1 files changed, 91 insertions, 0 deletions
diff --git a/ghc/includes/SMP.h b/ghc/includes/SMP.h
new file mode 100644
index 0000000000..fa247988cf
--- /dev/null
+++ b/ghc/includes/SMP.h
@@ -0,0 +1,91 @@
+/* ----------------------------------------------------------------------------
+ * $Id: SMP.h,v 1.1 1999/11/02 15:05:52 simonmar Exp $
+ *
+ * (c) The GHC Team, 1999
+ *
+ * Macros for SMP support
+ *
+ * -------------------------------------------------------------------------- */
+
+#ifndef SMP_H
+#define SMP_H
+
+/* SMP is currently not compatible with the following options:
+ *
+ *      INTERPRETER
+ *      PROFILING
+ *      TICKY_TICKY
+ *      and unregisterised builds.
+ */
+
+#if defined(SMP)
+
+#if    defined(INTERPRETER) \
+     || defined(PROFILING)  \
+     || defined(TICKY_TICKY)
+#error Build options incompatible with SMP.
+#endif
+
+/*
+ * CMPXCHG - this instruction is the standard "test & set".  We use it
+ * for locking closures in the thunk and blackhole entry code.  If the
+ * closure is already locked, or has an unexpected info pointer
+ * (because another thread is altering it in parallel), we just jump
+ * to the new entry point.
+ */
+#if defined(i386_TARGET_ARCH) && defined(TABLES_NEXT_TO_CODE)
+#define CMPXCHG(p, cmp, new)			\
+  __asm__ __volatile__ (  			\
+	  "lock ; cmpxchg %1, %0\n"		\
+          "\tje 1f\n"				\
+          "\tjmp *%%eax\n"			\
+          "\t1:\n"				\
+	  : /* no outputs */			\
+	  : "m" (p), "r" (new), "r" (cmp)	\
+	  )
+
+/* 
+ * XCHG - the atomic exchange instruction.  Used for locking closures
+ * during updates (see LOCK_CLOSURE below) and the MVar primops.
+ */
+#define XCHG(reg, obj)				\
+  __asm__ __volatile__ (			\
+ 	  "xchgl %1,%0"				\
+          :"+r" (reg), "+m" (obj)		\
+          : /* no input-only operands */	\
+	  )
+
+#else
+#error SMP macros not defined for this architecture
+#endif
+
+/*
+ * LOCK_CLOSURE locks the specified closure, busy waiting for any
+ * existing locks to be cleared.
+ */
+#define LOCK_CLOSURE(c)					\
+  ({							\
+    const StgInfoTable *__info;				\
+    __info = &WHITEHOLE_info;				\
+    do {						\
+      XCHG(__info,((StgClosure *)(c))->header.info);	\
+    } while (__info == &WHITEHOLE_info);		\
+    __info;						\
+  })
+
+#define LOCK_THUNK(__info)				\
+  CMPXCHG(R1.cl->header.info, __info, &WHITEHOLE_info);
+
+#define ACQUIRE_LOCK(mutex) pthread_mutex_lock(mutex);
+#define RELEASE_LOCK(mutex) pthread_mutex_unlock(mutex);
+
+#else /* !SMP */
+
+#define LOCK_CLOSURE(c)     /* nothing */
+#define LOCK_THUNK(__info)  /* nothing */
+#define ACQUIRE_LOCK(mutex) /* nothing */
+#define RELEASE_LOCK(mutex) /* nothing */
+
+#endif /* SMP */
+
+#endif /* SMP_H */