Do not use DEFINE_RWLOCK Macro

diff -r ef25e071a074 unmodified_drivers/linux-2.6/platform-pci/machine_reboot.c
@@ -15,8 +15,10 @@ struct ap_suspend_info {
 /*
  * Use a rwlock to protect the hypercall page from being executed in AP context
  * while the BSP is re-initializing it after restore.
+ * Do not use the DEFINE_RWLOCK macro, as it is not available when compiled against
+ *  older kernels
  */
-static DEFINE_RWLOCK(suspend_lock);
+static rwlock_t suspend_lock = RW_LOCK_UNLOCKED;
 
 /*
  * Spinning prevents, for example, APs touching grant table entries while

diff -r a381118a247a unmodified_drivers/linux-2.6/compat-include/xen/platform-compat.h
@@ -116,4 +116,13 @@ extern char *kasprintf(gfp_t gfp, const 
 #define DEFINE_SEQLOCK(x) seqlock_t x = SEQLOCK_UNLOCKED
 #endif
 
+#if defined(__LINUX_SPINLOCK_H) && !defined(DEFINE_RWLOCK)
+#define DEFINE_RWLOCK(x) rwlock_t x = RW_LOCK_UNLOCKED
 #endif
+
+/* Bug in RHEL4-U3 rw_lock_t is mistakenly defined in this macro */
+#if defined(__LINUX_SPINLOCK_H) && defined(DEFINE_RWLOCK)
+#define rw_lock_t rwlock_t
+#endif
+
+#endif