thread/spinlock: don't try to lock during a move operation

thread/spinlock.cpp

@@ -30,14 +30,7 @@ spinlock::spinlock (spinlock &&rhs) noexcept:
 //-----------------------------------------------------------------------------
 spinlock& spinlock::operator= (spinlock &&rhs) noexcept
 {
-    lock ();
-    rhs.lock ();
-
     held = rhs.held.load ();
-
-    rhs.unlock ();
-    unlock ();
-
     return *this;
 }
 

thread/spinlock.hpp

@@ -3,22 +3,24 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
  *
- * Copyright 2018 Danny Robson <danny@nerdcruft.net>
+ * Copyright 2018-2019 Danny Robson <danny@nerdcruft.net>
  */
 
-#ifndef CRUFT_UTIL_THREAD_SPINLOCK_HPP
-#define CRUFT_UTIL_THREAD_SPINLOCK_HPP
+#pragma once
 
 #include <atomic>
 
 namespace cruft::thread {
-    /// a CPU intensive, but lower latency, lock.
+    /// A CPU intensive, but lower latency, lock.
     ///
     /// std::atomic_flag seems like it might have been a good option on which
     /// to base our implementation, but it appears potentially expensive to
     /// spin over without a cheap read operation.
     ///
-    /// satisfies BasicLockable.
+    /// Satisfies BasicLockable.
+    ///
+    /// NOTE: All move operations assume that either the lock is held by the
+    ///  client performing the move, or that is not held by any client.
     class spinlock {
     public:
         spinlock ();
@@ -40,5 +42,3 @@ namespace cruft::thread {
         std::atomic<bool> held;
     };
 };
-
-#endif