mod mutex;
+mod rwlock;
+pub use condvar::{Condvar, MovableCondvar};
+pub use mutex::{MovableMutex, Mutex};
+pub use rwlock::{MovableRwLock, RwLock};
diff --git a/library/std/src/sys/unsupported/locks/mutex.rs b/library/std/src/sys/unsupported/locks/mutex.rs
new file mode 100644
index 000000000..d7cb12e0c
--- /dev/null
+++ b/library/std/src/sys/unsupported/locks/mutex.rs
@@ -0,0 +1,36 @@
+use crate::cell::Cell;
+
+pub struct Mutex {
+    // This platform has no threads, so we can use a Cell here.
+    locked: Cell<bool>,
+}
+
+pub type MovableMutex = Mutex;
+
+unsafe impl Send for Mutex {}
+unsafe impl Sync for Mutex {} // no threads on this platform
+
+impl Mutex {
+    #[inline]
+    pub const fn new() -> Mutex {
+        Mutex { locked: Cell::new(false) }
+    }
+
+    #[inline]
+    pub unsafe fn init(&mut self) {}
+
+    #[inline]
+    pub unsafe fn lock(&self) {
+        assert_eq!(self.locked.replace(true), false, "cannot recursively acquire mutex");
+    }
+
+    #[inline]
+    pub unsafe fn unlock(&self) {
+        self.locked.set(false);
+    }
+
+    #[inline]
+    pub unsafe fn try_lock(&self) -> bool {
+        self.locked.replace(true) == false
+    }
+}
diff --git a/library/std/src/sys/unsupported/locks/rwlock.rs b/library/std/src/sys/unsupported/locks/rwlock.rs
new file mode 100644
index 000000000..aca5fb715
--- /dev/null
+++ b/library/std/src/sys/unsupported/locks/rwlock.rs
@@ -0,0 +1,66 @@
+use crate::cell::Cell;
+
+pub struct RwLock {
+    // This platform has no threads, so we can use a Cell here.
+    mode: Cell<isize>,
+}
+
+pub type MovableRwLock = RwLock;
+
+unsafe impl Send for RwLock {}
+unsafe impl Sync for RwLock {} // no threads on this platform
+
+impl RwLock {
+    #[inline]
+    pub const fn new() -> RwLock {
+        RwLock { mode: Cell::new(0) }
+    }
+
+    #[inline]
+    pub unsafe fn read(&self) {
+        let m = self.mode.get();
+        if m >= 0 {
+            self.mode.set(m + 1);
+        } else {
+            rtabort!("rwlock locked for writing");
+        }
+    }
+
+    #[inline]
+    pub unsafe fn try_read(&self) -> bool {
+        let m = self.mode.get();
+        if m >= 0 {
+            self.mode.set(m + 1);
+            true
+        } else {
+            false
+        }
+    }
+
+    #[inline]
+    pub unsafe fn write(&self) {
+        if self.mode.replace(-1) != 0 {
+            rtabort!("rwlock locked for reading")
+        }
+    }
+
+    #[inline]
+    pub unsafe fn try_write(&self) -> bool {
+        if self.mode.get() == 0 {
+            self.mode.set(-1);
+            true
+        } else {
+            false
+        }
+    }
+
+    #[inline]
+    pub unsafe fn read_unlock(&self) {
+        self.mode.set(self.mode.get() - 1);
+    }
+
+    #[inline]
+    pub unsafe fn write_unlock(&self) {
+        assert_eq!(self.mode.replace(0), -1);
+    }
+}