Merge branch 'master' of github.com:mongodb/mongo

guanqun · Oct 14, 2011 · 127251f · 127251f
2 parents 44115bd + 92624b2
commit 127251f
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Showing 2 changed files with 27 additions and 36 deletions.
diff --git a/util/concurrency/spin_lock.cpp b/util/concurrency/spin_lock.cpp
@@ -16,7 +16,7 @@
 *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-#include "pch.h"
+#include "pch.h" // todo eliminate this include
 #include <time.h>
 #include "spin_lock.h"
 
@@ -41,11 +41,8 @@ namespace mongo {
     : _mutex( "SpinLock" ) { }
 #endif
 
-    void SpinLock::lock() {
-#if defined(_WIN32)
-        EnterCriticalSection(&_cs);
-#elif defined(__USE_XOPEN2K)
-
+#if defined(__USE_XOPEN2K)
+    NOINLINE_DECL void SpinLock::_lk() {
         /**
          * this is designed to perform close to the default spin lock
          * the reason for the mild insanity is to prevent horrible performance
@@ -54,12 +51,11 @@ namespace mongo {
          * which is good because even with this change they are about 8x faster on linux
          */
 
-        if ( pthread_spin_trylock( &_lock ) == 0 )
-            return;
-
-        for ( int i=0; i<1000; i++ ) 
+        for ( int i=0; i<1000; i++ ) {            
             if ( pthread_spin_trylock( &_lock ) == 0 )
                 return;
+            asm volatile ( "pause" ) ; // maybe trylock does this; just in case.
+        }
 
         for ( int i=0; i<1000; i++ ) {
             if ( pthread_spin_trylock( &_lock ) == 0 )
@@ -74,8 +70,10 @@ namespace mongo {
         while ( pthread_spin_trylock( &_lock ) != 0 ) {
             nanosleep(&t, NULL);
         }
-            
+    }
 #elif defined(__GCC_HAVE_SYNC_COMPARE_AND_SWAP_4)
+    void SpinLock::lock() {
+
         // fast path
         if (!_locked && !__sync_lock_test_and_set(&_locked, true)) {
             return;
@@ -94,32 +92,11 @@ namespace mongo {
         while (__sync_lock_test_and_set(&_locked, true)) {
             nanosleep(&t, NULL);
         }
-#else
-        // WARNING Missing spin lock in this platform. This can potentially
-        // be slow.
-        _mutex.lock();
-
-#endif
     }
-
-    void SpinLock::unlock() {
-#if defined(_WIN32)
-        LeaveCriticalSection(&_cs);
-#elif defined(__USE_XOPEN2K)
-        pthread_spin_unlock(&_lock);
-#elif defined(__GCC_HAVE_SYNC_COMPARE_AND_SWAP_4)
-        __sync_lock_release(&_locked);
-#else
-        _mutex.unlock();
 #endif
-    }
 
     bool SpinLock::isfast() {
-#if defined(_WIN32)
-        return true;
-#elif defined(__USE_XOPEN2K)
-        return true;
-#elif defined(__GCC_HAVE_SYNC_COMPARE_AND_SWAP_4)
+#if defined(_WIN32) || defined(__USE_XOPEN2K) || defined(__GCC_HAVE_SYNC_COMPARE_AND_SWAP_4)
         return true;
 #else
         return false;

diff --git a/util/concurrency/spin_lock.h b/util/concurrency/spin_lock.h
@@ -31,21 +31,35 @@ namespace mongo {
         SpinLock();
         ~SpinLock();
 
-        void lock();
-        void unlock();
-
         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
     };