Do not #include external header files when compiling via C

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

diff --git a/includes/SpinLock.h b/includes/SpinLock.h
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+/* ----------------------------------------------------------------------------
+ *
+ * (c) The GHC Team, 2006-2008
+ *
+ * Spin locks
+ *
+ * These are simple spin-only locks as opposed to Mutexes which
+ * probably spin for a while before blocking in the kernel.  We use
+ * these when we are sure that all our threads are actively running on
+ * a CPU, eg. in the GC.
+ *
+ * TODO: measure whether we really need these, or whether Mutexes
+ * would do (and be a bit safer if a CPU becomes loaded).
+ *
+ * -------------------------------------------------------------------------- */
+
+#ifndef SPINLOCK_H
+#define SPINLOCK_H
+ 
+#if defined(THREADED_RTS)
+
+#if defined(DEBUG)
+typedef struct StgSync_
+{
+    StgWord32 lock;
+    StgWord64 spin; // DEBUG version counts how much it spins
+} StgSync;
+#else
+typedef StgWord StgSync;
+#endif
+
+typedef lnat StgSyncCount;
+
+
+#if defined(DEBUG)
+
+// Debug versions of spin locks maintain a spin count
+
+// How to use: 
+//  To use the debug veriosn of the spin locks, a debug version of the program 
+//  can be run under a deugger with a break point on stat_exit. At exit time 
+//  of the program one can examine the state the spin count counts of various
+//  spin locks to check for contention. 
+
+// acquire spin lock
+INLINE_HEADER void ACQUIRE_SPIN_LOCK(StgSync * p)
+{
+    StgWord32 r = 0;
+    do {
+        p->spin++;
+        r = cas((StgVolatilePtr)&(p->lock), 1, 0);
+    } while(r == 0);
+    p->spin--;
+}
+
+// release spin lock
+INLINE_HEADER void RELEASE_SPIN_LOCK(StgSync * p)
+{
+    write_barrier();
+    p->lock = 1;
+}
+
+// initialise spin lock
+INLINE_HEADER void initSpinLock(StgSync * p)
+{
+    write_barrier();
+    p->lock = 1;
+    p->spin = 0;
+}
+
+#else
+
+// acquire spin lock
+INLINE_HEADER void ACQUIRE_SPIN_LOCK(StgSync * p)
+{
+    StgWord32 r = 0;
+    do {
+        r = cas((StgVolatilePtr)p, 1, 0);
+    } while(r == 0);
+}
+
+// release spin lock
+INLINE_HEADER void RELEASE_SPIN_LOCK(StgSync * p)
+{
+    write_barrier();
+    (*p) = 1;
+}
+
+// init spin lock
+INLINE_HEADER void initSpinLock(StgSync * p)
+{
+    write_barrier();
+    (*p) = 1;
+}
+
+#endif /* DEBUG */
+
+#else /* !THREADED_RTS */
+
+// Using macros here means we don't have to ensure the argument is in scope
+#define ACQUIRE_SPIN_LOCK(p) /* nothing */
+#define RELEASE_SPIN_LOCK(p) /* nothing */
+
+INLINE_HEADER void initSpinLock(void * p STG_UNUSED)
+{ /* nothing */ }
+
+#endif /* THREADED_RTS */
+
+#endif /* SPINLOCK_H */
+