X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=includes%2FSMP.h;h=ac98feb7a3c2c7e55fd09e1567545ea9b3de2ee8;hb=88605454e4bf30d7fca2b0eea4643c5637afd5cc;hp=e3b4cd54a2bb71048207a580cdad344b2a8fc3e2;hpb=fa4e32f81bcfbba98ba7e9d5cb96a74b75b052da;p=ghc-hetmet.git

diff --git a/includes/SMP.h b/includes/SMP.h
index e3b4cd5..ac98feb 100644
--- a/includes/SMP.h
+++ b/includes/SMP.h
@@ -16,14 +16,6 @@
  *      Unregisterised builds are ok, but only 1 CPU supported.
  */
 
-#ifdef CMINUSMINUS
-
-#define unlockClosure(ptr,info)                 \
-    prim %write_barrier() [];                   \
-    StgHeader_info(ptr) = info;    
-
-#else
-
 #if defined(THREADED_RTS)
 
 #if  defined(TICKY_TICKY)
@@ -63,10 +55,22 @@ EXTERN_INLINE StgWord cas(StgVolatilePtr p, StgWord o, StgWord n);
 #endif // !IN_STG_CODE
 
 /*
- * Prevents write operations from moving across this call in either
- * direction.
+ * Various kinds of memory barrier.
+ *  write_barrier: prevents future stores occurring before prededing stores.
+ *  store_load_barrier: prevents future loads occurring before preceding stores.
+ *  load_load_barrier: prevents future loads occurring before earlier stores.
+ *
+ * Reference for these: "The JSR-133 Cookbook for Compiler Writers"
+ * http://gee.cs.oswego.edu/dl/jmm/cookbook.html
+ *
+ * To check whether you got these right, try the test in 
+ *   testsuite/tests/ghc-regress/rts/testwsdeque.c
+ * This tests the work-stealing deque implementation, which relies on
+ * properly working store_load and load_load memory barriers.
  */ 
 EXTERN_INLINE void write_barrier(void);
+EXTERN_INLINE void store_load_barrier(void);
+EXTERN_INLINE void load_load_barrier(void);
 
 /* ----------------------------------------------------------------------------
    Implementations
@@ -163,14 +167,10 @@ cas(StgVolatilePtr p, StgWord o, StgWord n)
 #endif // !IN_STG_CODE
 
 /*
- * Write barrier - ensure that all preceding writes have happened
- * before all following writes.  
- *
- * We need to tell both the compiler AND the CPU about the barrier.
- * This is a brute force solution; better results might be obtained by
- * using volatile type declarations to get fine-grained ordering
- * control in C, and optionally a memory barrier instruction on CPUs
- * that require it (not x86 or x86_64).
+ * We need to tell both the compiler AND the CPU about the barriers.
+ * It's no good preventing the CPU from reordering the operations if
+ * the compiler has already done so - hence the "memory" restriction
+ * on each of the barriers below.
  */
 EXTERN_INLINE void
 write_barrier(void) {
@@ -179,7 +179,42 @@ write_barrier(void) {
 #elif powerpc_HOST_ARCH
     __asm__ __volatile__ ("lwsync" : : : "memory");
 #elif sparc_HOST_ARCH
-    /* Sparc in TSO mode does not require write/write barriers. */
+    /* Sparc in TSO mode does not require store/store barriers. */
+    __asm__ __volatile__ ("" : : : "memory");
+#elif !defined(WITHSMP)
+    return;
+#else
+#error memory barriers unimplemented on this architecture
+#endif
+}
+
+EXTERN_INLINE void
+store_load_barrier(void) {
+#if i386_HOST_ARCH
+    __asm__ __volatile__ ("lock; addl $0,0(%%esp)" : : : "memory");
+#elif x86_64_HOST_ARCH
+    __asm__ __volatile__ ("lock; addq $0,0(%%rsp)" : : : "memory");
+#elif powerpc_HOST_ARCH
+    __asm__ __volatile__ ("sync" : : : "memory");
+#elif sparc_HOST_ARCH
+    __asm__ __volatile__ ("membar #StoreLoad" : : : "memory");
+#elif !defined(WITHSMP)
+    return;
+#else
+#error memory barriers unimplemented on this architecture
+#endif
+}
+
+EXTERN_INLINE void
+load_load_barrier(void) {
+#if i386_HOST_ARCH
+    __asm__ __volatile__ ("" : : : "memory");
+#elif x86_64_HOST_ARCH
+    __asm__ __volatile__ ("" : : : "memory");
+#elif powerpc_HOST_ARCH
+    __asm__ __volatile__ ("lwsync" : : : "memory");
+#elif sparc_HOST_ARCH
+    /* Sparc in TSO mode does not require load/load barriers. */
     __asm__ __volatile__ ("" : : : "memory");
 #elif !defined(WITHSMP)
     return;
@@ -191,7 +226,9 @@ write_barrier(void) {
 /* ---------------------------------------------------------------------- */
 #else /* !THREADED_RTS */
 
-#define write_barrier() /* nothing */
+#define write_barrier()      /* nothing */
+#define store_load_barrier() /* nothing */
+#define load_load_barrier()  /* nothing */
 
 INLINE_HEADER StgWord
 xchg(StgPtr p, StgWord w)
@@ -201,8 +238,17 @@ xchg(StgPtr p, StgWord w)
     return old;
 }
 
-#endif /* !THREADED_RTS */
+STATIC_INLINE StgWord
+cas(StgVolatilePtr p, StgWord o, StgWord n)
+{
+    StgWord result;
+    result = *p;
+    if (result == o) {
+        *p = n;
+    }
+    return result;
+}
 
-#endif /* CMINUSMINUS */
+#endif /* !THREADED_RTS */
 
 #endif /* SMP_H */