Only in linux-2.6.17smp/include/asm-sparc: asm-offsets.h
diff -ur linux-2.6.16/include/asm-sparc/spinlock.h linux-2.6.17smp/include/asm-sparc/spinlock.h
--- linux-2.6.16/include/asm-sparc/spinlock.h	2006-05-27 19:35:16.000000000 +0200
+++ linux-2.6.17smp/include/asm-sparc/spinlock.h	2006-05-27 21:33:28.000000000 +0200
@@ -154,6 +154,8 @@
 #define __raw_spin_lock_flags(lock, flags) __raw_spin_lock(lock)
 #define __raw_read_trylock(lock) generic__raw_read_trylock(lock)
 
+#define __raw_write_can_lock(rw)	(!(rw)->lock)
+
 #endif /* !(__ASSEMBLY__) */
 
 #endif /* __SPARC_SPINLOCK_H */