[project @ 2005-10-11 13:28:49 by simonpj]

[ghc-hetmet.git] / ghc / includes / SMP.h

diff --git a/ghc/includes/SMP.h b/ghc/includes/SMP.h
index 86930f9..cc95941 100644 (file)
--- a/ghc/includes/SMP.h
+++ b/ghc/includes/SMP.h
@@ -26,6 +26,9 @@
 /* 
  * XCHG - the atomic exchange instruction.  Used for locking closures
  * during updates (see LOCK_CLOSURE below) and the MVar primops.
+ *
+ * NB: the xchg instruction is implicitly locked, so we do not need
+ * a lock prefix here. 
  */
 INLINE_HEADER StgWord
 xchg(StgPtr p, StgWord w)
@@ -33,25 +36,50 @@ xchg(StgPtr p, StgWord w)
     StgWord result;
     result = w;
     __asm__ __volatile__ (
-         "xchgl %1,%0"
+         "xchg %1,%0"
           :"+r" (result), "+m" (*p)
           : /* no input-only operands */
        );
     return result;
 }
 
+/* 
+ * CMPXCHG - the single-word atomic compare-and-exchange instruction.  Used 
+ * in the STM implementation.
+ */
+INLINE_HEADER StgWord
+cas(StgVolatilePtr p, StgWord o, StgWord n)
+{
+    __asm__ __volatile__ (
+         "lock cmpxchg %3,%1"
+          :"=a"(o), "=m" (*(volatile unsigned int *)p) 
+          :"0" (o), "r" (n));
+    return o;
+}
+
 INLINE_HEADER StgInfoTable *
 lockClosure(StgClosure *p)
 {
+#if i386_HOST_ARCH || x86_64_HOST_ARCH
     StgWord info;
-#if 0
     do {
        info = xchg((P_)&p->header.info, (W_)&stg_WHITEHOLE_info);
        if (info != (W_)&stg_WHITEHOLE_info) return (StgInfoTable *)info;
        yieldThread();
     } while (1);
 #else
-    info = p->header.info;
+   ACQUIRE_SM_LOCK
+#endif
+}
+
+INLINE_HEADER void
+unlockClosure(StgClosure *p, StgInfoTable *info)
+{
+#if i386_HOST_ARCH || x86_64_HOST_ARCH
+    // This is safe enough, because lockClosure() does the memory barrier:
+    p->header.info = info;
+#else
+    RELEASE_SM_LOCK;
 #endif
 }