1 files changed, 57 insertions, 20 deletions

diff --git a/includes/rts/storage/SMPClosureOps.h b/includes/rts/storage/SMPClosureOps.h
index 39349874f7..a8ebb5d0ed 100644
--- a/includes/rts/storage/SMPClosureOps.h
+++ b/includes/rts/storage/SMPClosureOps.h
@@ -11,13 +11,27 @@
 
 #ifdef CMINUSMINUS
 
+/* Lock closure, equivalent to ccall lockClosure but the condition is inlined.
+ * Arguments are swapped for uniformity with unlockClosure. */
+#if defined(THREADED_RTS)
+#define LOCK_CLOSURE(closure, info)                             \
+    if (CInt[n_capabilities] == 1 :: CInt) {                    \
+        info = GET_INFO(closure);                               \
+    } else {                                                    \
+        ("ptr" info) = ccall reallyLockClosure(closure "ptr");  \
+    }
+#else
+#define LOCK_CLOSURE(closure, info) info = GET_INFO(closure)
+#endif
+
 #define unlockClosure(ptr,info)                 \
     prim_write_barrier;                         \
-    StgHeader_info(ptr) = info;    
+    StgHeader_info(ptr) = info;
 
 #else
 
-EXTERN_INLINE StgInfoTable *lockClosure(StgClosure *p);
+INLINE_HEADER StgInfoTable *lockClosure(StgClosure *p);
+EXTERN_INLINE StgInfoTable *reallyLockClosure(StgClosure *p);
 EXTERN_INLINE StgInfoTable *tryLockClosure(StgClosure *p);
 EXTERN_INLINE void unlockClosure(StgClosure *p, const StgInfoTable *info);
 
@@ -29,35 +43,58 @@ EXTERN_INLINE void unlockClosure(StgClosure *p, const StgInfoTable *info);
  * This is used primarily in the implementation of MVars.
  * -------------------------------------------------------------------------- */
 
-// We want a callable copy of lockClosure() so that we can refer to it
-// from .cmm files compiled using the native codegen.
-EXTERN_INLINE StgInfoTable *lockClosure(StgClosure *p)
+// We want a callable copy of reallyLockClosure() so that we can refer to it
+// from .cmm files compiled using the native codegen, so these are given
+// EXTERN_INLINE.  C-- should use LOCK_CLOSURE not lockClosure, so we've
+// kept it INLINE_HEADER.
+EXTERN_INLINE StgInfoTable *reallyLockClosure(StgClosure *p)
 {
     StgWord info;
     do {
-	nat i = 0;
-	do {
-	    info = xchg((P_)(void *)&p->header.info, (W_)&stg_WHITEHOLE_info);
-	    if (info != (W_)&stg_WHITEHOLE_info) return (StgInfoTable *)info;
-	} while (++i < SPIN_COUNT);
-	yieldThread();
+        nat i = 0;
+        do {
+            info = xchg((P_)(void *)&p->header.info, (W_)&stg_WHITEHOLE_info);
+            if (info != (W_)&stg_WHITEHOLE_info) return (StgInfoTable *)info;
+        } while (++i < SPIN_COUNT);
+        yieldThread();
     } while (1);
 }
 
+INLINE_HEADER StgInfoTable *lockClosure(StgClosure *p)
+{
+    if (n_capabilities == 1) {
+        return (StgInfoTable *)p->header.info;
+    }
+    else {
+        return reallyLockClosure(p);
+    }
+}
+
+// ToDo: consider splitting tryLockClosure into reallyTryLockClosure,
+// same as lockClosure
 EXTERN_INLINE StgInfoTable *tryLockClosure(StgClosure *p)
 {
     StgWord info;
-    info = xchg((P_)(void *)&p->header.info, (W_)&stg_WHITEHOLE_info);
-    if (info != (W_)&stg_WHITEHOLE_info) {
-        return (StgInfoTable *)info;
-    } else {
-        return NULL;
+    if (n_capabilities == 1) {
+        return (StgInfoTable *)p->header.info;
+    }
+    else {
+        info = xchg((P_)(void *)&p->header.info, (W_)&stg_WHITEHOLE_info);
+        if (info != (W_)&stg_WHITEHOLE_info) {
+            return (StgInfoTable *)info;
+        } else {
+            return NULL;
+        }
     }
 }
 
 #else /* !THREADED_RTS */
 
 EXTERN_INLINE StgInfoTable *
+reallyLockClosure(StgClosure *p)
+{ return (StgInfoTable *)p->header.info; }
+
+INLINE_HEADER StgInfoTable *
 lockClosure(StgClosure *p)
 { return (StgInfoTable *)p->header.info; }
 
@@ -75,12 +112,12 @@ EXTERN_INLINE void unlockClosure(StgClosure *p, const StgInfoTable *info)
 }
 
 // Handy specialised versions of lockClosure()/unlockClosure()
-EXTERN_INLINE void lockTSO(StgTSO *tso);
-EXTERN_INLINE void lockTSO(StgTSO *tso)
+INLINE_HEADER void lockTSO(StgTSO *tso);
+INLINE_HEADER void lockTSO(StgTSO *tso)
 { lockClosure((StgClosure *)tso); }
 
-EXTERN_INLINE void unlockTSO(StgTSO *tso);
-EXTERN_INLINE void unlockTSO(StgTSO *tso)
+INLINE_HEADER void unlockTSO(StgTSO *tso);
+INLINE_HEADER void unlockTSO(StgTSO *tso)
 { unlockClosure((StgClosure*)tso, (const StgInfoTable *)&stg_TSO_info); }
 
 #endif /* CMINUSMINUS */