Changeset 1714

Timestamp:

09/11/10 16:09:05 (3 years ago)

Author:

ahu

Message:

thanks to RHEL5/CENTOS5.. we now have assembly in PowerDNS. "Thanks". Spotted by Bas && Imre Gergely.

Files:

• trunk/pdns/pdns/misc.hh (modified) (2 diffs)

trunk/pdns/pdns/misc.hh

@@ -351 +351 @@
     explicit AtomicCounter( unsigned int v = 0) : value_( v ) {}
 
-    void operator++()
+    unsigned int operator++()
     {
-        __sync_add_and_fetch( &value_, 1 );
+      return atomic_exchange_and_add( &value_, +1 ) + 1;
     }
 
     unsigned int operator--()
     {
-        return __sync_add_and_fetch( &value_, -1 );
+      return atomic_exchange_and_add( &value_, -1 ) - 1;
     }
 
     operator unsigned int() const
     {
-        return __sync_fetch_and_add( &value_, 0 );
+      return atomic_exchange_and_add( &value_, 0);
     }
 
@@ -371 +371 @@
 
     mutable unsigned int value_;
+    
+    // the below is necessary because __sync_fetch_and_add is not universally available on i386.. I 3> RHEL5. 
+    #if defined( __GNUC__ ) && ( defined( __i386__ ) || defined( __x86_64__ ) )
+    static int atomic_exchange_and_add( unsigned int * pw, int dv )
+    {
+        // int r = *pw;
+        // *pw += dv;
+        // return r;
+
+        int r;
+
+        __asm__ __volatile__
+        (
+            "lock\n\t"
+            "xadd %1, %0":
+            "+m"( *pw ), "=r"( r ): // outputs (%0, %1)
+            "1"( dv ): // inputs (%2 == %1)
+            "memory", "cc" // clobbers
+        );
+
+        return r;
+    }
+    #else 
+    static int atomic_exchange_and_add( unsigned int * pw, int dv )
+    {
+      return __sync_fetch_and_add(pw, dv);
+    }
+    #endif
 };