1 files changed, 62 insertions, 0 deletions
diff --git a/library/std/src/sys/sgx/mutex.rs b/library/std/src/sys/sgx/mutex.rs
new file mode 100644
index 000000000..513cd77fd
--- /dev/null
+++ b/library/std/src/sys/sgx/mutex.rs
@@ -0,0 +1,62 @@
+use super::waitqueue::{try_lock_or_false, SpinMutex, WaitQueue, WaitVariable};
+use crate::sys_common::lazy_box::{LazyBox, LazyInit};
+
+pub struct Mutex {
+    inner: SpinMutex<WaitVariable<bool>>,
+}
+
+// not movable: see UnsafeList implementation
+pub(crate) type MovableMutex = LazyBox<Mutex>;
+
+impl LazyInit for Mutex {
+    fn init() -> Box<Self> {
+        Box::new(Self::new())
+    }
+}
+
+// Implementation according to “Operating Systems: Three Easy Pieces”, chapter 28
+impl Mutex {
+    pub const fn new() -> Mutex {
+        Mutex { inner: SpinMutex::new(WaitVariable::new(false)) }
+    }
+
+    #[inline]
+    pub unsafe fn init(&mut self) {}
+
+    #[inline]
+    pub unsafe fn lock(&self) {
+        let mut guard = self.inner.lock();
+        if *guard.lock_var() {
+            // Another thread has the lock, wait
+            WaitQueue::wait(guard, || {})
+        // Another thread has passed the lock to us
+        } else {
+            // We are just now obtaining the lock
+            *guard.lock_var_mut() = true;
+        }
+    }
+
+    #[inline]
+    pub unsafe fn unlock(&self) {
+        let guard = self.inner.lock();
+        if let Err(mut guard) = WaitQueue::notify_one(guard) {
+            // No other waiters, unlock
+            *guard.lock_var_mut() = false;
+        } else {
+            // There was a thread waiting, just pass the lock
+        }
+    }
+
+    #[inline]
+    pub unsafe fn try_lock(&self) -> bool {
+        let mut guard = try_lock_or_false!(self.inner);
+        if *guard.lock_var() {
+            // Another thread has the lock
+            false
+        } else {
+            // We are just now obtaining the lock
+            *guard.lock_var_mut() = true;
+            true
+        }
+    }
+}