* Added optional spinlock contention measurement feature. Enabled when

B_DEBUG_SPINLOCK_CONTENTION is defined to 1. It typedefs spinlock to a
  structure (thus breaking BeOS binary compatibility), containing a
  counter which is incremented whenever a thread has to wait for the
  spinlock.
* Added macros for spinlock initialization and access and changed
  code using spinlocks accordingly. This breaks compilation for BeOS --
  the macros should be defined in the respective compatibility wrappers.
* Added generic syscall to get the spinlock counters for the thread and
  the team spinlocks.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@25752 a95241bf-73f2-0310-859d-f6bbb57e9c96

headers/os/drivers/KernelExport.h

@@ -13,7 +13,32 @@
 /* interrupts and spinlocks */
 
 typedef ulong cpu_status;
-typedef vint32 spinlock;
+
+// WARNING: For Haiku debugging only! This changes the spinlock type in a
+// binary incompatible way!
+//#define B_DEBUG_SPINLOCK_CONTENTION	1
+
+#if B_DEBUG_SPINLOCK_CONTENTION
+	typedef struct {
+		vint32	lock;
+		vint32	count_low;
+		vint32	count_high;
+	} spinlock;
+
+#	define B_SPINLOCK_INITIALIZER { 0, 0, 0 }
+#	define B_INITIALIZE_SPINLOCK(spinlock)	do {	\
+			(spinlock)->lock = 0;					\
+			(spinlock)->count_low = 0;				\
+			(spinlock)->count_high = 0;				\
+		} while (false)
+#	define B_SPINLOCK_IS_LOCKED(spinlock)	((spinlock)->lock > 0)
+#else
+	typedef vint32 spinlock;
+
+#	define B_SPINLOCK_INITIALIZER 0
+#	define B_INITIALIZE_SPINLOCK(lock)	do { *(lock) = 0; } while (false)
+#	define B_SPINLOCK_IS_LOCKED(lock)	(*(lock) > 0)
+#endif
 
 /* interrupt handling support for device drivers */