1 files changed, 77 insertions, 0 deletions
diff --git a/src/mongo/util/concurrency/spin_lock.h b/src/mongo/util/concurrency/spin_lock.h
new file mode 100644
index 00000000000..d90de51afac
--- /dev/null
+++ b/src/mongo/util/concurrency/spin_lock.h
@@ -0,0 +1,77 @@
+// spin_lock.h
+
+/**
+*    Copyright (C) 2008 10gen Inc.
+*
+*    This program is free software: you can redistribute it and/or  modify
+*    it under the terms of the GNU Affero General Public License, version 3,
+*    as published by the Free Software Foundation.
+*
+*    This program is distributed in the hope that it will be useful,
+*    but WITHOUT ANY WARRANTY; without even the implied warranty of
+*    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+*    GNU Affero General Public License for more details.
+*
+*    You should have received a copy of the GNU Affero General Public License
+*    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#pragma once
+
+#include "mutex.h"
+
+namespace mongo {
+
+    /**
+     * The spinlock currently requires late GCC support routines to be efficient.
+     * Other platforms default to a mutex implemenation.
+     */
+    class SpinLock : boost::noncopyable {
+    public:
+        SpinLock();
+        ~SpinLock();
+
+        static bool isfast(); // true if a real spinlock on this platform
+
+    private:
+#if defined(_WIN32)
+        CRITICAL_SECTION _cs;
+    public:
+        void lock() {EnterCriticalSection(&_cs); }
+        void unlock() { LeaveCriticalSection(&_cs); }
+#elif defined(__USE_XOPEN2K)
+        pthread_spinlock_t _lock;
+        void _lk();
+    public:
+        void unlock() { pthread_spin_unlock(&_lock); }
+        void lock() {
+            if ( pthread_spin_trylock( &_lock ) == 0 )
+                return;
+            _lk(); 
+        }
+#elif defined(__GCC_HAVE_SYNC_COMPARE_AND_SWAP_4)
+        volatile bool _locked;
+    public:
+        void unlock() {__sync_lock_release(&_locked); }
+        void lock();
+#else
+        // default to a mutex if not implemented
+        SimpleMutex _mutex;
+    public:
+        void unlock() { _mutex.unlock(); }
+        void lock() { _mutex.lock(); }
+#endif
+    };
+    
+    class scoped_spinlock : boost::noncopyable {
+    public:
+        scoped_spinlock( SpinLock& l ) : _l(l) {
+            _l.lock();
+        }
+        ~scoped_spinlock() {
+            _l.unlock();}
+    private:
+        SpinLock& _l;
+    };
+
+}  // namespace mongo